Mixing Enthalpy for Binary Mixtures Containing Ionic Liquids

Review pubs.acs.org/CR

Mixing Enthalpy for Binary Mixtures Containing Ionic Liquids A. Podgoršek,† J. Jacquemin,*,†,‡ A. A. H. Pádua,† and M. F. Costa Gomes*,† †

Equipe Thermodynamique et Interactions Moléculaires, Institut de Chimie de Clermont-Ferrand, UMR CNRS 6296, 24 Avenue des Landais, BP 80026, 63177 Aubière Cedex, France ‡ School of Chemistry and Chemical Engineering, Queen’s University Belfast, Stranmillis Road, Belfast BT9 5AG, United Kingdom S Supporting Information *

ABSTRACT: A complete review of the published data on the mixing enthalpies of mixtures containing ionic liquids, measured directly using calorimetric techniques, is presented in this paper. The field of ionic liquids is very active and a number of research groups in the world are dealing with different applications of these fluids in the fields of chemistry, chemical engineering, energy, gas storage and separation or materials science. In all these fields, the knowledge of the energetics of mixing is capital both to understand the interactions between these fluids and the different substrates and also to establish the energy and environmental cost of possible applications. Due to the relative novelty of the field, the published data is sometimes controversial and recent reviews are fragmentary and do not represent a set of reliable data. This fact can be attributed to different reasons: (i) difficulties in controlling the purity and stability of the ionic liquid samples; (ii) availability of accurate experimental techniques, appropriate for the measurement of viscous, charged, complex fluids; and (iii) choice of an appropriate clear thermodynamic formalism to be used by an interdisciplinary scientific community. In this paper, we address all these points and propose a critical review of the published data, advise on the most appropriate apparatus and experimental procedure to measure this type of physical-chemical data in ionic liquids as well as the way to treat the information obtained by an appropriate thermodynamic formalism.

CONTENTS 1. Introduction 2. Formalism and Data Treatment 3. Experimental Methods 3.1. Enthalpy of Solution and Enthalpy of Mixing 3.2. Partial Molar Excess Enthalpy 4. Enthalpies of Mixing and Partial Molar Excess Enthalpies 4.1. (Ionic Liquid + Ionic Liquid) Binary Mixtures 4.2. (Ionic Liquid + Associating Compound) Binary Mixtures 4.3. (Ionic Liquid + Nonassociative Compound) Binary Mixtures 5. Conclusions Associated Content Supporting Information Author Information Corresponding Authors Notes Biographies Acknowledgments List of Abbreviations List of Symbols References

involving ionic liquids. This review is focused on mixing enthalpies, solution enthalpies, and partial molar excess enthalpies that have been determined directly using different calorimetric methods and, to the best of our knowledge, published in the literature until May 2015. [All the major literature databases were covered (Science Finder, Scopus, and Web of Knowledge) and the database on ionic liquid properties, NIST Standard Reference Database no. 147 (ILThermo v2.0), was verified.] Energetic properties of mixing are relevant both in fundamental and application contexts. At the fundamental level, enthalpic quantities of mixing are closely related to the nature of molecular or ionic interactions and to the microscopic structure of mixtures. Applications may concern both contributions from thermodynamics and thermochemistry to other scientific disciplines such as chemistry, materials or environmental sciences, and also inputs to industrial applications, namely chemical processes or devices involving ionic liquids. Ionic liquids are composed of organic ions that have certain characteristics that hinder crystallization, and therefore, these salts are liquid near room temperature. In general, at least one of the ions is bulky, asymmetric, flexible, has delocalized electrostatic charge, low charge density, contains nonpolar tails, or combinations of these factors. Any of these characteristics contributes to increase the complexity of molecular interactions present in ionic liquid systems1 and may also introduce significant structural effects at the microscopic level.2 Pure

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1. INTRODUCTION This work presents a systematic overview of the results on enthalpy changes in mixing (or dissolution) processes in systems © 2016 American Chemical Society

Received: July 1, 2015 Published: May 4, 2016 6075

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The field of thermodynamic properties of ionic liquids has reached a degree of maturity, with a large body of results available in the literature. Purity issues that posed difficulties in earlier studies have been largely solved in recent years, through adoption of appropriate synthetic routes, best practices in the characterization of samples, and some round-robin exercises13 for evaluation of uncertainties. This review has the objectives of analyzing this body of literature and to evaluate the mutual consistency of different measurements. Section 2 of this review presents the thermodynamic formalism used in the analysis of the literature data and how they were statistically analyzed. Section 3 of this review contains a description of the experimental techniques used by several authors to describe ionic liquid binary systems, together with the thermodynamic quantities accessed. Only (liquid + liquid) binary systems with at least one component being an ionic liquid are reviewed, although some examples of ternary systems are included14 as well as some determinations of heat of dissolution of solid salts in ionic liquids.15−17 The aim of this work is to analyze and critically evaluate the consistency of published data both from a numerical and from a thermodynamic point of view. This evaluation was made by checking the thermodynamic consistency of the data and also by comparing the data for the same system reported by different research groups. All published experimental results are treated herein using the same numerical approach, which facilitates the comparison of the calculated mixing enthalpies and the partial molar excess enthalpies. The data reported on binary mixtures includes 5279 experimental values of the enthalpy change of mixing published in 65 articles18−63,81−101 available in the literature until 2015. Six different types of calorimeters, adiabatic,18−20 Calvet-type (refs 21−35, 83, 84, 92, 94, 95, 98, and 100), isothermal flow calorimeters,36−43,88 isothermal titration calorimeters (refs 44−51, 85, 93, 96, 97, 99, and 101), isoperibol (refs 43, 52−63, 81, 82, 86, 87, 89, and 91), and differential calorimeters,90 are used by the different authors. The data include 375 data sets at different temperatures (from 278 to 413 K) and at pressures up to 2.4 MPa corresponding to 194 binary systems, −49 molecular compounds mixed with 72 ionic liquids. The ionic liquids include 9 families of cations (imidazolium, pyridinium, pyrrolidinium, ammonium, triazolium, morpholonium, piperidinium, isoquinolium, and phosphonium) associated with 28 different anions. The majority of the published studies (46 papers) concern ionic liquids based on 1-alkyl-3-methylimidazolium cations with different anions (43 different ionic liquids). Other cations, like pyridinium (4 ionic liquids in 7 papers), pyrrolidinium (4 ionic liquids in 6 papers), ammonium (13 ionic liquids in 9 papers), and phosphonium (1 ionic liquid in 1 paper) are much less studied. The 5 most common anions are bis(trifluoromethylsulfonyl)imide NTf2−, tetrafluoroborate BF4−, trifluoromethanesulfonate TfO−, hexafluorophosphate PF6−, and ethylsulfate C2SO4−. The majority of published data sets concern binary systems containing water, methanol, and ethanol, in (137, 32, and 36) data sets corresponding to (37, 9, and 10)% of the covered literature, respectively. In section 4, the collected data are systematically presented. With this purpose, the compounds mixed with the ionic liquids are classified as ionic, associating, or nonassociating depending on their molecular nature and on the interactions they might establish with the ionic liquid. This review indicates that there are a number of systems, which require further investigation in order to get accurate insight on the energetics of mixing in binary systems involving ionic liquids.

ionic liquids have a strong, persistent structure due, first, to charge ordering of the ions that is the characteristic structure of an ionic fluid3 and, second, to a degree of segregation between nonpolar alkyl chains and charged head groups of the ions.4 Both types of structural characteristics affect the solvation of compounds and the properties of mixtures.5−7 An enormous variety of chemical structures can be used to create ionic liquids with properties adapted to specific applications.8 In order to understand the physical and chemical properties of ionic liquids and to be able to design the most suitable compounds in view of applications, it is paramount to establish structure−property relations connecting structure and interactions at the molecular level to macroscopic thermodynamic and transport properties. Concerning energetic thermodynamic quantities, the most important ones are related to the cohesive energy of ionic liquids and to the mixing of ionic liquids with other compounds. The cohesive energy issue has been the subject of studies that yielded several interesting findings, among them the realization that the enthalpy of vaporization of ionic liquids is determined to a significant extent by dispersive, van der Waals forces on par with electrostatic interactions.9,10 This is because when an ionic liquid vaporizes, it is ion pairs that compose the gas phase and removal of an ion pair from the liquid involves disrupting van der Waals and Coulomb interactions of comparable energies. The understanding of the energetics of mixing ionic liquids with molecular compounds is less advanced. These are mixture properties and intrinsically more diverse than pure fluid properties. According to the nature of the molecular compound with respect to their interactions, nonpolar, polar, associative involving hydrogen bonds, quite different mixing properties are expected with ionic liquids, both in terms of energetics and structure of the mixtures. It was shown by molecular simulation that ionic liquids that exhibit segregation between ionic and nonpolar regions offer different solvation environments to solutes, according to the nature of the last.1,5 Mixtures of ionic liquids may pass through different regimes when spanning the concentration range between the pure ionic and the molecular compound (or as far as mutual miscibility will allow). At low concentrations of molecular compound, its molecules will be isolated and solvated in an ionic medium. At the other extreme of concentration, isolated ions or ion pairs will be solvated in a molecular medium (essentially electrolyte systems). But at intermediate concentrations, the structure of the mixtures can be complex, with situations in which both ionic and molecular “microphases” percolate the system. These different concentration regimes should be related to the behavior of mixing properties and to the miscibility limits. Therefore, the complexity of ionic liquids and the large differences between their pure fluid properties and those of the molecular compounds lead to complex mixtures. Our understanding of these requires a systematic overview of energetic properties of mixing. Concerning the closely related volumetric properties of mixing, it happens that ionic liquids have volumetric properties that are almost additive,11,12 which is certainly a consequence of their high cohesive energy and low free volume. Several groupcontribution schemes for prediction of volumetric properties have been proposed in which the molar volume of the ionic liquid is decomposed into a sum of cation, and anion volumes and contributions of functional groups to the molar volume of the individual ions are largely independent of the cation−anion pair that composes a specific ionic liquid (e.g., good transferability). 6076

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2. FORMALISM AND DATA TREATMENT Because terminology and nomenclature are delicate but essential aspects of thermodynamics, we define here the main quantities used in the present review. The total enthalpy change upon mixing is the enthalpy difference between the resulting mixture of a certain composition and the pure compounds, all in the same physical state (here liquid), temperature, and pressure. This enthalpy change is an extensive quantity that corresponds to the heat of mixing measured in a calorimeter at constant temperature and pressure. Δmix H t ≡ H t −

∑ Hit = nH − ∑ niHi = nΔmix H i

i

enthalpy, the partial molar quantity and partial molar excess quantity are numerically identical Hi = H̅ iE . Partial excess enthalpy of a component i in a mixture, H̅ iE is defined as the enthalpy change when at constant temperature and pressure i is added to a mixture at constant composition. ⎛ ∂(n + n2)Δmix H ⎞ H̅ 2E = ⎜ 1 ⎟ ∂n2 ⎠n , p , T ⎝ 1

⎛ ∂(n + n2)Δmix H ⎞ H1̅ E = ⎜ 1 ⎟ ∂n1 ⎠n ⎝

(1)

where the superscript t denotes an extensive quantity, n = ∑ini is the amount of substance of the mixture and of its components, and H and Hi are the molar enthalpies of the mixture and of the pure substances. Usually, when speaking of enthalpy of mixing, it is the intensive (molar) quantity that is referred to. Δmix H = H −

∑ xiHi

where xi are the mole fractions of the components. Since there is no absolute reference scale for enthalpy, the enthalpies of the pure components can be chosen as zero, and in this case ΔmixH = H, the excess enthalpy of mixing is the difference between the enthalpy of mixing of a real mixture and that of an ideal mixture. Since the enthalpy of mixing of an ideal mixture is zero by definition, the excess enthalpy is numerically identical to the enthalpy of mixing. HE ≡ Δmix H − Δmix H id = Δmix H

Δmix H = x 2Δsol H = (1 − x1)Δsol H

The partial molar enthalpy of a component at a certain composition in the mixture is the enthalpy change upon addition of an amount of that component to the system:

j≠i , T , p

(4)

This partial derivative is always taken from an extensive quantity while keeping the amounts of all other components constant. The molar enthalpy of the mixture is an additive property of the partial molar enthalpies, H=

∑ xiH̅i

(9)

To enable the comparison of the experimental data, the values of ΔmixH were fitted to Redlich−Kister eqs (eqs 10 and 11)16 to access the parameters Ai and hence allow the calculation of H̅ iE as a function of composition using eqs 12 and 13. The experimentally determined ΔsolH (reported molalities were converted to mole fractions of ionic liquid) were fitted to eq 11. In both cases, values of partial molar excess enthalpies at infinite dilution were obtained by extrapolating H̅ iE to xi = 0 and therefore simply determined from eqs 14 and 15. When the solute is injected in small amounts in the solvent at constant temperature and pressure (as in titration methods explained below), the partial excess enthalpy of solute, H̅ 2E is assessed directly. In this case, the experimental data were fitted to eq 12, which is merely the derivative of the Redlich−Kister fit (eq 10).

(3)

⎛ ∂(nH ) ⎞ H̅ i = ⎜ ⎟ ⎝ ∂ni ⎠n

(8)

2 ,p,T

In the literature are reported either values of enthalpies of solution, ΔsolH, enthalpies of mixing, ΔmixH, or of partial molar excess enthalpies, H̅ iE . ΔsolH refers to the heat effect when a certain amount of a solute is dissolved in a solvent and is normally reported in energy per quantity of solute and expressed as a function of molality, m, whereas ΔmixH is always expressed in energy per mole of mixture. Both quantities are related by eq 9, where xi are the mole fractions of the constituents of the mixture. (Herein we have considered 1 as the ionic liquid and 2 the molecular compound, unless indicated otherwise.)

(2)

i

and

n

Δmix H = (1 − x 2)x 2 ∑ Ai (1 − 2x 2)i = (1 − x1)x1 i=0 n

(5)

i

∑ Ai(2xi − 1)i

In an analogous manner to eq 4, a partial molar excess enthalpy of mixing can be defined,

n

⎛ ∂(nHE) ⎞ H̅ iE ≡ ⎜ ⎟ ⎝ ∂ni ⎠n

i=0

(6)

⎛ ∂(nH E) ⎞ =⎜ ⎟ ⎝ ∂ni ⎠n

j≠i , T , p

⎛ ∂(nΔmix H ) ⎞ =⎜ ⎟ ∂ni ⎝ ⎠

i=0

(11)

It follows from eq 1, 3, and 4 that

j≠i , T , p

n

Δsol H = (1 − x 2) ∑ Ai (1 − 2x 2)i = x1 ∑ Ai (2x1 − 1)i

j≠i , T , p

⎛ ∂(nH ) ⎞ H̅ i ≡ ⎜ ⎟ ⎝ ∂ni ⎠n

(10)

i=0

⎛ ∂Δ H ⎞ H̅ 2E = Δmix H + (1 − x 2)⎜ mix ⎟ ⎝ ∂x 2 ⎠ p,T,x

+ Hi

1

nj ≠ i , T , p

⎛ n = (x 2 − 1)2 ⎜⎜x 2 ∑ −2iAi (1 − 2x 2)−1 + i ⎝ i=0

+ Hi = H̅ iE + Hi (7)

n

+

Once more, the choice of Hi = 0 simplifies the relations between partial molar enthalpy and the enthalpy of mixing. In the case of

i=0

6077

⎞

∑ Ai(1 − 2x2)i ⎟⎟ ⎠

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⎛ ∂Δ H ⎞ = Δmix H + (1 + x1)⎜ mix ⎟ ⎝ ∂x1 ⎠ p , T , x

H1̅ E

n

σ H2̅ E = (x 2 − 1)4 2

2

σ H2̅ E = (x1 − 1)4

⎞ + ∑ Ai (2x1 − 1)i ⎟⎟ ⎠ i=0

1

x2 → 0

=

(20)

1

= lim

x1→ 0

H1̅ E

=

1 N

∑ (−1) Ai

(15)

i=0

N

∑ (Yi ,calc − Yi ,exp)2 (16)

i=0

where N and Y represent, respectively, the number of data and the property to which the coefficients are adjusted, either ΔmixH or H̅ iE . It is always possible to improve the fit by using a Redlich− Kister polynomial with a higher degree. However, the number of fitting parameters Ai in eqs 10 or 11 should be as small as possible while reproducing closely the composition dependence of the property, to avoid introducing unphysical behavior into the fitting equations. The number of fitting parameters was always kept significantly smaller than the number of experimental points, as can be verified in the database included in the Supporting Information. Furthermore, the number of parameters was selected based on the value of the standard deviation of the fit and also by keeping the individual statistical uncertainty of each individual parameter at least 1 order of magnitude smaller than its absolute value. The uncertainty associated with each thermodynamic property Y was calculated using eq 17, where σY is the standard deviation. The contribution due to the uncertainty in mole fraction was assumed to be negligible in comparison with the error associated with each Ai parameter. The error bars in the calculated enthalpy of mixing and in the partial molar excess enthalpies and partial molar excess enthalpies at infinite dilution were estimated according to eq 18 to 21. σY2

⎛ ∂Y ⎞2 2 ⎛ ∂Y ⎞2 2 = ∑⎜ ⎟ σ A + ⎜ ⎟ σx ≈ ∂Ai ⎠ i ⎝ ∂xi ⎠ i i ⎝ = (1 −

x 2)2 x 22

⎛ ∂Y ⎞2 2 ∑ ⎜ ⎟ σ Ai ∂Ai ⎠ i ⎝

∑ (1 − 2x2)2i σ A2

(17)

i

= (1 − x1)2

i=0

i=0

(21)

The measurement of the heat changes corresponding to the dissolution of small concentrations (10−5 < x2 < 10−3) of a solute in a solvent allows the direct determination of the molar enthalpy of solution or the enthalpy of solution, ΔsolH, commonly expressed in terms of the amount of solute. The values of ΔsolH are measured in adiabatic or isoperibol solution calorimeters. Both types of solution calorimeters operate in a heat accumulation principle, meaning that the temperature of the sample rises for exothermic and decreases for endothermic processes, respectively. In general, solution calorimeters contain a single batch measuring system and are operated in a static mode. In adiabatic solution calorimeters, the sample and the surroundings are at the same temperature (TS = TE), which

n

x12 ∑ (2x1 − 1)2i σ A2i

i

i=0

3.1. Enthalpy of Solution and Enthalpy of Mixing

n

σΔ2mix H

∑ σ A2

3. EXPERIMENTAL METHODS Enthalpy changes in mixing (or dissolution) processes are determined either directly, using different calorimetric methods, or indirectly through the measurement of the activity coefficients or of the vapor pressure. In this review, only mixing enthalpies that were determined calorimetrically of ionic liquids mixed with other liquids (ionic or molecular compounds) are reported. A plethora of calorimetric methods exist to measure the heat effect when the sample under investigation undergoes a change from an initial to a final state.64 The large variety of calorimeter designs makes their classification in systematic groups difficult.65,66 If we consider that every calorimeter is constituted by two regions, the sample and the surroundings, the sample region, at the temperature TS, refers not only to the sample under investigation but also to the associated containers, heaters, and thermometers, whereas the surroundings concerns the controlled region around the sample with a temperature TE. In a calorimetric experiment TS, TE and their difference, ΔT = TS − TE, are measured as a function of time. The main differences between the calorimeters commonly used concern the principle of the measurement (heat compensating, heat accumulating, and heat exchange); the mode of operation (isothermal, adiabatic, and isoperibol); the principle of the construction (single measurement and twin differential measurement); the temperature distribution (static and dynamic); the movement of the sample (static−batch or dynamic−flow); and the temperature control (active, Peltier unit or passive, heat sink). In all cases, the heat effect associated with the dissolution of a small amount of a component 2 (solute) in another designated as 1 (solvent, where x2 ≪ x1) or with the mixing of both components at various molar ratios (to cover all the composition range) can be expressed either by an enthalpy of solution, ΔsolH, an enthalpy of mixing, ΔmixH, or a partial molar excess enthalpy, H̅ iE .

i

Furthermore, it is considered that the molar enthalpy of solution for the ionic liquid at infinite dilution, ΔsolH∞, calculated from eqs 14 and 15, equals the standard molar enthalpy of solution, and also the partial excess enthalpy of the ionic liquid at infinite dilution, ΔsolH∞ = ΔsolH0 = H1̅ E, ∞. The fit of the parameters Ai was performed by least-squares minimization using the standard deviation as an objective function: σ=

2

(14)

i=0

n

H1̅ E, ∞

i

n

σ H2̅ E,∞ = σ H2̅ E,∞ =

∑ Ai

2

∑ (2ix1(2x1 − 1)i− 1 + (2x1 − 1)i ) σ A2 i=0

(13)

n

= lim

(19) n

n

H̅ 2E

i=0

σ A2i

⎛ n = (x1 − 1)2 ⎜⎜x1 ∑ 2iAi (2x1 − 1)−1 + i ⎝ i=0

H̅ 2E, ∞

∑ (−2ix2(1 − 2x2)i− 1 + (1 − 2x2)i )2

(18) 6078

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Figure 1. Schematic representation of adiabatic (a)67 and isoperibol (b)69 solution calorimeter.

Figure 2. (a) Schematic representation of an isothermal Calvet condution calorimeter.65 (b) Modified cells in Calvet condution calorimeter used by Navia et al.31 (c) Modified cells in Setaram Calvet-MS 80 calorimeter used by Ortega et al.32

may change during the experiment (ΔT = 0, TS ≠ const). All the main elements of the adiabatic calorimeter (Figure 1a),67 the sample cell, the thermistor, the stirrer, and the heating element, are enclosed within a Dewar flask or in other similar adiabatic setup equipped with a vacuum insulation gasket used to reduce undesirable heat conduction, the temperature of the surrounding wall being maintained as close as possible to that of the sample. The calorimetric vessels used have a relatively large internal volume and are made of appropriate materials in order to reduce thermal gradients (for example, a 330 cm3 calorimetric vessel made of Pt−Ir alloy plated with silver18). For the enthalpy of solution measurements, a glass device containing one of the components is broken after thermal equilibration18 while in the mixing enthalpy determinations, one liquid is poured directly into the other.19,20 Adiabatic calorimeters can be calibrated chemically, by measuring excess enthalpy of a known system (e.g., water and diethylene glycol19,20) or electrically, by allowing a controlled amount of electrical energy to be converted to heat, Qel in the calorimeter thus inducing a temperature change, ΔTel.18 The enthalpy of solution, ΔsolH, is calculated from the observed temperature change, ΔTmeas, using eq 9. Spurious heat effects related to the evaporation of the solvent into the void volume of the sample cell or owed to the friction caused by stirring can be compensated and corrected. The accuracy and the precision of the measurements using adiabatic solution calorimeters,

estimated on the basis of the temperature uncertainty, are of the order of ±0.1%.18 Δsol H =

Q el ΔTel

ΔTmeas

(22)

Very few data for ionic liquid systems have been reported so far using adiabatic solution calorimeters. The enthalpy of solution of small quantities of [C1C8Im][BF4] in water18,68 and the enthalpies of mixing of [C1C1Im][DMP]19 and [C1C2Im][DMP]20 with water, methanol, and ethanol over all composition range were measured using this type of calorimeter. When an adiabatic solution calorimeter is placed in a thermostatic bath, its surroundings are kept at constant temperature, while the sample temperature may change (ΔT ≠ 0, TE = const). These solution calorimeters are normally designated as isoperibol solution calorimeters and are schematically represented in Figure 1b. The calorimetric vessel is typically relatively large (a 100−200 mL glass-plated silver Dewar69 or 90 mL glass vessel43,63), the elements being similar to those of an adiabatic calorimeter: a 469 or 1 mL43−63 glass sample cell, a twinblade stirrer,43 a heater, a thermistor, an amplifier, and an A/D converter. The liquid thermostatic baths are used with temperature controls as precise as ±0.00143,69 or ±0.0002 K,63 the temperature being read to within 3 × 10−543 or 10−4 K.69 The enthalpy of solution is measured when a given amount of a solute (0.1 to 4 g) retained in a sealed glass ampule, thermally 6079

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Figure 3. (a) Schematic representation of a twin type of flow mixing calorimeter.64,65 (b−d) Schematic diagram of flow system. S and R denote sample and reference cell, respectively. (b) Mode for calibration of heat loss. (c) Delay mode for determination of heat capacity of pure liquid. (d) Direct mixing mode for determination of excess heat capacity of mixture.

dense and viscous fluids and to avoid undesirable heat effects due to stirring. A homemade design, described by Romani ́ and collaborators,26−29,31 is represented in Figure 2b and allows a more effective stirring of the mixtures containing ionic liquids. The undesirable heat effects caused by a vigorous stirring, necessary to reach a stable baseline, are corrected by means of a blank experiment. The uncertainty of the experimentally determined excess molar enthalpies of two alkylimidazolium ionic liquids31 and of one alkylimidazolium ionic liquid with water,26 ethanol,27,29 or nitromethane28,29 is estimated as 4%. Commercial calorimeters have also been adapted to study mixtures of high density and viscosity like those containing methylpyridinium-based ionic liquids. In Figure 2c is represented a modified cell of a Setaram Calvet-MS 80 twin-calorimeter where an empty stainless-steel cylinder with several holes on its surface is used as a stirrer. In this case, the heat effects related to stirring are considered negligible and the enthalpy of mixing of 1butyl-2-methylpyridinium tetrafluoroborate with water and 1alkanols30,32,33 is considered accurate to within 1%. When a Setaram C80 isothermal calorimeter operating in differential scanning mode is used for the determination of the enthalpies of mixing of ionic liquids with water,23−25 the difference in the heat flow between the sample cell and an empty reference vessel is accurately measured by heat flow transducers that completely surround the two vessels, their temperature being maintained by Peltier elements. The two liquids are first separated by mercury and then mixed by rotating the entire vessel by 180°, stirring being guaranteed by the movement of a mobile stainless steel lid. The experimental uncertainty associated with this method was estimated to be 2%.

equilibrated in the calorimetric vessel, is put into contact with the solvent by breaking the whole glass ampule43,63 or by disrupting a sealing plastic film.69 The corrected temperature changes and the enthalpies of solution are calculated from eq 22. Calorimeters can be tested by measuring the molar enthalpy of solution of a known system, usually KCl in water (standard reference material 1655 by NIST).43,69 Isoperibol solution calorimeters, either homemade53−63 or commercial models,43 have been used to measure the enthalpy of solution of various ionic liquids in water. Enthalpies of mixing can also be measured directly using (batch) isothermal Calvet calorimeters. A Calvet calorimeter consists of two static batch cells, one filled with the sample and the other with a reference fluid (twin measurement principle). The two cells are usually placed in symmetrical positions in a massive metal block, which works as a heat sink (Figure 2a).66 The measuring principle is heat conduction, meaning that the heat liberated from a system, when known amounts of two substances are mixed, is conducted to a thermostated component (heat sink) through a thermo-element (thermomodule or thermopile) placed between each cell and the heat sink. The difference between the heat flowing from the sample and the reference cell generates an electric signal, which is measured with a voltmeter, converted to a digital signal, and processed using a computer. The twin measuring principle reduces the baseline noise and eliminates small temperature fluctuations in the thermostat. Isothermal Calvet calorimeters, operating in a batch mode, have been used to measure the enthalpies of mixing of ionic liquids and of their mixtures with water, with nitromethane, and with several alcohols. Special designs were adopted by different research groups in order to facilitate the mixing process of the 6080

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Figure 4. Schematic representation of an isothermal titration calorimeter.

when mixing two fluids. In this method, the heat involved in the addition of small quantity of one component to another is detected, providing a direct measurement of the partial molar excess enthalpy of the added component, the integration of the heat of solution being unnecessary.65 The high precision of the used calorimeters and of the titration units enables the use of very small quantities of the compounds, a few milliliters to fill the cell and up to 250 μL to fill the syringe, and allows the accurate measurement of the heat effects as long as sufficient time is allowed between additions to guarantee complete mixing. The differential evaporation of the components of the mixture that have very different volatilities constitutes a source of error that can be avoided by reducing the free volume in the measuring cell. The partial molar excess enthalpies of various organic solutes in ionic liquids have been measured using three different models of isothermal titration calorimeters: 2277 Thermal Activity Monitor TAM (Thermometrics),44,46−48 Thermal Activity Monitor TAM III (TA Instruments),45,50 and IMC 4400,49 (Calorimetry Sciences Corporation) with a refrigerating/heating circulator (9000, PolyScience Inc.). All these titration calorimeters are based on a twin configuration (one reference cell and one containing the sample) housed either in a water,44,47−49 or oil45,50 liquid thermostat, as presented in Figure 4. The thermostat temperature is very stable and is controlled to within 1 mK or better, resulting in high sensitivity. The detection is based on the heat flow principle, and the calorimeters operate in power compensation mode, which results in fast response times. The reported experiments using the isothermal titration calorimeters were performed following a similar protocol.44−51,73 First, a chemical calibration is done by determining the binding enthalpy of aqueous BaCl2 to 18-crown-6 ether44−48 or by measuring the partial excess enthalpies at infinite dilution of 1propanol + water, ethanol + water, or ethanol + 1-heptane.49,51,73 Additionally, an electrical calibration is usually done before each experiment. Typically, 3−8 μL of solute are added to 1−4 mL of solvent,44−48,50,51 but whenever necessary, higher quantities can be used up to 15.0 μL and 50 mL,49 respectively. The area of the observed peaks in each injection of the solute allows the determination of Qi per Δni and so of the partial excess enthalpy that can be calculated according to eq 2344−48,50,51

Other differential scanning calorimeters (model micro-DSC VII, Setaram, with a sensitivity of ±0.4 μW)21 under isothermal conditions and equipped with batch mixing cells have been used, the major source of uncertainty being, in this case, the spurious heat effects generated by stirring the high-viscosity mixtures. Undesirable heat effects and changes in the composition of the mixtures due to evaporation23,25,66 can be avoided by using flowmixing cells instead of batch ones. In flow mixing calorimeters, also based on the Calvet conduction principle, two fluids flow continuously in two branches of a Y-shaped metal tube and are mixed in a third branch, usually designated as mixing chamber (Figure 3a).65 The change in enthalpy resulting from the mixing process is measured under steady state conditions at constant pressure, flow rate, and known composition. The calorimetric signal is a difference in heat flow between the measuring (flow) and reference (batch) vessels. The vessels are usually placed in a metallic block, which is immersed in a thermostatic bath (water, silicone oil,41 or undecane22) and placed into an inert atmosphere. A Peltier cooler and several pulsed heaters, used to control the temperature, are placed inside the calorimetric block. Other elements of the flow mixing calorimeter include two high-precision liquid-pump systems (Figure 3, panels b−d), the thermal feedback circuit, a back pressure regulator (to avoid evaporation effects), and a vacuum/cleaning line (Figure 3a). Different flow calorimeters were used to determine the mixing enthalpies of ionic liquids,36−41 ionic liquids with water,34−42 2,2,2-trifluoroethanol,22 or carbon dioxide70 with uncertainties of around 1%, depending on the apparatus used (Hart Scientific model 7501, Micro DSC II or III calorimeters Setaram, model 2277 from LKB,71 and model C-80 from Setaram). 3.2. Partial Molar Excess Enthalpy

Flow-mix calorimeters have been widely used to measure the excess enthalpy of mixing even if a number of experiments at different flow ratios have to be carried out. The main limitations of this technique are linked with the difficulty of mixing two components with very different densities or viscosities, with the detection of very small heat effects when the two components are only partially miscible and with the need of relatively large amounts of the compounds to be studied. As an alternative, isothermal titration calorimetry (Figure 4)72 can be used to directly assess the partial molar excess enthalpies 6081

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H̅ iE ≈

Review

Qi Δni

(23)

where Qi is the heat effect involved in the injection of a small quantity Δni of solute to a solvent. The uncertainty on the partial excess molar enthalpy was estimated to be 2%.45,46

4. ENTHALPIES OF MIXING AND PARTIAL MOLAR EXCESS ENTHALPIES The enthalpy of mixing of systems involving ionic liquids has been measured using batch conduction calorimetry,21,23−33 flow mixing calorimetry,22,34,36−42 or adiabatic solution calorimetry.19,20,43 Measurements were performed in a relatively large concentration range, depending on the mutual solubility of the two compounds. Adiabatic or isoperibol solution calorimeters have been used to investigate the energetics of mixing close to infinite dilution,18,53−63 allowing the determination of the enthalpy of solution, usually expressed as a function of the amount of solute. Partial molar excess enthalpies, H̅ iE have been directly assessed by isothermal titration calorimetry, the enthalpy of mixing, ΔmixH, being calculated using the approach explained above.44−50 The correlation of the enthalpies of mixing obtained experimentally is done, as a function of composition, by a Redlich−Kister equation,21−26,29,31−34,41 as it is usually done to represent experimental data on thermodynamic excess properties.74 Some authors have also used semitheoretical activity coefficient models to correlate their data. Examples of such models are the UNIQUAC (UNIversal QUAsi Chemical75) approach,41 the modified UNIFAC (UNIversal Functional Activity Coefficient75) model with the Do76 correlation,36,40 the NRTL-Wilson77,78 model,19,20,41 or the ERAS (Extended version of the Real Associated Solution79).27,28 Some of these thermodynamic models, like ERAS or UNIFAC(Do), might be capable of predicting mixing enthalpies with accuracies on the order of 10%.38 Finally, COSMO (Conductor-like Screening Model80), namely the COSMO-RS (COSMO-Real Solvent) approach, has been recommended as a predictive method for calculating thermodynamic properties of mixtures involving ionic liquids.30 The data reported by Garcı ́a-Miaja et al.28 can be used as an example for the calculation of the mixing enthalpies for the ([C1C4Im][TfO] + CH3NO2) binary mixture reported at T = 303.15 K and p = 0.1 MPa. From the plots in Figure 5 (data in Table 1), which represent the behavior and the statistics of fitting the experimental data for ΔmixH to eq 10 with different number of parameters Ai, it is evident that four parameters were chosen for this case. This is further exemplified by using the data analysis of mixing enthalpies for ([C1C4Im][PF6] + ethanol) binary system at 288.15 K reported by Li et al.49 Although the authors recommended fitting the experimental ΔmixH data to Redlich− Kister equation of order three (RK3), herein only one parameter was used (RK1) due to the large error bars of the calculated partial molar excess enthalpies at infinite dilution for ethanol when three parameters were taken as original proposed by Li et al.49 The calculated values of H̅ 2E, ∞ were the following: (7.757 ± 0.027) kJ·mol−1 for RK1, (7.511 ± 5.035) kJ·mol−1 for RK2, and (7.580 ± 2197.5) kJ·mol−1 for RK3.

Figure 5. Dependence of the behavior of the calculated function representing ΔmixH on the number of parameters Ai used for fitting experimental data of mixing enthalpies to eq 10 for the system ([C1C4Im][TfO] + CH3NO2) reported at T = 303.15 K and p = 0.1 MPa by Garcı ́a-Miaja et al.28 Lines represent Redlich−Kister equation with different number of parameters Ai: RK1, dot-line; RK2, long dash line; RK3, short dash line; RK4, dash-dot line; and RK5, solid line. Subscript 2 refers to the molecular compound.

4.1. (Ionic Liquid + Ionic Liquid) Binary Mixtures

The enthalpies of mixing of 11 different (ionic liquid + ionic liquid) binary mixtures are reported in two different references of the open literature. Navia et al.31 measured the mixing enthalpies of two ionic liquids with a common anion, ([C1C2Im][BF4] + [C1C6Im][BF4]) and ([C1C4Im][BF4] + [C1C6Im][BF4]), and with a common cation, ([C1C4Im][BF4] + [C1C4Im][PF6]) and ([C 1C 4Im][BF4] + [C 1C4 Im][C 1SO 4]), over the whole composition range, at 303.15 K. In the work of Podgoršek et al.,50 the authors studied the effect of the length of alkyl chain in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and the effect of the nature of the cation and the anion on the interactions between ruthenium nanoparticles with ionic liquids. In order to get this information experimentally, the partial molar excess enthalpy of ([C1C4Im][NTf2] + [C1CnIm][NTf2]), ([C1C4Im][NTf2] + [C1C1C4Im][NTf2]), ([C1 C4 Im][NTf2] + [C 1C4 Pyrro][NTf2]), and ([C1C4Im][NTf2] + [C1C4Im][PF6]) were measured at the limiting sides of the composition range, as noted in Table 2.50 Experimental results, of ΔmixH from Navia et al.31 and of H̅ 2E and H1̅ E from Podgoršek et al.50 are plotted as a function of composition in Figure 6 (panels a and b), together with the fitted functions. For each system, Figure 6 presents also the calculated values for H̅ iE or ΔmixH and the calculated partial excess enthalpies at infinite dilution. The comparison of the enthalpies of mixing shows that for systems with a common anion, either BF4− or NTf2−, the values are positive over all the composition range, the results reported in both cases being consistent (0.065 kJ mol−1 for ([C1C6Im][BF4] + [C1C4Im][BF4])31 and 0.051 kJ mol−1 for ([C1C6Im][NTf2] + [C1C4Im][NTf2])50 at equimolar compositions). In the series of ionic liquids based on the C1CnIm+ cations, the enthalpy of mixing increases as the difference in the lengths of the alkyl chains increases, as can be seen by comparing the mixture ([C1C4Im][NTf2] + [C1C2Im][NTf2]) with ([C1C4Im][NTf2] + [C1C10Im][NTf2]). Surprisingly small values of ΔmixH for the ([C1C4Im][NTf2] + [C1C4Pyrro][NTf2]) and ([C1C4Im]6082

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Table 1. Statistics of Fitting Experimental Data ΔmixH for ([C1C4Im][TfO] + CH3NO2) at T = 303.15 K and p = 0.1 MPa Reported by Garcı ́a-Miaja et al.28 Using Eq 10 with Different Number of Parameters Ai, Units kJ mol−1a RKNb

A0

RK1

0.210 ± 0.035

RK2

0.212 ± 0.011

− 0.252 ± 0.030

RK3

0.255 ± 0.014

− 0.253 ± 0.028

− 0.092 ± 0.064

RK4

0.225 ± 0.007

− 0.151 ± 0.028

− 0.097 ± 0.033

− 0.312 ± 0.075

RK5

0.223 ± 0.009

− 0.152 ± 0.031

− 0.059 ± 0.102

− 0.312 ± 0.082

A1

A2

A3

A4

− 0.073 ± 0.182

R2

σΔmixHc

RAADd

0.8184

0.006

27.82

0.9841

0.003

8.82

0.9881

0.004

9.78

0.9973

0.003

4.11

0.9974

0.006

3.49

H1̅ E, ∞

0.210 ± 0.035 0.464 ± 0.032 0.386 ± 0.071 0.591 ± 0.087 0.555 ± 0.227

H̅ 2E, ∞ 0.210 ± 0.035 −0.040 ± 0.032 −0.120 ± 0.071 −0.336 ± 0.087 −0.373 ± 0.227

In this example, ΔmixH data were fitted with the respect if the compound mole fraction. bNumber of parameters in Redlich−Kister equation (eq 10). cStandard deviations. dIn percent.

a

Table 2. Molar Enthalpy of Mixing, ΔmixH at Equimolar Composition, and Calculated Partial Molar Excess Enthalpies at Infinite Dilution, H̅ iE, ∞ of (Ionic Liquid + Ionic Liquid) Binary Mixtures at p = 0.1 MPa Reported in the Literaturea system (1 + 2)

T (K)

x1 range

data

ΔmixH(kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

apparatus

reference

[C1C2Im][BF4] + [C1C6Im][BF4] [C1C4Im][BF4] + [C1C4Im][PF6] [C1C4Im][BF4] + [C1C6Im][BF4] [C1C4Im][BF4] + [C1C4Im][C1SO4] [C1C4Im][NTf2] + [C1C2Im][NTf2] [C1C4Im][NTf2] + [C1C6Im][NTf2] [C1C4Im][NTf2] + [C1C8Im][NTf2] [C1C4Im][NTf2] + [C1C10Im][NTf2] [C1C4Im][NTf2] + [C1C4Im][PF6] [C1C4Im][NTf2] + [C1C1C4Im][NTf2] [C1C4Im][NTf2] + [C1C4Pyrro][NTf2]

303.15 303.15 303.15 303.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15

[0−1] [0−1] [0−1] [0−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1] [0−0.3; 0.7−1]

11 9 9 10 105 100 103 105 105 89 106

0.285 ± 0.009 − 0.116 ± 0.006 0.065 ± 0.003 − 0.339 ± 0.009 0.058 ± 0.001 0.051 ± 0.001 0.182 ± 0.003 0.359 ± 0.005 0.414 ± 0.021 0.013 ± 0.001 0.004 ± 0.000

0.893 ± 0.107 − 0.566 ± 0.087 0.202 ± 0.034 − 1.303 ± 0.111 0.262 ± 0.018 0.188 ± 0.006 0.588 ± 0.013 1.058 ± 0.028 1.955 ± 0.275 0.060 ± 0.011 0.001 ± 0.002

1.383 ± 0.107 − 0.358 ± 0.087 0.318 ± 0.034 − 1.406 ± 0.111 0.196 ± 0.007 0.212 ± 0.009 0.956 ± 0.044 1.952 ± 0.078 1.533 ± 0.027 0.071 ± 0.006 0.035 ± 0.001

Calvet Calvet Calvet Calvet ITC ITC ITC ITC ITC ITC ITC

31 31 31 31 50 50 50 50 50 50 50

Values of ΔmixH and H̅ iE, ∞ reported in italics were obtained by extrapolation of the calculated data out of the experimentally studied composition range. Subscripts 1 and 2 indicate the first and the second ionic liquids, respectively.

a

Figure 6. Calorimetric properties of (ionic liquid + ionic liquid) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞, for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ◆, ([C1C2Im][BF4] + [C1C6Im][BF4]); ▼, ([C1C4Im][BF4] + [C1C6Im][BF4]); ●, ([C1C4Im][BF4] + [C1C4Im][PF6]); ■, ([C1C4Im][BF4] + [C1C4Im][C1SO4]), using reported data for ΔmixH at T = 303.15 K from Navia et al.,31 and for ○, ([C1C4Im][NTf2] + [C1C2Im][NTf2]); □, ([C1C4Im][NTf2] + [C1C6Im][NTf2); △, ([C1C4Im][NTf2] + [C1C8Im][NTf2); ◇, ([C1C4Im][NTf2] + [C1C10Im][NTf2]); ▽, ([C1C4Im][NTf2] + [C1C1C4Im][NTf2]); ⬡, ([C1C4Im][NTf2] + [C1C4Pyrro][NTf2]); ▼, ([C1C4Im][NTf2] + [C1C4Im][PF6]), using reported data for H̅ iE at T = 298.15 K from Podgoršek et al.50 The lines represent data fittings using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

[NTf2] + [C1C4Im][PF6]) mixtures seem to indicate that mixing these ionic liquids does not affect significantly the molecular

interactions in the mixture. Mixing [C1C4Im][PF6] and [C1C4Im][NTf2] is an endothermic process as a ΔmixH of 6083

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Figure 7. Calorimetric properties of (ionic liquid + water) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ●, ([C1C4Im][BF4] + water) at T = 298.15 K;34 ▲, ([b2mPy][BF4] + water) at T = 298.15 K;30 △, ([b3mPy][BF4] + water) at T = 298.15 K;32 ▼, ([b4mPy][BF4] + water) at T = 298.15 K;33 ■, ([N2000][NO3] + water) at 298.15 K;42 □, ([N3000][NO3] + water) at 298.15 K;42 ◆, ([C1C2Im][TfO] + water) at T = 313.15 K;25 ◇, ([C1C4Im][TfO] + water) at T = 303.15 K;26 +, ([C1C6Im][TfO] + water) at T = 313.15 K;24 and ⬢, ([C1C2Im][SCN] + water) at T = 313.15 K.24 The lines represent data fittings using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems, ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 8. Calorimetric properties of (ionic liquid + water) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞, for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ●, ([P2224][DEP] + water) at T = 313.15 K;24 ○, ([C1C2Im][DEP] + water) at T = 313.15 K;24 ▲, ([Chol][Lac] + water) at T = 313.15 K;21 △, ([Chol][Glyc] + water) at T = 313.15 K;21 +, ([C1C2Im][CF3CO2] + water) at T = 313.04 K;25 ■, ([C1C2Im][C1SO3] + water) at T = 313.14 K;23 □, ([C1C2Im][HSO4] + water) at T = 313.14 K;23 ◆, ([C1C2Im][C1SO4] + water) at T = 313.14 K;23 ◇, ([C1C2Im][C2SO4] + water) at T = 313.14 K;23 ⬣, ([C1C4Im][C1SO4] + water) at T = 303.15 K;26 ▼, ([C1C1Im][DMP] + water) at T = 298.15 K;19 and ▽, ([C1C2Im][DMP] + water) at T = 298.15 K.20 The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems, ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

around +0.4 kJ mol−1 was calculated.50 This result shows that the

The same conclusions can be drawn by examining partial enthalpies at infinite dilution, H1̅ E, ∞ and H̅ 2E, ∞. In each case, the difference between these two quantities increases when the difference of the alkyl side-chain length of the cation increases, becoming important for Δn ≥ 4. In the series of C1CnIm+-based ionic liquids, the values of H̅ iE, ∞ are always higher for the ionic

31

general conclusions of Navia et al., who state that interactions between unlike anions are more favorable than between like ones, cannot be generalized for other ionic liquids mixtures, even when they seem relatively similar. 6084

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Figure 9. Partial molar excess enthalpies at infinite dilution, H1̅ E, ∞, of ionic liquids in water at T = 298.15 K and p = 0.1 MPa, consistency of calculated values for the [C1CnIm][BF4] and overview of Yang data for [C1CnIm]Cl: (a) IL = [C1CnIm][BF4] from ●63, ○62, dark gray ●34, gray ○18, and ○56 and (b) IL = [C1CnIm]Cl from n = 2,62 n = 4,59 n = 5,61 and n = 6.53

ionic liquids based on the BF4− anion, independent of the cation studied. In Figure 8 are represented the enthalpies of mixing of (ionic liquids + water) mixtures that present negative values of ΔmixH. The ionic liquids represented are based on the Cl−, the HSO4−, the CnSO4− (n = 1 or 2), the C1SO3−, the CF3CO2−, the Glyc−, the DEP−, the Lac−, and the DMP− anions associated with short alkyl side-chain imidazolium, phosphonium, and cholinium cations. The most negative mixing enthalpy has been reported for the mixture ([Chol][Lac] + water)21 followed by the mixtures with water of ionic liquids based on the DEP− anion (imidazolium cations making the enthalpy of mixing more negative than phosphonium cations24), the Glyc− anion,21 and the CF3CO2− anion.25 For this group of ionic liquids, the partial molar excess enthalpies at infinite dilution vary 2 orders of magnitude, depending on the ionic liquids, being as low as −200 kJ mol−1 for [Chol][Lac] in water and less than −10 kJ mol−1 for [C1C4Im][C1SO4] in water. The comparison between the partial molar enthalpies when the ionic liquid is added to pure water or when water is added to the pure ionic liquid is represented in Figure 8d. Because the binary mixtures ([C1CnIm][BF4] + water) and ([C1CnIm]Cl + water) were studied by several research groups using different experimental techniques, it was possible to analyze the consistency of the experimental data and the trends of the energetic properties of mixing. The values of ΔmixH and H1̅ E, ∞ are positive for [C1CnIm][BF4] and negative for [C1CnIm] Cl and do not vary monotonously with the number of carbon atoms in the alkyl side-chain of the cation. Figure 9a shows acceptable agreement between the calculated values for the limiting partial excess enthalpy for [C1C2Im][BF4] calculated from the experimentally measured values of ΔsolH of the ionic liquid in water reported by two different authors, Waliszewski et al.63 and Yang et al.,62 the values from Guan et al.56 deviating more significantly. For ([C1C4Im][BF4] + water), a good consistency is observed even if the values have been calculated either from ΔsolH or ΔmixH assessed by different calorimetric methods (isoperibolic56,63 or adiabatic solution calorimetry18 and Calvet flow-mix calorimetry34). Figure 9b shows the calculated values for H1̅ E, ∞ in mixtures of ([C1CnIm]Cl + water) obtained from experimentally measured ΔsolH. The mixing process of [C1CnIm]Cl with water is exothermic and the H1̅ E, ∞ values increase with the size of the alkyl side-chain in the cation from 2 to 4 carbon atoms and then

liquid with larger number of carbon atoms in the alkyl chain, probably due to the importance of van der Waals interactions between cations with longer alkyl chain. As expected, it is easier to dissolve the ionic liquid with the shorter alkyl chain in the ionic liquid with the larger chain than the other way around. In accordance with the values of H1̅ E, ∞ for the systems with C1C4Im+, we can see that the interactions in pure [C1C4Im][BF4] are weaker than in pure [C1C4Im][PF6] and the interactions in pure [C1C4Im][PF6] are weaker than in pure [C1C4Im][NTf2]. Analogous observation suggests that the strength of the interactions in pure [C1C4Im][BF4] and [C1C4Im][C1SO4] are similar, since both values of H̅ iE, ∞ are the same within the respective error bars. The fact that the values of the partial excess enthalpies at infinite dilution for ([C1C1C4Im][NTf2] + [C1C4Im][NTf2]) and ([C1C4Pyrro][NTf2] + [C1C4Im][NTf2]) are much smaller in comparison with ([C1CnIm][NTf2] + [C1C4Im][NTf2]) indicates that the change in the electrostatic interactions (including hydrogen bonds) between different ionic liquids with a common anion plays a minor role in comparison with the dispersive forces. 4.2. (Ionic Liquid + Associating Compound) Binary Mixtures

In Figures 7 and 8 are plotted the experimentally determined values of the mixing enthalpies for various ionic liquids with water. It can be observed in Figure 7 that the mixing enthalpies with water are positive in the whole composition range for ionic liquids with the BF4−,30,32−34 NO3−42 (Figure 7a, upper plot), or TfO−24−26 anions (Figure 7a, lower plot) when associated with imidazolium, pyridinium, or ammonium cations. Only one ionic liquid based on the SCN− anion was studied, the ([C1C2Im][SCN] + water) mixture showing a S-shape dependence of ΔmixH with composition at 313.15 K with positive enthalpies of mixing for compositions poor in ionic liquid (Figure 7a, lower plot).24 The partial molar excess enthalpy for [C1C2Im][NTf2] in water at infinite dilution was determined to have also a positive value.63 The largest positive values of ΔmixH for the mixtures (ionic liquid + water) are found for ionic liquids based on the BF4− anion (imidazolium cations leading to larger enthalpies of mixing), followed by ionic liquids based on the TfO− anion and then those based on the NO3− anion. The partial molar excess enthalpies vary significantly, the general trend being that the values are more positive when the ionic liquid is added to pure water (Figure 7b) than when water is added to the pure ionic liquid (Figure 7c). H1̅ E, ∞ (Figure 7b) is more positive for the 6085

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Figure 10. Consistency of published calorimetric properties of the ([C1C2Im][C2SO4] + water) binary mixture at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH, as a function of composition and (b) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for △, Balantseva et al.,44 at T = 298.15 K; ▲, Leskiv et al.43 at T = 298.15 K; ■, Garcı ́a-Miaja et al.26 at T = 303.15 K; circle symbols, Ficke et al.25 at ●, T = 313.15 K; ○, 323.15 K; gray ●, 333.15 K; and gray ○, 348.15 K. The solid and dashed lines represent fitted data and extrapolated data using eq 10 for ΔmixH, respectively. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 11. Temperature effect on calorimetric properties of (ionic liquid + water) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH as a function of composition and temperature: filled symbols and solid lines for T = 313.15 K, open symbols and dashed lines for T = 333.15 K. (b) H̅ iE, ∞ for components in binary mixtures. Filled and open symbols correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ◇, ([C1C4Im][BF4] + water);34 □, ([C1C2Im][TfO] + water);25 ▽, ([C1C2Im][CF3CO2] + water);25 and ○, ([C1C2‑OHIm][CF3CO2] + water).23 The lines represent data fittings using eq 10 for ΔmixH. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 12. Effect of the alkyl-chain length of the alcohol CkH2k+1OH on calorimetric properties of (ionic liquid + CkH2k+1OH) binary systems at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH, at the equimolar composition and (b) H̅ 2E, ∞ for binary mixtures containing CkH2k+1OH and ■, [C1C2Im][NTf2] from Deng et al. at T = 298.15 K;46 gray ■, [C1C2Im][NTf2] from Nebig et al. at T = 323.15 K;36 □, [C1C6Im][NTf2] from Deng et al. at T = 298.15 K;46 ○, [C1C4Im][PF6] from Li et al. at T = 298.15 K;49 ●, [C1C2Im][C2SO4] from Balantseva et al. at T = 298.15 K;44 ▲, [b2mPy][BF4] data from Navas et al. at T = 318.15 K;30 △, [b3mPy][BF4] data from Ortega et al. at T = 318.15 K;32 ▽, [b4mPy][BF4] data from Ortega et al. at T = 318.15 K;33 and ◇, [N1114][NTf2] data from Balantseva et al. at T = 298.15 K.44 Subscript 2 refers to the molecular compound.

interaction of water with C1C4Im+ in the case of [C1C4Im][BF4] than in the case of [C1C4Im]Cl. Figure 10 addresses the consistency of the published calorimetric properties for the ([C1C2Im][C2SO4] + water) binary mixture. Balantseva et al.44 have reported partial excess

decreases for longer chains. Even if Guan et al. reported a positive and then a negative value for the partial molar excess enthalpy for [C1C4Im]Cl at infinite dilution (+5.440 ± 0.262 kJ mol−159 or −5.440 kJ mol−153), a nonmonotonous variation of H1̅ E, ∞ is observed and can probably be explained by a more favorable 6086

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Figure 13. Effect of the alkyl-chain length on the imidazolium cation, C1CnIm+ on calorimetric properties of (ionic liquid + CkH2k+1OH) binary systems at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH, at the equimolar composition and (b) H̅ 2E, ∞ for binary mixtures containing □, ([C1CnIm][NTf2] + methanol) from Deng et al. at T = 298.15 K;46 ■ ([C1CnIm][DMP] + methanol) from Zhao et al. at T = 298.15 K;19,20 ○, ([C1CnIm][NTf2] + ethanol) from Deng et al. at T = 298.15 K;46 gray ●, ([C1CnIm][TfO] + ethanol) from Garcı ́a-Miaja et al. at T = 303.15 K;27 ●, ([C1CnIm][DMP] + ethanol) from Zhao et al. at T = 298.15 K;19,20 ◇, ([C1CnIm][NTf2] + 1-butanol) from Deng et al. at T = 298.15 K;46 and △, ([C1CnIm][NTf2] + 1-hexanol) from Deng et al. at T = 298.15 K.46 Subscript 2 refers to the molecular compound.

[NTf2] (n = 2 to 10) + alcohol), the enthalpies of mixing (Figure 13a) and the partial molar excess enthalpies (Figure 13b) are positive and do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid, increasing from n = 2 to 6 and then decreasing from n = 8.46 Concerning the ionic liquids [C1CnIm][TfO], the values of ΔmixH (Table 3, Figure 13) are positive and slightly decrease with the increasing size of the alkyl side chain. Changing the anion of the ionic liquid does have an effect on the enthalpy of mixing with ethanol as can be seen for the reported values for [C1C2Im][TfO]27 and [C1C2Im][NTf2]46 for which the ΔmixH at equimolar composition does not differ significantly, the limiting partial molar excess enthalpies indicating, nevertheless, an energetically more favorable dissolution of ethanol in [C1C2Im][TfO] than in [C1C2Im][NTf2]. The temperature dependence on the heats of mixing for some of the (ionic liquid + alcohol) binary systems is represented in Figure 14. For ([b2mPy][BF4] + ethanol), Navas et al.30 reported that the mixing enthalpies become more positive with increasing temperature (Figure 14a). On the contrary, a decrease in ΔmixH with temperature was observed for two systems containing 1,1,1-trifluoroethanol, ([C 1 C 2 Im][BF 4 ] + CF3CH2OH), and ([C1C4Im][BF4] + CF3CH2OH).22 The partial molar enthalpies at infinite dilution of (ionic liquid + alcohol) binary mixtures are represented in Figure 14b as a function of temperature. The positive values of H̅ iE, ∞ are larger for the ionic liquid than for the alcohol for all the systems studied. A detailed analysis of the behavior at different temperatures (at 298.15 and 318.15 or 323.15 K) showed that, depending on the system, an increase [for ([b4mPy][BF4 ] + ethanol), 33 ([b3mPy][BF4] + ethanol)32] or a decrease [for ([C1C2Im][BF4] + CF3CH2OH),22 ([C1C4Im][BF4] + CF3CH2OH)22] in H̅ iE, ∞ was observed, with the most striking change being observed for the ([C1 C 4 Im][BF4 ] + CF3 CH 2OH) and ([b4mPy][BF4] + ethanol) systems. Li et al.49 reported that the values of the limiting partial molar excess enthalpy do not change remarkably with temperature for the ([C1C4Im][PF6] + 2-propanol) mixture. In Figure 15 are represented the enthalpies of mixing of (ionic liquid + methanol) binary mixtures at 0.1 MPa and 298.15 K. It can be seen that for [C1C1Im][DMP]19 and [C1C2Im][DMP],20 the values of the mixing enthalpies are negative, whereas for

molar enthalpies of water in [C1C2Im][C2SO4] at 298.15 K measured by isothermal titration calorimetry in a very narrow concentration range (that is the reason why for this series only the partial molar excess enthalpy at infinite dilution of water was calculated). Values of ΔmixH determined by isoperibol solution calorimetry by Leskiv et al.43 or by Calvet microcalorimeter by Garcı ́a-Miaja et al.26 agree to within their mutual uncertainties, the slight discrepancies being attributed to the different temperatures of the measurements (and 298.15 and 303.15 K) since it was observed25 that an increase in the temperature slightly disfavors the mixing process. The temperature dependence of the enthalpies of mixing for various ionic liquids with water is illustrated in Figure 11. The enthalpy of mixing is positive for ([C1C4Im][BF4] + water) and increases with increasing temperature,41 while for ([C1C2Im][CF3CO2] + water) it is negative and increases with increasing temperature24 from 313.15 to 333.15 K. In Figure 11b, it can be observed that the temperature has a larger effect on H̅ iE, ∞ for the ionic liquid in water than on H̅ iE, ∞ for water in the ionic liquid. Because mixtures of alcohols with ionic liquids have been extensively studied, it is possible to check the effect of the molecular structure of the alcohol or of the ionic liquid on the enthalpies of mixing in their mixtures. The effect of the alkylchain length of the alcohol CkH2k+1OH on the calorimetric properties of various (ionic liquid + CkH2k+1OH) binary systems is illustrated in Figure 12, enthalpies of mixing, ΔmixH, at equimolar composition in Figure 12a) and limiting partial excess molar enthalpies of alcohol, H̅ 2E, ∞, in Figure 12b). For the seven ionic liquids considered, based on imidazolium, pyridinium, and ammonium cations, the values of ΔmixH and H̅ 2E, ∞ are positive and increase monotonously with the number of carbon atoms in alcohol up to k = 4, and then for k > 4 they become constant, or slightly decrease. The effect of the size of the alkyl-chain in the imidazolium cation on calorimetric properties of (ionic liquid + CkH2k+1OH) binary systems, reported for three different families of 1-alkyl-3methylimidazolium ionic liquids, [C1CnIm][NTf2], [C1CnIm][DMP], and [C1CnIm][TfO], is represented in Figure 13. It is observed that the values of ΔmixH and H̅ 2E, ∞ are positive for the ionic liquids based on the NTf2− and the TfO− anions but are negative for the mixtures of methanol and ethanol with [C1CnIm][DMP] ionic liquids.19,20 For the mixtures ([C1CnIm]6087

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Table 3. Molar Enthalpy of Mixing, ΔmixH at Equimolar Composition, and Calculated Partial Molar Excess Enthalpies at Infinite Dilution, H̅ iE, ∞ of (Ionic Liquid + Associative Compound) Binary Mixtures at p = 0.1 MPa Reported in the Literaturea system (1 + 2) [C1C2Im][NTf2] + water [C1C2Im][NTf2] + methanol [C1C2Im][NTf2] + methanol [C1C2Im][NTf2] + methanol [C1C2Im][NTf2] + ethanol [C1C2Im][NTf2] + ethanol [C1C2Im][NTf2] + 1propanol [C1C2Im][NTf2] + 1butanol [C1C2Im][NTf2] + tbutanol [C1C2Im][NTf2] + 1hexanol [C1C2Im][NTf2] + 1hexanol [C1C2Im][NTf2] + 1,2ethanediol [HOC2C1Im][NTf2] + ethanolamine [C1C4Im][NTf2] + methanol [C1C6Im][NTf2] + methanol [C1C6Im][NTf2] + methanol [C1C6Im][NTf2] + ethanol [C1C6Im][NTf2] + ethanol [C1C6Im][NTf2] + 1butanol [C1C6Im][NTf2] + 1butanol [C1C6Im][NTf2] + 1hexanol [C1C6Im][NTf2] + 1hexanol [C1C6Im][NTf2] + ethanolamine [C1C8Im][NTf2] + methanol [C1C10Im][NTf2] + methanol [C1C2Im][BF4] + water [C1C2Im][BF4] + water [C1C2Im][BF4] + water [C1C2Im][BF4] + methanol [C1C2Im][BF4] + methanol [C1C2Im][BF4] + 1,2ethanediol [C1C2Im][BF4] + formamide [C1C2Im][BF4] + CF3CH2OH [C1C2Im][BF4] + CF3CH2OH [C1C2Im][BF4] + 2pyrrolidone [C1C4Im][BF4] + water [C1C4Im][BF4] + water

T (K)

x1 range

data

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

apparatus

reference

298.15

nc

nc

+

7.810 ± 0.470

nc

Isoperibol

63

298.15

[0.9−1]

21

1.437 ± 0.007

nc

5.749 ± 0.030

ITC

48

298.15

[0.85−1]

15

1.344 ± 0.030

nc

5.740 ± 0.204

ITC

46

b

298.15

nc

nc

+

13.730 ± 0.310

nc

Isoperibol

63

298.15

[0.88−1]

15

1.813 ± 0.002

nc

7.251 ± 0.007

ITC

46

323.15

[0−1]

8

2.414 ± 0.020

13.447 ± 0.333

7.421 ± 0.333

IFC

36

323.15

[0−1]

8

2.675 ± 0.030

15.126 ± 0.504

8.245 ± 0.504

IFC

36

298.15

[0.92−1]

15

1.856 ± 0.023

nc

8.518 ± 0.141

ITC

46

298.15

[0.91−1]

22

1.240 ± 0.040

nc

6.943 ± 0.249

ITC

48

298.15

[0.97−1]

11

+

nc

8.572 ± 13.373

ITC

48

298.15

[0.97−1]

7

+

nc

7.706 ± 12.380

ITC

46

298.15

[0.89−1]

17

−1.256 ± 0.352

nc

4.900 ± 2.312

ITC

48

313.15

[0−1]

15

−1.981 ± 0.021

−6.473 ± 0.445

−9.128 ± 0.445

Calvet

98

298.15

[0.83−1]

15

1.589 ± 0.008

nc

7.069 ± 0.054

ITC

46

298.15

[0.82−1]

16

2.116 ± 0.014

nc

7.383 ± 0.106

ITC

47

298.15

[0.81−1]

15

2.270 ± 0.014

nc

7.367 ± 0.103

ITC

46

298.15

[0.87−1]

15

2.244 ± 0.008

nc

8.620 ± 0.050

ITC

46

353.15

[0−1]

8

2.231 ± 0.010

12.751 ± 0.168

5.606 ± 0.168

IFC

36

298.15

[0.91−1]

21

2.748 ± 0.013

nc

9.310 ± 0.080

ITC

47

298.15

[0.91−1]

15

2.585 ± 0.020

nc

9.201 ± 0.125

ITC

46

298.15

[0.89−1]

12

1.851 ± 0.063

nc

9.104 ± 0.405

ITC

47

298.15

[0.93−1]

15

1.675 ± 0.038

nc

9.074 ± 0.232

ITC

46

313.15

[0−1]

16

2.340 ± 0.007

11.619 ± 0.134

13.344 ± 0.134

Calvet

98

298.15

[0.81−1]

15

1.967 ± 0.035

nc

6.034 ± 0.499

ITC

46

298.15

[0.79−1]

15

0.875 ± 0.034

nc

3.959 ± 0.518

ITC

46

298.15 298.15 298.15 298.15

nc [0−0.002] [0−0.33] nc

nc 11 9 nc

+ + 0.087 ± 0.010 +

17.330b ± 0.270 18.311 ± 0.683 0.795 ± 0.229 19.020b ± 0.130

nc nc nc nc

Isoperibol Isoperibol ITC Isoperibol

63 62 51 63

298.15

[0−0.38]

9

0.231 ± 0.021

2.641 ± 0.545

nc

ITC

51

298.15

[0.26−0.65]

9

0.313 ± 0.001

1.837 ± 0.007

nc

ITC

51

298.15

[0−0.58]

10

0.186 ± 0.004

1.658 ± 0.081

nc

ITC

51

298.15

[0−1]

10

1.040 ± 0.025

8.344 ± 0.506

2.153 ± 0.506

Calvet

22

323.15

[0−1]

11

0.648 ± 0.024

5.538 ± 0.478

1.054 ± 0.478

Calvet

22

298.15

[0−1]

18

−0.315 ± 0.001

−1.138 ± 0.013

−0.886 ± 0.013

Calvet

83

278.15 283.15

[0−0.059; 0.175−1] [0−1]

7 9

1.879 ± 0.034 1.889 ± 0.026

13.535 ± 0.803 14.042 ± 0.547

5.172 ± 0.803 5.204 ± 0.547

Calvet Calvet

34 34

b

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Table 3. continued system (1 + 2)

T (K)

x1 range

data

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

[C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4]

+ + + + + +

water water water water water water

288.15 293.15 298.15 298.15 298.15 298.15

[0−1] [0−1] [0−1] [0−0.0003] nc nc

9 9 9 2 nc nc

1.899 ± 0.026 1.908 ± 0.026 1.918 ± 0.026 + + +

14.531 ± 0.544 15.006 ± 0.538 15.477 ± 0.542 15.234 ± 0.094 15.810b ± 0.310 15.740b ± 0.510

5.226 ± 0.544 5.233 ± 0.538 5.247 ± 0.542 nc nc nc

[C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] [C1C4Im][BF4] methanol [C1C4Im][BF4] methanol [C1C4Im][BF4] ethanol [C1C4Im][BF4] ethanol [C1C4Im][BF4] ethanol [C1C4Im][BF4] propanol [C1C4Im][BF4] propanol [C1C4Im][BF4] propanol [C1C4Im][BF4] ethanediol [C1C4Im][BF4] ethanediol [C1C4Im][BF4] formamide [C1C4Im][BF4] formamide [C1C4Im][BF4] CF3CH2OH [C1C4Im][BF4] CF3CH2OH [C1C6Im][BF4] [C1C6Im][BF4] methanol [C1C6Im][BF4] ethanol [C1C6Im][BF4] ethanol [C1C6Im][BF4] propanol [C1C6Im][BF4] ethanediol [C1C6Im][BF4] formamide [C1C8Im][BF4] [C1C8Im][BF4] [C1C8Im][BF4] [C1C8Im][BF4] [C1C8Im][BF4] methanol [C1C8Im][BF4] ethanol [C1C8Im][BF4] propanol [C1C8Im][BF4] ethanediol [C1C8Im][BF4] formamide

+ + + + + + + +

water water water water water water D2O

298.15 298.15 303.15 313.15 323.15 333.15 298.15 298.15

[0−0.003] [0−0.48] [0−1] [0−1] [0−1] [0−1] [0−0.53] nc

16 19 9 9 9 9 17 nc

+ 0.029 1.927 1.945 1.962 1.978 0.033 +

17.485 ± 0.559 0.304 ± 0.031 15.951 ± 0.550 16.921 ± 0.576 17.934 ± 0.622 19.009 ± 0.692 0.377 ± 0.037 18.500b ± 0.220

nc nc 5.254 5.294 5.369 5.502 nc nc

+

298.15

[0−0.68]

26

0.189 ± 0.006

1.831 ± 0.086

+

298.15

[0−0.74]

24

0.385 ± 0.008

+

303.15

[0−1]

12

+

298.15

nc

+ 1-

298.15

+ 1+ 2-

apparatus

reference

Calvet Calvet Calvet Adiabatic Isoperibol Differential calorimeter Isoperibol ITC Calvet Calvet Calvet Calvet ITC Isoperibol

56 51 34 34 34 34 51 63

nc

ITC

51

3.341 ± 0.108

nc

ITC

51

2.470 ± 0.027

15.516 ± 0.565

8.411 ± 0.565

Calvet

29

nc

+

24.520b ± 0.310

nc

90

[0−0.75]

24

0.509 ± 0.009

4.241 ± 0.123

nc

Differential calorimeter ITC

298.15

nc

nc

+

26.990b ± 0.320

nc

298.15

nc

nc

+

26.410b ± 0.530

nc

b

± ± ± ± ± ±

0.001 0.026 0.027 0.030 0.033 0.002

± ± ± ±

0.550 0.576 0.622 0.692

34 34 34 18 63 90

51

+ 1,2-

298.15

nc

nc

+

16.280 ± 0.200

nc

+ 1,2-

298.15

[0.13−0.79]

24

0.284 ± 0.003

2.013 ± 0.034

nc

Differential calorimeter Differential calorimeter Differential calorimeter ITC

90

+

298.15

[0−0.52]

9

0.153 ± 0.004

1.421 ± 0.096

nc

ITC

51 90 22

90 90 51

+

298.15

nc

nc

+

6.950 ± 0.170

nc

+

298.15

[0−1]

13

1.013 ± 0.014

11.383 ± 0.280

2.606 ± 0.280

Differential calorimeter Calvet

+

323.15

[0−1]

11

0.588 ± 0.013

5.824 ± 0.268

0.986 ± 0.268

Calvet

22

+ water +

298.15 298.15

[0−0.29] [0−0.36]

14 14

−0.111 ± 0.027 0.056 ± 0.005

−0.741 ± 0.508 0.574 ± 0.116

nc nc

ITC ITC

51 51

+

298.15

[0−0.45]

13

0.047 ± 0.000

0.304 ± 0.007

nc

ITC

51

+

303.15

[0−1]

9

2.459 ± 0.023

15.436 ± 0.467

7.576 ± 0.467

Calvet

27

+ 1-

298.15

[0−0.52]

14

−0.168 ± 0.010

−2.614 ± 0.229

nc

ITC

51

+ 1,2-

298.15

[0.17−0.60]

13

0.029 ± 0.000

0.138 ± 0.003

nc

ITC

51

+

298.15

[0−0.53]

14

0.110 ± 0.004

1.183 ± 0.100

nc

ITC

51

298.15 298.15 306.15 313.15 298.15

[0−0.0004] [0−0.11] nc [0−0.0003] [0−0.14]

8 14 1 9 14

+ −1.007 ± 0.155 + + −1.550 ± 0.400

19.320 ± 0.089 −0.592 ± 1.825 22.090b ± 0.150 24.813 ± 0.107 −1.429 ± 5.114

nc nc nc nc nc

Adiabatic ITC Adiabatic Adiabatic ITC

18 51 18 18 51

+

298.15

[0−0.20]

14

−3.469 ± 0.835

−8.524 ± 12.299

nc

ITC

51

+ 1-

298.15

[0−0.25]

14

−0.966 ± 0.250

−4.198 ± 4.190

nc

ITC

51

+ 1,2-

298.15

[0−0.31]

14

−0.054 ± 0.013

−0.468 ± 0.266

nc

ITC

51

+

298.15

[0−0.26]

14

0.087 ± 0.020

0.444 ± 0.348

nc

ITC

51

+ + + + +

water water water water

b

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Table 3. continued data

ΔmixH (kJ mol−1)

[0−0.002] [0−0.002] [0−0.002] [0−0.002] [0−1]

11 18 16 18 5

− + − − −5.868 ± 0.217

−5.824 ± 0.241 5.440 ± 0.262 −6.409 ± 0.089 −8.663 ± 0.592 −59.105 ± 9.384

nc nc nc nc −42.177 ± 9.384

Isoperibol Isoperibol Isoperibol Isoperibol Adiabatic

62 59 61 53 19

298.15

[0−1]

5

−3.248 ± 0.084

−19.145 ± 2.060

−7.772 ± 2.060

Adiabatic

19

298.15

[0−1]

5

−2.076 ± 0.040

−10.026 ± 0.844

−4.231 ± 0.844

Adiabatic

19

298.15

[0−1]

5

−5.830 ± 0.134

−44.941 ± 2.843

−17.609 ± 2.843

Adiabatic

20

298.15

[0−1]

5

−3.341 ± 0.085

−19.711 ± 1.846

−8.889 ± 1.846

Adiabatic

20

298.15

[0−1]

5

−2.437 ± 0.107

−17.571 ± 2.408

−6.851 ± 2.408

Adiabatic

20

288.15

[0.99−1]

8

1.939 ± 0.007

nc

7.757 ± 0.027

ITC

49

298.15

[0.99−1]

8

1.778 ± 0.009

nc

7.113 ± 0.035

ITC

49

308.15

[0.99−1]

8

1.867 ± 0.018

nc

7.469 ± 0.070

ITC

49

318.15

[0.99−1]

8

2.025 ± 0.018

nc

8.099 ± 0.071

ITC

49

288.15

[0.992−1]

8

2.263 ± 0.006

nc

9.052 ± 0.024

ITC

49

298.15

[0.992−1]

8

2.287 ± 0.015

nc

9.148 ± 0.061

ITC

49

308.15

[0.992−1]

8

2.263 ± 0.010

nc

9.051 ± 0.041

ITC

49

318.15

[0.99−1]

8

2.525 ± 0.005

nc

10.099 ± 0.022

ITC

49

288.15

[0.992−1]

8

2.356 ± 0.004

nc

9.425 ± 0.017

ITC

49

298.15

[0.992−1]

8

2.358 ± 0.003

nc

9.434 ± 0.011

ITC

49

308.15

[0.992−1]

8

2.199 ± 0.022

nc

8.797 ± 0.087

ITC

49

318.15

[0.992−1]

8

2.318 ± 0.018

nc

9.271 ± 0.071

ITC

49

288.15

[0.993−1]

8

2.580 ± 0.004

nc

10.321 ± 0.016

ITC

49

298.15

[0.993−1]

8

2.707 ± 0.013

nc

10.827 ± 0.050

ITC

49

308.15

[0.993−1]

8

2.508 ± 0.010

nc

10.033 ± 0.040

ITC

49

318.15

[0.993−1]

8

2.709 ± 0.017

nc

10.836 ± 0.069

ITC

49

328.15

[0.993−1]

8

3.022 ± 0.012

nc

12.089 ± 0.050

ITC

49

303.15 313.14 323.12 333.13 348.12 303.15

[0−1] [0−1] [0−1] [0−1] [0−1] [0−1]

9 6 6 6 6 7

1.056 1.128 1.156 1.191 1.250 1.771

0.004 0.001 0.001 0.001 0.001 0.005

5.547 ± 0.040 6.321 ± 0.014 7.081 ± 0.017 7.892 ± 0.013 9.278 ± 0.015 13.256 ± 0.278

2.898 3.102 3.075 3.089 3.087 4.443

0.040 0.014 0.017 0.013 0.015 0.278

Calvet Calvet Calvet Calvet Calvet Calvet

26 25 25 25 25 27

303.15 303.15

[0−1] [0−1]

8 9

1.333 ± 0.002 1.673 ± 0.006

7.647 ± 0.028 12.338 ± 0.313

3.015 ± 0.028 4.571 ± 0.313

Calvet Calvet

26 27

313.12 333.12 348.13 313.14

[0.137−1] [0.137−1] [0.137−1] [0−1]

6 6 6 6

1.540 ± 0.061 1.745 ± 0.042 1.916 ± 0.035 −2.535 ± 0.021

7.396 ± 0.785 9.907 ± 0.535 11.969 ± 0.452 −13.977 ± 0.494

4.922 ± 0.785 4.055 ± 0.535 3.355 ± 0.452 −12.526 ± 0.494

Calvet Calvet Calvet Calvet

24 24 24 23

313.14

[0−1]

6

−1.007 ± 0.007

−10.041 ± 0.161

−5.898 ± 0.161

Calvet

23

303.15

[0−1]

9

−0.433 ± 0.011

−6.174 ± 0.474

−0.690 ± 0.474

Calvet

26

system (1 + 2)

T (K)

[C1C2Im]Cl + water [C1C4Im]Cl + water [C1C5Im]Cl + water [C1C6Im]Cl + water [C1C1Im][DMP] + water [C1C1Im][DMP] + methanol [C1C1Im][DMP] + ethanol [C1C2Im][DMP] + water [C1C2Im][DMP] + methanol [C1C2Im][DMP] + ethanol [C1C4Im][PF6] + ethanol [C1C4Im][PF6] + ethanol [C1C4Im][PF6] + ethanol [C1C4Im][PF6] + ethanol [C1C4Im][PF6] + 1propanol [C1C4Im][PF6] + 1propanol [C1C4Im][PF6] + 1propanol [C1C4Im][PF6] + 1propanol [C1C4Im][PF6] + 2propanol [C1C4Im][PF6] + 2propanol [C1C4Im][PF6] + 2propanol [C1C4Im][PF6] + 2propanol [C1C4Im][PF6] + 1butanol [C1C4Im][PF6] + 1butanol [C1C4Im][PF6] + 1butanol [C1C4Im][PF6] + 1butanol [C1C4Im][PF6] + 1butanol [C1C2Im][TfO] + water [C1C2Im][TfO] + water [C1C2Im][TfO] + water [C1C2Im][TfO] + water [C1C2Im][TfO] + water [C1C2Im][TfO] + ethanol [C1C4Im][TfO] + water [C1C4Im][TfO] + ethanol [C1C6Im][TfO] + water [C1C6Im][TfO] + water [C1C6Im][TfO] + water [C1C2Im][HSO4] + water [C1C2Im][C1SO4] + water [C1C4Im][C1SO4] + water

298.15 298.15 298.15 298.15 298.15

x1 range

± ± ± ± ± ±

6090

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

± ± ± ± ± ±

apparatus

reference

DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106

Chemical Reviews

Review

Table 3. continued x1 range

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

system (1 + 2)

T (K)

[C1C4Im][C1SO4] + ethanol [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + water [C1C2Im][C2SO4] + methanol [C1C2Im][C2SO4] + ethanol [C1C2Im][C2SO4] + ethanol [C1C2Im][C2SO4] + 1propanol [C1C2Im][C2SO4] + 1butanol [C1C2Im][C1SO3] + water [C1C2Im][C1SO3] + water [C1C2Im][C1SO3] + water [C1C2Im][OAc] + water [C1C2Im][OAc] + water [C1C2Im][OAc] + water [C1C2Im][OAc] + water [C1C2Im][OAc] + water [C1C3Im][OAc] + water [C1C3Im][OAc] + water [C1C3Im][OAc] + water [C1C3Im][OAc] + water [C1C3Im][OAc] + water [C1C2Im][CF3CO2] + water [C1C2Im][CF3CO2] + water [C1C2Im][CF3CO2] + water [C1C2Im][CF3CO2] + water [C1C2Im][SCN] + water [C1C2Im][SCN] + water [C1C2Im][SCN] + water [C1C2Im][DEP] + water [C1C2Im][DEP] + water

303.15

[0−1]

11

1.099 ± 0.023

10.680 ± 0.433

3.293 ± 0.433

Calvet

29

298.15

[0.75−1]

nc

−0.692 ± 0.001

nc

−1.778b ± 0.013

ITC

44

298.15

[0−0.75]

23

−0.646 ± 0.083

−11.304 ± 1.145

−4.724 ± 1.145

IFC

43

303.15

[0−1]

10

−0.727 ± 0.029

−10.031 ± 0.613

−3.346 ± 0.613

Calvet

26

313.14

[0−1]

6

−0.776 ± 0.002

−8.661 ± 0.058

−3.197 ± 0.058

Calvet

25

323.12

[0−1]

6

−0.792 ± 0.008

−8.013 ± 0.189

−3.271 ± 0.189

Calvet

25

333.11

[0−1]

6

−0.799 ± 0.004

−7.653 ± 0.093

−3.300 ± 0.093

Calvet

25

348.12

[0−1]

6

−0.801 ± 0.001

−6.481 ± 0.025

−3.207 ± 0.025

Calvet

25

298.15

[0.89−1]

nc

0.532 ± 0.001

nc

1.029b ± 0.011

ITC

44

298.15

[0.89−1]

nc

1.783 ± 0.012

nc

2.695b ± 0.150

ITC

44

303.15

[0−1]

10

1.100 ± 0.033

11.836 ± 0.633

3.708 ± 0.633

Calvet

27

298.15

[0.94−1]

nc

0.443 ± 0.008

nc

1.606b ± 0.082

ITC

44

298.15

[0.95−1]

nc

0.673 ± 0.005

−22.547 ± 0.070

2.349b ± 0.069

ITC

44

313.14

[0−1]

6

−2.326 ± 0.003

−22.547 ± 0.070

−7.828 ± 0.070

Calvet

23

333.15

[0−1]

6

−2.439 ± 0.002

−22.098 ± 0.045

−7.771 ± 0.045

Calvet

23

348.14

[0−1]

6

−2.494 ± 0.003

−21.473 ± 0.068

−7.764 ± 0.068

Calvet

23

288.15

[0−0.002]

12

−

−50.570 ± 0.232

nc

Isoperibol

87

293.15

[0−0.002]

12

−

−48.887 ± 0.209

nc

Isoperibol

87

298.15

[0−0.002]

12

−

−47.401 ± 0.145

nc

Isoperibol

87

303.15

[0−0.002]

12

−

−45.463 ± 0.141

nc

Isoperibol

87

308.15

[0−0.002]

12

−

−43.201 ± 0.150

nc

Isoperibol

87

288.15

[0−0.001]

12

−

−49.414 ± 0.085

nc

Isoperibol

86

293.15

[0−0.001]

12

−

−48.599 ± 0.065

nc

Isoperibol

86

298.15

[0−0.001]

12

−

−47.344 ± 0.095

nc

Isoperibol

86

303.15

[0−0.001]

12

−

−46.174 ± 0.075

nc

Isoperibol

86

308.15

[0−0.002]

12

−

−45.451 ± 0.094

nc

Isoperibol

86

313.04

[0−1]

6

−2.141 ± 0.001

−14.076 ± 0.012

−6.335 ± 0.012

Calvet

25

323.04

[0−1]

6

−2.103 ± 0.000

−13.022 ± 0.012

−6.246 ± 0.012

Calvet

25

333.06

[0−1]

6

−2.071 ± 0.001

−12.041 ± 0.018

−6.179 ± 0.018

Calvet

25

348.06

[0−1]

6

−2.003 ± 0.001

−10.375 ± 0.017

−6.048 ± 0.017

Calvet

25

313.14

[0−1]

10

−0.446 ± 0.033

2.583 ± 0.539

−0.936 ± 0.539

Calvet

24

333.14

[0−1]

10

−0.431 ± 0.025

4.173 ± 0.495

−0.764 ± 0.495

Calvet

24

348.13

[0−1]

10

−0.394 ± 0.022

5.610 ± 0.462

−0.693 ± 0.462

Calvet

24

313.13

[0−1]

6

−5.600 ± 0.004

−35.180 ± 0.105

−15.328 ± 0.105

Calvet

24

333.13

[0−1]

6

−5.492 ± 0.010

−33.646 ± 0.244

−14.656 ± 0.244

Calvet

24

data

6091

apparatus

reference

DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106

Chemical Reviews

Review

Table 3. continued data

ΔmixH (kJ mol−1)

[0−1]

6

−5.387 ± 0.013

−32.252 ± 0.314

−15.087 ± 0.314

Calvet

24

323.13

[0−1]

6

−1.247 ± 0.003

−9.664 ± 0.060

−3.920 ± 0.060

Calvet

23

333.14

[0−1]

6

−1.225 ± 0.000

−8.804 ± 0.011

−3.842 ± 0.011

Calvet

23

348.14

[0−1]

6

−1.174 ± 0.001

−7.808 ± 0.021

−3.824 ± 0.021

Calvet

23

358.15

[0−1]

28

1.547 ± 0.028

8.142 ± 0.205

4.232 ± 0.205

88

298.15

[0−0.001]

17

−

−53.620 ± 0.434

nc

Flow calorimetry Isoperibol

59

298.15

[0−0.002]

18

−

−57.668 ± 0.844

nc

Isoperibol

61

b

nc

Isoperibol

54

system (1 + 2)

T (K)

[C1C2Im][DEP] + water [C1C2‑OHIm][CF3CO2] + water [C1C2‑OH Im][CF3CO2] + water [C1C2‑OH Im][CF3CO2] + water [C1C4Im][C1SO3] + water [C1C4Im][InCl4] + water [C1C5Im][InCl4] + water [C1C2Im][FeCl4] + water [C1C4Im][FeCl4] + water [C1C4Im][Ala] + water [C1C4Im][Ala] + water [C1C4Im][Ala] + water [C1C4Im][Ala] + water [C1C4Im][Ala] + water [C1C2Im][Gly] + water [C1C2Im][Gly] + water [C1C2Im][Gly] + water [C1C2Im][Gly] + water [C1C2Im][Gly] + water [C1C2Im][Gly] + water [C1C4Im][Gly] + water [C1C4Im][Gly] + water [C1C4Im][Gly] + water [C1C4Im][Gly] + water [C1C4Im][Gly] + water [C1C4Im][Gly] + water [C1C3Im][Val] + water [C1C3Im][Val] + water [C1C3Im][Val] + water [C1C3Im][Val] + water [C1C3Im][Val] + water [C1C3Im][Val] + water [C1C2Im][GaCl4] + water [bPy][BF4] + water [bPy][BF4] + water [bPy][BF4] + methanol [bPy][BF4] + methanol [bPy][BF4] + ethanol [bPy][BF4] + ethanol [bPy][BF4] + 1propanol [bPy][BF4] 1-propanol [b2mPy][BF4] + water [b2mPy][BF4] + water [b2mPy][BF4] + methanol [b2mPy][BF4] + methanol [b2mPy][BF4] + ethanol [b2mPy][BF4] + ethanol [b2mPy][BF4] + 1propanol [b2mPy][BF4] + 1propanol

348.12

x1 range

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

apparatus

reference

298.15

nc

nc

−

−76.600

298.15

[0−0.0005]

12

−

−59.298 ± 0.415

nc

Isoperibol

54

298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15

[0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.001] [0−0.002]

5 5 5 5 20 6 5 5 5 5 26 7 5 5 5 5 27 5 5 5 5 5 25 18

− − − − − − − − − − − − − − − − − − − − − − − −

−57.790 −57.170 −56.769 −56.822 −58.834 −33.725 −31.405 −30.803 −29.031 −27.547 −34.300 −45.094 −45.009 −43.975 −43.102 −41.646 −45.724 −54.368 −53.944 −53.685 −53.496 −53.116 −55.265 −73.548

nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc nc

Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol Isoperibol

58 58 58 58 58 60 60 60 60 60 60 57 57 57 57 57 57 52 52 52 52 52 52 55

298.15 318.15 298.15 318.15 298.15 318.15 298.15

[0−1] [0−1] [0−1] [0−1] [0−1] [0−1] [0.54−1]

19 17 21 17 21 22 6

1.496 2.296 1.502 2.039 1.017 1.793 0.310

± ± ± ± ± ± ±

0.012 0.009 0.014 0.009 0.012 0.008 0.009

14.734 17.939 14.974 17.614 11.885 13.361 nc

± ± ± ± ± ±

0.251 0.167 0.307 0.179 0.268 0.196

4.795 6.381 6.168 4.307 4.995 3.281 2.058

± ± ± ± ± ± ±

0.251 0.167 0.307 0.179 0.268 0.196 0.369

Calvet Calvet Calvet Calvet Calvet Calvet Calvet

35 35 35 35 35 35 35

318.15 298.15 318.15 298.15

[0−1] [0−1] [0−1] [0−1]

19 17 15 17

1.969 1.384 1.925 1.631

± ± ± ±

0.334 0.003 0.006 0.012

15.445 13.090 16.257 12.222

± ± ± ±

0.334 0.294 0.113 0.242

3.225 4.508 6.731 5.419

± ± ± ±

0.334 0.294 0.113 0.242

Calvet Calvet Calvet Calvet

35 30 30 30

318.15

[0−1]

18

2.050 ± 0.007

17.571 ± 0.136

9.547 ± 0.136

Calvet

30

298.15

[0−1]

18

1.928 ± 0.009

15.449 ± 0.163

7.170 ± 0.163

Calvet

30

318.15

[0−1]

18

2.434 ± 0.007

18.269 ± 0.124

9.485 ± 0.124

Calvet

30

298.15

[0.54−1]

6

2.088 ± 0.025

nc

6.685 ± 0.313

Calvet

30

318.15

[0−1]

17

2.500 ± 0.009

19.040 ± 0.222

9.124 ± 0.222

Calvet

30

6092

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.294 0.260 0.284 0.273 0.344 0.080 0.136 0.123 0.054 0.086 0.411 0.063 0.052 0.060 0.081 0.100 0.099 0.116 0.118 0.129 0.119 0.114 0.024 1.815

DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106

Chemical Reviews

Review

Table 3. continued x1 range

ΔmixH (kJ mol−1)

system (1 + 2)

T (K)

[b2mPy][BF4] + 1butanol [b3mPy][BF4] + water [b3mPy][BF4] + water [b3mPy][BF4] + water [b3mPy][BF4] + methanol [b3mPy][BF4] + methanol [b3mPy][BF4] + ethanol [b3mPy][BF4] + ethanol [b3mPy][BF4] + ethanol [b3mPy][BF4] + 1propanol [b3mPy][BF4] + 1propanol [b3mPy][BF4] + 1butanol [b4mPy][BF4] + water [b4mPy][BF4] + water [b4mPy][BF4] + methanol [b4mPy][BF4] + methanol [b4mPy][BF4] + ethanol [b4mPy][BF4] + ethanol [b4mPy][BF4] + 1propanol [b4mPy][BF4] + 1propanol [b4mPy][BF4] + 1butanol [C1C4Pip][N(CN)2] + water [C1C2Pip][C2SO4] + water [C1C4Pip][NTf2] + ethanol [C1C4Pip][NTf2] + 1propanol [C1C6Pip][NTf2] + ethanol [C1C6Pip][NTf2] + 1propanol [C1C2Morph][C2SO4] + water [C1C4Pyrro][N(CN)2] + water [C1C2Pyrro][C2SO4] + water [C1C4Pyrro][NTf2] + water [C1C4Pyrro][NTf2] + methanol [C1C4Pyrro][NTf2] + 1butanol [C1C4Pyrro][NTf2] + 1hexanol [C1C4Pyrro][NTf2] + 1octanol [N1114][NTf2] + methanol [N1114][NTf2] + ethanol [N1114][NTf2] + ethanol [N1114][NTf2] + ethanol

318.15

[0.5−1]

7

2.509 ± 0.049

298.15 303.15 318.15 298.15

[0−1] [0−1] [0−1] [0−1]

23 8 24 23

1.360 2.260 1.972 1.469

318.15

[0−1]

18

2.154 ± 0.020

298.15

[0−1]

26

303.15

[0−1]

318.15

data

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

apparatus

reference

10.036 ± 0.196

Calvet

30

± ± ± ±

0.314 0.093 0.241 0.246

Calvet Calvet Calvet Calvet

32 26 32 32

13.789 ± 0.389

5.013 ± 0.389

Calvet

32

1.924 ± 0.033

16.942 ± 0.619

5.096 ± 0.619

Calvet

32

10

2.496 ± 0.029

15.626 ± 0.574

7.677 ± 0.574

Calvet

27

[0−1]

19

2.483 ± 0.017

18.090 ± 0.337

7.073 ± 0.337

Calvet

32

298.15

[0−1]

16

2.119 ± 0.007

10.532 ± 0.450

7.296 ± 0.450

Calvet

32

318.15

[0−1]

21

2.622 ± 0.011

15.913 ± 0.517

7.197 ± 0.517

Calvet

32

318.15

[0−1]

12

2.752 ± 0.009

12.629 ± 0.509

9.249 ± 0.509

Calvet

32

298.15 318.15 298.15

[0−1] [0−1] [0−1]

21 21 19

1.581 ± 0.009 2.019 ± 0.014 1.776 ± 0.019

13.733 ± 0.174 16.504 ± 0.263 14.138 ± 0.383

4.429 ± 0.174 5.541 ± 0.263 4.583 ± 0.383

Calvet Calvet Calvet

33 33 33

318.15

[0−1]

23

2.546 ± 0.029

15.590 ± 0.568

9.732 ± 0.568

Calvet

33

298.15

[0−1]

19

2.115 ± 0.018

12.998 ± 0.812

7.441 ± 0.812

Calvet

33

318.15

[0−1]

21

2.760 ± 0.016

21.184 ± 0.300

10.140 ± 0.300

Calvet

33

298.15

[0−0.68 ; 0.97−1]

14

2.246 ± 0.021

10.862 ± 1.262

9.682 ± 1.262

Calvet

33

318.15

[0−1]

19

2.798 ± 0.015

19.831 ± 0.270

10.286 ± 0.270

Calvet

33

318.15

[0−1]

19

2.826 ± 0.018

16.894 ± 0.357

8.713 ± 0.357

Calvet

33

298.15

[0−1]

36

−0.732 ± 0.010

−3.450 ± 0.184

−1.093 ± 0.184

ITC

93

298.15

[0−1]

21

−0.639 ± 0.018

−14.113 ± 0.472

−4.273 ± 0.472

ITC

97

298.15

[0−1]

38

2.161 ± 0.010

10.436 ± 0.190

7.200 ± 0.190

ITC

96

298.15

[0−1]

41

2.242 ± 0.010

12.127 ± 0.184

8.110 ± 0.184

ITC

96

298.15

[0−1]

75

2.071 ± 0.010

10.295 ± 0.177

7.209 ± 0.177

ITC

96

298.15

[0−1]

75

2.269 ± 0.008

11.258 ± 0.148

7.791 ± 0.148

ITC

96

298.15

[0−1]

20

−0.354 ± 0.006

−7.531 ± 0.153

−2.449 ± 0.153

ITC

97

298.15

[0−1]

36

−0.897 ± 0.012

−4.314 ± 0.217

−1.260 ± 0.217

ITC

93

298.15

[0−1]

26

−1.139 ± 0.011

−16.225 ± 0.295

−5.858 ± 0.295

ITC

97

± ± ± ±

0.006 0.008 0.012 0.014

nc 12.312 12.165 13.999 12.598

± ± ± ±

0.314 0.093 0.241 0.246

4.492 5.912 4.979 6.011

298.15

nc

nc

+

4.240 ± 0.530

nc

Isoperibol

63

298.15

nc

nc

+

14.510b ± 0.300

nc

Isoperibol

63

298.15

[0−1]

54

0.855 ± 0.002

5.449 ± 0.029

1.933 ± 0.029

ITC

101

298.15

[0−1]

61

0.991 ± 0.003

6.001 ± 0.075

4.075 ± 0.075

ITC

101

298.15

[0−1]

45

1.088 ± 0.002

5.969 ± 0.060

4.835 ± 0.060

ITC

101

298.15

[0.86−1]

nc

2.979 ± 0.042

nc

8.485 ± 0.487

ITC

44

298.15 308.15 313.15

[0.86−1] [0−1] [0−1]

nc 13 10

2.248 ± 0.003 2.308 ± 0.008 2.370 ± 0.024

nc 15.607 ± 0.409 14.255 ± 0.595

7.828 ± 0.041 6.649 ± 0.474 8.445 ± 0.595

ITC Calvet Calvet

44 100 100

b

6093

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Table 3. continued x1 range

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

system (1 + 2)

T (K)

[N1114][NTf2] + ethanol [N1114][NTf2] + 1propanol [N1114][NTf2] + 1butanol [N1114][NTf2] + 1butanol [N1114][NTf2] + 1butanol [N1114][NTf2] + 1butanol [N1114][NTf2] + 1,2propanediol [N1114][NTf2] + 1,2butanediol [N1114][NTf2] + 2,3butanediol [N2000][NO3] + water [N2226][NTf2] + methanol [N2228][NTf2] + methanol [N22212][NTf2] + methanol [N3000][NO3] + water [N4444]Br + methanol [N4444]Br + methanol [N4444]Br + 1,2ethanediol [N4444]Br + 1,2ethanediol [N8000][H2O4P] + water [N9000][H2O4P] + water [Chol][Glyc] + water [Chol][Glyc] + water [Chol][Glyc] + water [Chol][L] + water [Chol][L] + water [Chol][L] + water [P2224][DEP] + water [P2224][DEP] + water [P2224][DEP] + water [C8Isoqui][SCN] + water [C8Isoqui][SCN] + water [C8Isoqui][SCN] + water [C6Isoqui][SCN] + water [C6Isoqui][SCN] + water [C6Isoqui][SCN] + water

323.15 298.15

[0−1] [0.9−1]

9 nc

2.472 ± 0.047 4.874 ± 0.089

16.593 ± 1.075 nc

8.893 ± 1.075 8.480 ± 1.039

Calvet ITC

100 44

298.15

[0.92−1]

nc

2.150 ± 0.002

nc

8.703 ± 0.018

ITC

44

308.15

[0−1]

13

2.602 ± 0.015

13.521 ± 0.362

8.739 ± 0.362

Calvet

100

313.15

[0−1]

10

2.618 ± 0.025

14.460 ± 0.536

8.938 ± 0.536

Calvet

100

323.15

[0−1]

12

2.688 ± 0.032

15.882 ± 0.665

8.921 ± 0.665

Calvet

100

298.15

[0−1]

55

1.721 ± 0.013

12.055 ± 0.534

10.443 ± 0.534

ITC

99

298.15

[0−1]

55

1.695 ± 0.014

12.360 ± 0.554

12.228 ± 0.554

ITC

99

298.15

[0−1]

55

2.260 ± 0.014

14.521 ± 0.548

9.680 ± 0.548

ITC

99

298.15 303.15

[0−1] [0−1]

15 8

0.623 ± 0.003 2.143 ± 0.029

5.205 ± 0.216 10.107 ± 0.313

1.037 ± 0.216 7.034 ± 0.313

IFC Calvet

42 94

303.15

[0−1]

9

2.112 ± 0.053

11.085 ± 0.636

5.809 ± 0.636

Calvet

94

303.15

[0−1]

9

2.191 ± 0.032

12.556 ± 0.417

4.972 ± 0.417

Calvet

94

298.15 298.15 313.15 298.15

[0−1] nc nc nc

14 nc nc nc

0.766 ± 0.006 + + +

5.082 ± 0.412 16.720b ± 0.170 17.180b ± 0.170 28.660b ± 0.290

3.444 ± 0.412 nc nc nc

IFC Isoperibol Isoperibol Isoperibol

42 89 89 89

298.15

nc

nc

+

30.200b ± 0.300

nc

Isoperibol

89

298.15 298.15 303.15 313.15 323.15 303.15 313.15 323.15 313.11 333.11 348.11 298.15

[0−0.001] [0−0.2] [0−0.66] [0−0.64] [0−0.66] [0−84] [0−0.83] [0−0.84] [0−1] [0−1] [0−1] [0−1]

16 17 10 11 9 10 10 9 6 6 6 29

+ + −4.777 ± 0.444 −2.970 ± 0.131 −1.782 ± 0.295 −13.562 ± 1.213 −9.798 ± 1.325 −6.360 ± 0.175 −2.532 ± 0.003 −2.270 ± 0.005 −2.079 ± 0.002 −0.395 ± 0.004

19.530 ± 0.192 31.862 ± 0.165 −51.043 ± 6.272 −23.729 ± 1.792 −19.314 ± 3.705 −213.736 ± 21.721 −178.249 ± 26.703 −110.867 ± 3.313 −23.540 ± 0.064 −20.831 ± 0.117 −18.466 ± 0.048 −4.768 ± 0.099

nc nc 12.823 ± 6.272 −0.034 ± 1.792 5.057 ± 3.705 −61.664 ± 21.721 −57.065 ± 26.703 −21.310 ± 3.313 −5.560 ± 0.064 −5.077 ± 0.117 −4.876 ± 0.048 −1.000 ± 0.099

Isoperibol Isoperibol Calvet Calvet Calvet Calvet Calvet Calvet Calvet Calvet Calvet Calvet

91 91 21 21 21 21 21 21 24 24 24 84

303.15

[0−1]

29

−0.400 ± 0.006

4.885 ± 0.155

−1.411 ± 0.155

Calvet

84

308.15

[0−1]

30

−0.418 ± 0.010

5.364 ± 0.231

−1.447 ± 0.231

Calvet

84

298.15

[0−1]

60

−0.104 ± 0.006

−0.570 ± 0.466

−2.131 ± 0.466

ITC

85

303.15

[0−1]

60

−0.117 ± 0.006

−0.448 ± 0.444

−2.056 ± 0.444

ITC

85

308.15

[0−1]

60

−0.109 ± 0.005

−0.579 ± 0.392

−2.340 ± 0.392

ITC

85

data

apparatus

reference

a

Values reported in italic were obtained by extrapolation of the calculated data out of the experimentally studied composition range. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively. bValues taken directly from each reference as authors did not report raw data (nc).

C1C2Im+ in DMP− based ionic liquids seems to slightly favor mixing with methanol. In Figures 16, 17, and 18 are depicted the mixing enthalpies of the imidazolium and pyridinium ionic liquids based on different anions with ethanol, 1-propanol, and 1-butanol, respectively. Among the systems reported in the literature, only ([C1CnIm][DMP] + ethanol), where n = 1, 2, have negative mixing enthalpies.19,20 For other (ionic liquid + ethanol) binary mixtures, values of ΔmixH are positive over all composition

([bnmPy][BF4],30,32,33 an endothermic mixing process is observed. ΔmixH does not change significantly with composition for a series of three pyridinium ionic liquids, and no significant influence of the position of the methyl group on the aromatic ring on the mixing properties was observed even if slightly higher values for ([b4mPy][BF4] + methanol) were reported by Ortega et al.33 Figure 15d presents the variation of the partial excess molar enthalpies for ionic liquid and methanol at infinite dilution, and it can be observed that changing the cation from C1C1Im+ to 6094

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Figure 14. Temperature effect on calorimetric properties of (ionic liquid + alcohol) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH, as a function of composition and temperature: filled symbols and solid lines for T = 298.15 K; open symbols and dashed lines for T = 318.15 K or T = 323.15 K. (b) H̅ iE, ∞, for components in binary mixtures. Filled and open symbols correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ⬡, ([C1C4Im][PF6] + 2-propanol);49 ○, ([C1C2Im][BF4] + CF3CH2OH);22 ∇, ([C1C4Im][BF4] + CF3CH2OH);22 □, ([b2mPy][BF4] + ethanol);30 ◇, ([b3mPy][BF4] + ethanol);32 and Δ, ([b4mPy][BF4] + ethanol).33 The lines in plot (a) represent data fittings using eq 10 for ΔmixH. For all systems ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 15. Calorimetric properties of (ionic liquid + methanol) binary mixtures at T = 298.15 K and p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ●, [C1C1Im][DMP];19 ○, [C1C2Im][DMP];20 □, [b2mPy][BF4];30 ■, [b3mPy][BF4];32 and ▲, [b4mPy][BF4].33 The lines represent data fittings using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

range. Nebig et al.36 observed that increasing the length of alkylchain in the imidazolium cation of [C1CnIm][NTf2] from n = 2 to 6 disfavors the mixing process. The difference between ΔmixH for systems differing by only two carbon atoms in the alkyl-chain {([C1C4Im][BF4] + ethanol)29 vs ([C1C6Im][BF4] + ethanol),27 ([C1C2Im][TfO] + ethanol)27 vs ([C1C4Im][TfO] + ethanol)}27 is within their mutual experimental uncertainty. In accordance with the data determined by Navas et al.30 and Ortega et al.32,33 for the systems containing [b2mPy][BF4], [b3mPy][BF4], and [b4mPy][BF4], the difference in ΔmixH is not significant and varies with composition. On the contrary, in the case of ([C1C1Im][DMP] + ethanol)19 and ([C1C2Im][DMP] + ethanol),20 it was observed that increasing the length of alkyl chain decreases the values of H̅ iE, ∞, which become more negative. However, both values, ΔmixH at equimolar composition and H̅ 2E, ∞, increase monotonously with the number of carbon atoms in the alcohol (from methanol to butanol) for a given ionic liquid as depicted from Figures 16, 17, and 18 and in Table 3.

exothermic mixing process of the studied (ionic liquid + ketones) binary mixtures. A subtle monotonous tendency in ΔmixH can be observed (Figure 19d), the enthalpy of mixing slightly changing to less negative values as the number of carbon atoms, either in the alkyl chain of imidazolium cation or ketone, increases. The effect of the structure of ionic liquid on the mixing properties with nitromethane was also investigated.28,29 The mixing enthalpies for several imidazolium ([C1C4Im][C1SO4], [C 1 C 2 Im][C 2 SO 4 ], [C 1 C 2 Im][TfO], [C 1 C 4 Im][TfO], [C1C4Im][BF4], and [C1C6Im][BF4]) ionic liquids and also one pyridinium-based ionic liquid ([b3mPy][BF4]) with CH3NO2 were determined experimentally at 303.15 K and 0.1 MPa over the whole composition range. The values are represented in Figure 19 together with the curve fits. It can be observed that ΔmixH for all studied systems, except for ([C1C4Im][TfO] + CH3NO2), are negative meaning that the interactions in (ionic liquid + CH3NO2) are more favorable than in the ideal mixture. Comparisons of ΔmixH as well as H1̅ E, ∞ and H̅ 2E, ∞ for ([C1C4Im][BF4] + CH3NO2) and ([C1C6Im][BF4] + CH3NO2) indicate that an increase in the number of carbon atoms in alkyl chain disfavors miscibility although both mixtures behave similarly at limiting dilution with a value of H̅ iE, ∞ less negative for CH3NO2 than for the ionic liquid.

4.3. (Ionic Liquid + Nonassociative Compound) Binary Mixtures

Nebig et al.36 have measured enthalpies when mixing [C1C4Im][NTf2] and [C1C6Im][NTf2] with acetone, 1-butanone, and 3pentanone.36 The experimental values of ΔmixH are negative (Figure 19a) in the whole composition range, indicating an 6095

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Figure 16. Calorimetric properties of (ionic liquid + ethanol) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E, ∞ and H̅ 2E, ∞, respectively, for ●, [C1C2Im][NTf2] from Nebig et al.36 at T = 323.15 K; ○, [C1C6Im][NTf2] from Nebig et al.36 at T = 353.15 K; ■ [C1C4Im][BF4] from Iglesias-Otero et al.29 at T = 303.15 K; □, [C1C6Im][BF4] from Garcı ́a-Miaja et al.27 at T = 303.15 K; ▲, [b2mPy][BF4] data from Navas et al.30 at T = 298.15 K; △, [b3mPy][BF4] data from Ortega et al.32 at T = 298.15 K; gray ▲, [b4mPy][BF4] data from Ortega et al.33 at T = 298.15 K; ⬢, [C1C1Im][DMP] from He et al.19 at T = 298.15 K; ⬡, [C1C2Im][DMP] from Ren et al.20 at T = 298.15 K; ◆, [C1C2Im][TfO] data from Garcı ́aMiaja et al.27 at T = 303.15 K; ◇, [C1C4Im][TfO] from Garcı ́a-Miaja et al.27 at T = 303.15 K; ▼, [C1C4Im][C1SO4] from Iglesias-Otero et al.29 at T = 303.15 K; ▽, [C1C2Im][C2SO4] data from Garcı ́a-Miaja et al.27 at T = 303.15 K; and +, [C1C4Im][PF6] from Li et al.49 at T = 298.15 K. The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 17. Calorimetric properties of (ionic liquid + 1-propanol) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies,H1̅ E , and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ●, [C1C2Im][NTf2] data from Nebig et al.36 at T = 323.15 K; ○, [C1C2Im][PF6] data from Li et al.49 at T = 318.15 K; □, [b2mPy][BF4] data from Navas et al.30 at T = 318.15 K; ■, [b3mPy][BF4] data from Ortega et al.32 at T = 318.15 K; and ▲, [b4mPy][BF4] data from Ortega et al.33 at T = 318.15 K. The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems, ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Waliszewski et al.63 determined the enthalpies of solution of several ionic liquids in acetonitrile. The experimental values used to calculate the partial excess molar enthalpy at infinite dilution for the ionic liquid are reported in Table 4. Because the ΔsolH were only measured in a limited composition range, the fitted function only allows the prediction of the sign of ΔmixH at the equimolar composition. The calculated values for ΔmixH as well as H̅ 2E are negative for the imidazolium ionic liquids studied, with significantly more negative values for BF4− based ionic liquids than for NTf2− based ones. Ionic liquids based on pyrrolidinium cations instead of imidazolium show positive values of the mixing and partial molar excess enthalpies, respectively. The experimental mixing enthalpies of [C1C2Im][NTf2] with n-hexane, cyclohexane, 1-hexene, cyclohexene, and benzene were

measured either at 353.15 or 323.15 K and are presented in Figure 20a (upper plot).36−41 Because some of these apolar compounds are only partially miscible with the ionic liquids, the experimental measurements were performed at high pressures in order to cover the whole composition range. Figure 20a (upper plot) represents also the values of ΔmixH for toluene and chloroform, which were calculated from experimentally determined partial molar excess enthalpies measured at a narrow concentration range, at 298.15 K and at atmospheric pressure.48 The enthalpies of mixing and the partial molar excess enthalpies are positive for aliphatic compounds (n-hexane, cyclohexane, hexene, and cyclohexene) and negative for aromatic species (benzene and toluene) and for chloroform. The introduction of one double bond in the aliphatic chain of the nonionic 6096

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Figure 18. Calorimetric properties of (ionic liquid + 1-butanol) binary mixtures at T = 318.15 K and p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ○, [C1C2Im][PF6];49 □, [b2mPy][BF4];30 ■, [b3mPy][BF4];32 and ▲, [b4mPy][BF4].33 The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Figure 19. Calorimetric properties of (ionic liquid + polar compound) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞, for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ●, ([C1C4Im][BF4] + acetone); ■, ([C1C6Im][BF4] + acetone); ▼, ([C1C4Im][BF4] + 1-butanone); ◆ ([C1C6Im][BF4] + 1-butanone); ▼, ([C1C6Im][BF4] + 3-pentanone), using reported data for ΔmixH at T = 353.15 K from Nebig et al.;36 and for ○, ([C1C2Im][C2SO4] + nitromethane); □, ([C1C2Im][TfO] + nitromethane); △, ([C1C4Im]|TfO] + nitromethane); ◇, ([C1C4Im][C1SO4] + nitromethane); ▽, ([C1C4Im][BF4] + nitromethane); ⬡, ([C1C6Im][BF4] + nitromethane); +, ([b3mPy][BF4] + nitromethane), using reported data for ΔmixH at T = 303.15 K from Romanı ́ et al.28,29 The lines represent data fittings using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

carbon of the imidazolium ring as in [C1C1C4Im][NTf2] (compared with [C1C4Im][NTf2]) leads to a more positive enthalpy of mixing with 1,3-cyclohexadiene. The structure of the ionic liquid also influences calorimetric properties of the mixtures with apolar compounds as can be seen from the data for n-hexane and benzene in several ionic liquids, plotted in Figure 21 and listed in Table 5. It can be concluded from the work of Nebig et al.36−38 that increasing the number of the carbon atoms in the alkyl side-chain of the imidazolium cation leads to a more endothermic mixing with n-hexane, ΔmixH increasing by about 0.1 kJ mol−1 for every two additional carbon atoms on the alkyl side chain. Limiting excess enthalpies are also influenced by the number of carbons in the alkyl side chain of the cation, especially when changing the number of −CH2 groups in the chain from 2 to 4. Mixing processes of various ionic liquids with benzene are represented in Figure 21 (lower plots). ΔmixH is negative for all

component of the mixture does not seem to affect the interactions with [C1C2Im][NTf2], as can be seen by comparing the values for n-hexane with 1-hexene or cyclohexane with cyclohexene. On the other hand, the presence of double bonds in the aliphatic chain of the cation influences significantly the limiting values of partial molar excess enthalpies (Figure 20d and Table 5) that become more negative. Another example showing the effect of the structure of different apolar compounds on their enthalpies of mixing with one ionic liquid, [C1C4Im][NTf2], is graphically represented in Figure 20 (lower plots). Negative values of ΔmixH are observed for benzene and toluene36 while for n-hexane,36 methylcyclohexane,36 and 1,3-cyclohexadiene,45 the enthalpy of mixing is positive. The values of ΔmixH for 1,3-cyclohexadiene are intermediate between the values for cyclohexene and benzene, the enthalpy of mixing for benzene being the lower of the three. The introduction of an additional methyl group on the C2 6097

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Table 4. Molar Enthalpy of Mixing, ΔmixH at Equimolar Composition, and Calculated Partial Molar Excess Enthalpies at Infinite Dilution, H̅ iE, ∞ of (Ionic Liquid + Polar Compound) Binary Mixtures at p = 0.1 MPa Reported in the Literaturea system (1 + 2)

T (K)

x1 range

data

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

apparatus

reference 81

−3.170 ± 0.309 −2.887 ± 0.416 −3.082 ± 0.297

2-Drop calorimeter Differential calorimeter IFC IFC IFC

36 36 36

−9.384 ± 0.347

−3.227 ± 0.347

IFC

36

−0.992 ± 0.016

−9.289 ± 0.282

−2.752 ± 0.282

IFC

36

18

−0.482 ± 0.001

−1.492 ± 0.023

−1.797 ± 0.023

Calvet

83

b

95

92

[C1C2Im][BF4] + acetone

298.15

[0−1]

18

−0.209 ± 0.000

−0.564 ± 0.010

−0.787 ± 0.010

[C1C4Im][BF4] + acetone

298.15

nc

nc

−

−10.210b ± 0.270

nc

[C1C4Im][NTf2] + acetone [C1C6Im][NTf2] + acetone [C1C4Im][NTf2] + 1butanone [C1C6Im][NTf2] + 1butanone [C1C6Im][NTf2] + 3pentanone [C1C2Im][BF4] + N-methyl2-pyrrolidone [N2000][NO3] + N-methyl-2pyrrolidone [N3000][NO3] + N-methyl-2pyrrolidone [N4000][NO3] + N-methyl-2pyrrolidone [N2‑O‑1000][NO3] + Nmethyl-2-pyrrolidone [1,2,4-Triz][N(CN)2] + Nmethyl-2-pyrrolidone [1,2,4-Triz][N(CN)2] + Nmethyl-2-pyrrolidone [1,2,4-Triz][N(CN)2] + Nmethyl-2-pyrrolidone [1,2,4-Triz][N(CN)2] + Nmethyl-2-pyrrolidone [C1C4Im][BF4] + nitromethane [C1C4Im][BF4] + nitromethane [C1C6Im][BF4] + nitromethane [b3mPy][BF4] + nitromethane [C1C2Im][C2SO4] + nitromethane [C1C4Im][C1SO4] + nitromethane [C1C2Im][TfO] + nitromethane [C1C4Im][TfO] + nitromethane [N1114][NTf2] + dimethylformamide [N1114][NTf2] + dimethylformamide [N1114][NTf2] + dimethylformamide [C1C2Im][BF4] + acetonitrile [C1C4Im][BF4] + acetonitrile [C1C4Im][BF4] + acetonitrile [C1C2Im][NTf2] + acetonitrile [C1C4Pyrro][NTf2] + acetonitrile [C1C2Im][BF4] + pyridine

353.15 353.15 353.15

[0−1] [0−1] [0−1]

12 13 12

−1.096 ± 0.020 −0.984 ± 0.023 −1.059 ± 0.019

−9.742 ± 0.309 −9.343 ± 0.416 −9.598 ± 0.297

353.15

[0−1]

13

−1.040 ± 0.019

353.15

[0−1]

12

298.15

[0−1]

[C1C2Im][BF4] + 2methylpyridine [C1C2Im][BF4] + 3methylpyridine

298.15

nc

1

−3.494 ± 0.025

−12.740 ± 0.070

−10.790 ± 0.090

298.15

nc

1

−3.300b ± 0.024

−12.670b ± 0.060

−10.100b ± 0.080

298.15

nc

1

−3.046b ± 0.014

−11.460b ± 0.060

−8.550b ± 0.060

298.15

nc

1

−2.658b ± 0.036

−11.000b ± 0.200

−7.500b ± 0.100

b

b

90

298.15

nc

1

+

10.900 ± 1.100

nc

Heat flow Calorimeter Heat flow Calorimeter Heat flow Calorimeter Heat flow Calorimeter Calvet

303.15

nc

1

+

11.100b ± 1.800

nc

Calvet

92

308.15

nc

1

+

11.200b ± 0.930

nc

Calvet

92

313.15

nc

1

+

11.280b ± 0.350

nc

Calvet

92

298.15

nc

nc

−

−5.110b ± 0.160

nc

90

303.15

[0−1]

10

−0.456 ± 0.005

−3.353 ± 0.105

−1.658 ± 0.105

Differential calorimeter Calvet

29

303.15

[0−1]

9

−0.159 ± 0.001

−0.812 ± 0.014

−0.462 ± 0.014

Calvet

28

303.15

[0−1]

10

−0.457 ± 0.008

−2.943 ± 0.152

−1.293 ± 0.152

Calvet

28

303.15

[0−1]

9

−0.621 ± 0.002

−3.386 ± 0.022

−1.578 ± 0.022

Calvet

28

303.15

[0−1]

9

−0.445 ± 0.005

−2.286 ± 0.062

−1.271 ± 0.062

Calvet

29

303.15

[0−1]

7

−0.200 ± 0.004

−1.172 ± 0.046

−0.432 ± 0.046

Calvet

28

303.15

[0−1]

9

0.056 ± 0.002

0.591 ± 0.087

−0.336 ± 0.087

Calvet

28

308.15

[0−1]

10

−1.114 ± 0.003

−7.839 ± 0.069

−3.660 ± 0.069

Calvet

100

313.15

[0−1]

9

−1.120 ± 0.006

−7.789 ± 0.136

−3.687 ± 0.136

Calvet

100

323.15

[0−1]

9

−1.140 ± 0.004

−8.113 ± 0.080

−3.765 ± 0.080

Calvet

100

298.15

[0−0.001]

10

−

−4.476 ± 0.020

nc

Isoperibol

63

298.15

[0−0.001]

10

−

−4.675 ± 0.046

nc

Isoperibol

63

298.15

nc

nc

−

−5.060b ± 0.500

nc

90

298.15

nc

nc

−

−2.180b ± 0.340

nc

Differential calorimeter Isoperibol

63

298.15

nc

nc

+

0.440b ± 0.040

nc

Isoperibol

63

298.15

[0−1]

18

−0.450 ± 0.001

−1.487 ± 0.025

−1.750 ± 0.025

82

298.15

[0−1]

18

−0.403 ± 0.001

−1.066 ± 0.022

−3.190 ± 0.022

298.15

[0−1]

18

−0.363 ± 0.001

−1.201 ± 0.016

−2.183 ± 0.016

2-Drop calorimeter 2-Drop calorimeter 2-Drop calorimeter

b

6098

95 95 95

82 82

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Table 4. continued data

ΔmixH (kJ mol−1)

H1̅ E, ∞ (kJ mol−1)

H̅ 2E, ∞ (kJ mol−1)

[0−1]

18

−0.426 ± 0.001

−1.256 ± 0.022

−2.525 ± 0.022

298.15

[0−1]

59

−1.237 ± 0.010

−2.581 ± 0.142

−2.434 ± 0.142

298.15

[0−1]

18

−1.215 ± 0.003

−4.061 ± 0.062

−3.401 ± 0.062

298.15

nc

nc

−

−5.570b ± 0.090

nc

298.15

nc

nc

−

−12.180b ± 0.200

nc

298.15

nc

nc

−

−2.300b ± 0.160

nc

nc

−

−1.070 ± 0.080

nc

system (1 + 2)

T (K)

[C1C2Im][BF4] + 4methylpyridine [C1C4Pyrro][NTf2] + thiophene [C1C2Im][BF4] + dimethyl sulfoxide [C1C4Im][BF4] + dimethyl sulfoxide [C1C4Im][BF4] + dimethylformamide [C1C4Im][BF4] + propylene carbonate [C1C4Im][BF4] + ethyl ethanoate

298.15

298.15

x1 range

nc

b

apparatus

reference

2-Drop calorimeter ITC

82

2-Drop calorimeter Differential calorimeter Differential calorimeter Differential calorimeter Differential calorimeter

101 81 90 90 90 90

a

Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively. bValues taken directly from each reference as authors did not report raw data (nc).

Figure 20. Calorimetric properties of (ionic liquid + apolar compound) binary mixtures. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ●, ([C1C2Im][NTf2] + n-hexane) at T = 353.15 K and p = 0.1 MPa;36 ○, ([C1C2Im][NTf2] + cyclohexane) at T = 323.15 K and p = 1.307 MPa;41 ▲, ([C1C2Im][NTf2] + 1-hexene) at T = 323.15 K and p = 1.342 MPa;41 △, ([C1C2Im][NTf2] + cyclohexene) at T = 323.15 K and p = 1.307 MPa;41 ◆, ([C1C2Im][NTf2] + benzene) at T = 323.15 K and p = 1.342 MPa;41 ◇, ([C1C2Im][NTf2] + toluene) at T = 298.15 K and p = 0.1 MPa;48⬢ ([C1C2Im][NTf2] + chloroform) at T = 298.15 K and p = 0.1 MPa;48 ▼, ([C1C4Im][NTf2] + n-hexane) at T = 363.15 K and p = 0.1 MPa;36 ▽, ([C1C4Im][NTf2] + methylcyclohexane) at T = 363.15 K and p = 0.1 MPa;36 ■, ([C1C4Im][NTf2] + benzene) at T = 363.15 K and p = 0.1 MPa;36 □, ([C1C4Im][NTf2] + toluene) at T = 363.15 K and p = 0.1 MPa;36 and +, ([C1C4Im][NTf2] + 1,3-cyclohexadiene) at T = 303.15 K and p = 0.1 MPa.45 The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. Reported data for ΔmixH and H̅ 2E were obtained from refs 36 and 41 and from refs 45 and 49, respectively. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

Thermodynamic quantities of mixing can provide valuable unique information about molecular interactions and microscopic structure of the mixture. Nevertheless, these macroscopic energetic quantities alone are not sufficient to characterize the details of the interactions at the molecular scale. Further information (e.g., from spectroscopy, X-ray and neutron diffraction, and molecular simulation) would be necessary in order to unambiguously elucidate the molecular interactions and structure of the mixtures. The data reviewed herein allows the establishment of a number of semiempirical trends that were presented in section 4. A variety of thermodynamic behaviors exist in mixtures containing ionic liquids depending on the molecular structure of both components of the mixture with consequences on the sign

the ionic liquids, and it is observed that mixing enthalpy decreases when the size of the alkyl chain in [C1CnIm][NTf2] ionic liquids increases. The same behavior is observed in the case of [C1C4Pyrro][NTf2] and [C1C6Pyrro][NTf2].38 Temperature effects on calorimetric properties are seen in Figure22.

5. CONCLUSIONS Special attention was paid in the present review to the terminology and nomenclature of the main quantities treated in this review, and all the reported values were recalculated in an uniform way in order to facilitate the comparison and to provide a solid formal basis to future work in the field. 6099

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Table 5. Molar Enthalpy of Mixing, ΔmixH at Equimolar Composition, and Calculated Partial Molar Excess Enthalpies at Infinite Dilution, H̅ iE, ∞ of (Ionic Liquid + Apolar Compound) Binary Mixtures Reported in the Literaturea system (1 + 2)

T (K)

p (MPa)

[C1C2Im][NTf2] + nhexane [C1C2Im][NTf2] + cyclohexane [C1C2Im][NTf2] + 1hexene [C1C2Im][NTf2] + cyclohexene [C1C2Im][NTf2] + benzene [C1C2Im][NTf2] + toluene [C1C2Im][NTf2] + chloroform [C1C4Im][NTf2] + nhexane [C1C4Im][NTf2] + methylcyclohexane [C1C4Im][NTf2] + benzene [C1C4Im][NTf2] + benzene [C1C4Im][NTf2] + toluene [C1C4Im][NTf2] + 1,3-cyclohexadiene [C1C1C4Im][NTf2] + 1,3-cyclohexadiene [C1C6Im][NTf2] + nhexane [C1C6Im][NTf2] + noctane [C1C6Im][NTf2] + methylcyclohexane [C1C6Im][NTf2] + 1octene [C1C6Im][NTf2] + benzene [C1C6Im][NTf2] + toluene [C1C2Im][BF4] + dimethylformamide [C1C4Im][BF4] + dimethylformamide [C1C4Im][BF4] + chloroform [C1C6Im][BF4] + dimethylformamide [C1C6Im][BF4] + chloroform [C1C8Im][BF4] + dimethylformamide [C1C8Im][BF4] + chloroform [C1C4Im][TfO] + nhexane [C1C4Im][TfO] + nheptane [C1C4Im][TfO] + nheptane [C1C4Im][TfO] + 1hexene [C1C6Im][TfO] + 1hexene [C1C2Im][C2SO4] + chloroform [C1C4Pyrro][NTf2] + 1-hexene

353.15

ΔmixH (kJ mol−1)

H1̅ E , ∞ (kJ mol−1)

apparatus

reference

9

0.198 ± 0.014

1.697 ± 1.030

6.770 ± 1.030

IFC

36

[0−1]

8

0.301 ± 0.005

0.936 ± 0.358

6.635 ± 0.358

IFC

41

1.342

[0−1]

8

0.199 ± 0.010

0.339 ± 0.370

3.874 ± 0.370

IFC

41

323.15

1.307

[0−1]

9

0.326 ± 0.011

0.706 ± 0.360

4.994 ± 0.360

IFC

41

323.15

1.342

[0−1]

8

−0.644 ± 0.007

−2.009 ± 0.461

−1.057 ± 0.461

IFC

41

298.15

0.1

[0.975−1]

4

−0.272 ± 0.006

nc

−1.088 ± 0.024

ITC

48

298.15

0.1

[0.904−1]

10

−1.079 ± 0.013

nc

−3.246 ± 0.083

ITC

48

363.15

0.1

[0−1]

9

0.283 ± 0.021

0.833 ± 0.354

4.144 ± 0.354

IFC

36

363.15

0.1

[0−1]

11

0.401 ± 0.006

0.631 ± 0.322

6.908 ± 0.322

IFC

36

363.15

0.1

[0−1]

12

−0.821 ± 0.024

−3.817 ± 0.367

−1.351 ± 0.367

IFC

36

413.15

0.1

[0−1]

13

−0.880 ± 0.012

−4.521 ± 0.252

−1.263 ± 0.252

IFC

36

363.15

0.1

[0−1]

14

−0.537 ± 0.011

−2.605 ± 0.120

−1.693 ± 0.120

IFC

36

303.15

0.1

[0.885−1]

36

0.313 ± 0.005

nc

0.869 ± 0.030

ITC

45

303.15

0.1

[0.907−1]

29

0.648 ± 0.009

nc

1.630 ± 0.060

ITC

45

363.15

0.1

[0−1]

13

0.386 ± 0.014

0.767 ± 0.247

4.376 ± 0.247

IFC

36

363.15

1.548

[0−1]

13

0.298 ± 0.008

0.323 ± 0.365

5.870 ± 0.365

IFC

40

363.15

1.617

[0−1]

13

0.562 ± 0.025

0.814 ± 0.494

5.191 ± 0.494

IFC

40

413.15

0.1

[0−1]

13

0.423 ± 0.017

0.963 ± 0.337

4.836 ± 0.337

IFC

36

363.15

0.1

[0−1]

14

−0.837 ± 0.010

−3.721 ± 0.463

−2.560 ± 0.463

IFC

36

363.15

0.1

[0−1]

12

−0.753 ± 0.004

−1.970 ± 0.157

−2.031 ± 0.157

IFC

36

298.15

0.1

[0−0.66]

14

−0.235 ± 0.005

−2.154 ± 0.088

nc

ITC

51

298.15

0.1

[0−0.59]

9

−0.317 ± 0.008

−3.063 ± 0.154

nc

ITC

51

298.15

0.1

[0.78−0.94]

18

−14.969 ± 2.661

−85.768 ± 11.599

nc

ITC

51

298.15

0.1

[0−0.61]

14

−0.223 ± 0.007

−2.201 ± 0.127

nc

ITC

51

298.15

0.1

[0−0.05]

14

−

1.870 ± 4.567

nc

ITC

51

298.15

0.1

[0−0.31]

14

0.189 ± 0.023

1.579 ± 0.479

nc

ITC

51

298.15

0.1

[0−0.55]

14

1.216 ± 0.051

13.397 ± 1.101

nc

ITC

51

413.15

0.1

[0−1]

13

0.153 ± 0.026

1.293 ± 0.498

3.549 ± 0.498

IFC

37

363.15

0.1

[0−1]

12

0.097 ± 0.015

0.704 ± 0.270

2.220 ± 0.270

IFC

37

413.15

0.1

[0−1]

13

0.179 ± 0.036

1.575 ± 0.688

4.160 ± 0.688

IFC

37

413.15

0.1

[0−1]

13

0.145 ± 0.009

0.804 ± 0.168

2.590 ± 0.168

IFC

37

363.15

0.1

[0.864−1]

6

0.241 ± 0.005

nc

0.966 ± 0.022

IFC

37

[0.94−1]

nc

−2.036 ± 0.003

nc

−10.236 ± 0.031

ITC

44

[0−1]

11

0.381 ± 0.006

1.115 ± 0.285

2.794 ± 0.285

IFC

39

x1 range

data

0.1

[0−1]

323.15

1.307

323.15

298.15

0.1

363.15

2.239

6100

H̅ 2E , ∞(kJ mol−1)

b

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Table 5. continued T (K)

p (MPa)

x1 range

data

+

413.15

2.239

[0−1]

+

363.15

2.239

+

298.15

+

ΔmixH (kJ mol−1)

H1̅ E , ∞ (kJ mol−1)

apparatus

reference

12

0.335 ± 0.010

0.764 ± 0.207

3.717 ± 0.207

IFC

39

[0−1]

12

−0.821 ± 0.010

−3.185 ± 0.421

−2.034 ± 0.421

IFC

38

0.1

[0−1]

48

−0.972 ± 0.010

−5.418 ± 0.223

−0.809 ± 0.223

ITC

101

413.15

2.342

[0−1]

14

−0.698 ± 0.006

−2.176 ± 0.116

−1.605 ± 0.116

IFC

38

+

363.15

2.135

[0−1]

13

0.363 ± 0.005

1.286 ± 0.243

1.341 ± 0.243

IFC

39

+

363.15

1.720

[0.35−1]

8

0.399 ± 0.022

0.325 ± 0.234

2.863 ± 0.234

IFC

39

+

393.15

2.342

[0−1]

14

−0.998 ± 0.009

−3.579 ± 0.423

−2.827 ± 0.423

IFC

38

+

413.15

2.377

[0−1]

14

−0.832 ± 0.005

−2.585 ± 0.213

−2.063 ± 0.213

IFC

38

298.15

0.1

[0.90−1]

nc

−0.413 ± 0.002

nc

0.246b ± 0.018

ITC

44

system (1 + 2) [C1C4Pyrro][NTf2] 1-heptene [C1C4Pyrro][NTf2] benzene [C1C4Pyrro][NTf2] benzene [C1C4Pyrro][NTf2] toluene [C1C6Pyrro][NTf2] n-pentane [C1C6Pyrro][NTf2] n-hexane [C1C6Pyrro][NTf2] benzene [C1C6Pyrro][NTf2] toluene [N1114][NTf2] + benzene

H̅ 2E , ∞(kJ mol−1)

Values of ΔmixH reported in italics were obtained by extrapolation of the calculated data out of the experimentally studied composition range. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively. bValues taken directly from each reference as authors did not report raw data (nc).

a

Figure 21. Calorimetric properties of (ionic liquid + apolar compound) binary mixtures. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ●, ([C1C2Im][NTf2] + n-hexane) at T = 353.15 K and p = 0.1 MPa;36 ○, ([C1C4Im][NTf2] + n-hexane) at T = 363.15 K and p = 0.1 MPa;36 ▲, ([C1C6Im][NTf2] + n-hexane) at T = 363.15 K and p = 0.1 MPa;36 △, ([C1C4Im][TfO] + n-hexane) at T = 413.15 K and p = 0.1 MPa;37 ◆, ([C1C6Pyrro][NTf2] + n-hexane) at T = 363.15 K and p = 0.1 MPa;39 ■, ([C1C2Im][NTf2] + benzene) at T = 323.15 K and p = 1.342 MPa;41 □, ([C1C4Im][NTf2] + benzene) at T = 363.15 K and p = 0.1 MPa;36 ⬢, ([C1C6Im][NTf2] + benzene) at T = 363.15 K and p = 0.1 MPa;36 ▼, ([C1C4Pyrro][NTf2] + benzene) at T = 363.15 K and p = 2.239 MPa;38 ▽, ([C1C6Pyrro][NTf2] + benzene) at T = 393.15 K and p = 2.342 MPa;38 +, ([N1114][NTf2] + benzene) at T = 298.15 K and p = 0.1 MPa44 The solid and dashed lines represent fitted data and extrapolated data using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. Reported data for ΔmixH and H1̅ E were obtained from refs 36, 39, and 41 and from ref 44, respectively. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

and magnitude of the enthalpy of mixing. The two sets of accurate data that are reported in this work show that, when mixed with other ionic liquids, both positive and negative enthalpies of mixing are found, but they are relatively small in absolute value, with no significant differences between the partial molar excess enthalpies at infinite dilution of the two salts. The trends observed can be explained by a balance between electrostatic and dispersion interactions between the ions in the mixture.

The partial molar excess enthalpies of polar associative compounds, like water or different alcohols, in mixtures containing ionic liquids are 1 order of magnitude larger than those found when both components are ionic. A wide range of ionic liquids was studied in mixtures with water, the enthalpy of mixing being positive for a small number of systems and negative for the majority of the ionic liquids studied. The enormous span of the partial molar enthalpies calculated from the experimental data show clearly that the interactions between different ions and between the charged species and water are different for the 6101

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Figure 22. Temperature effect on calorimetric properties of (ionic liquid + apolar compound) binary mixtures at p = 0.1 MPa. (a) Molar enthalpy of mixing, ΔmixH; (b) partial molar excess enthalpies, H1̅ E and (c) H̅ 2E , as a function of composition, and (d) H̅ iE, ∞ for components in binary mixtures. Black and white bars correspond to H1̅ E,∞ and H̅ 2E,∞, respectively, for ▼, ([C1C4Im[TfO] + n-heptane) at T = 363.15 K;37 ▽, ([C1C4Im][TfO] + n-heptane) at T = 413.15 K;37 ■, ([C1C4Im][NTf2] + benzene) at T = 363.15 K;36 and □, ([C1C4Im][NTf2] + benzene) at T = 413.15 K.36 The lines represent data fittings using eqs 10, 12, and 13, for ΔmixH, H̅ 2E and H1̅ E , respectively. For all systems, ΔmixH were experimentally determined as reported in the corresponding literature. Subscripts 1 and 2 indicate the ionic liquid and the molecular compound, respectively.

*E-mail: [email protected].

different ionic liquids, making the structure-properties relationship difficult to formulate. Because a number of different groups have studied the energetics of mixing of ionic liquids with water, using a variety of calorimetric techniques, this is at present the best type of mixture to test the accuracy of the different experimental methods. Also, because a large number of cations and anions were studied with water, these mixtures are a good starting point to build test-sets for semiempirical prediction methods. As explained in section 4, the only mixtures for which it is possible to identify some trends on the energetic properties of mixing are the ones including imidazolium-based ionic liquids with alcohols. These trends point toward the explanation of the measured enthalpies of mixing and partial molar enthalpies of mixing by a balance between specific and dispersive interactions between the alcohols and the ionic liquids. When the nonpolar domains of the ionic liquids are important, the relative contribution of the interactions between the alcohols and the polar domains is less important. This fact appears in the important differences that are observed between the partial excess enthalpies of the components of the mixture, the enthalpies of mixing being slightly positive or largely negative for water but increasing for alcohols with increasing molecular size. Other polar (non-associate) compounds tend to mix exothermally with ionic liquids, the reported enthalpies of mixing being mainly negative. The analysis of the energetic properties of mixing of apolar compounds with ionic liquids is more complex as it depends on other chemical features of the molecular compound (aromaticity, presence of unsaturations, etc.). Relatively large positive and negative enthalpies of mixing are reported, often only in limited composition ranges, as these compounds are often partially miscible with ionic liquids.

Notes

The authors declare no competing financial interest. Biographies Ajda Podgoršek studied chemistry at the University of Ljubljana, Slovenia. In 2009 she completed her PhD thesis in organic chemistry under the guidance of Assist. Prof. Jernej Iskra at the Jozef Stefan Institute, Slovenia. In 2009 she joined the group of Prof. A. A. H. Pádua and Research Prof. M. F. Costa Gomes (Institute of Chemistry of Clermont-Ferrand, France) as a CNRS postdoctoral fellow. She worked in the field of molecular interactions and thermodynamics of ionic liquids, mainly concerning solvation of molecular solutes in these media. From 2012 she is employed as a researcher in Acies Bio, Ltd. (Ljubljana, Slovenia), where she is involved in improvement of synthesis of generic compounds and developing alternative synthesis of target compounds based on principles of green chemistry, including the use of alternative solvents. Johan Jacquemin received a Ph.D. in Physical Chemistry from the Blaise Pascal University of Clermont-Ferrand, France in 2006. He is currently senior lecturer in Chemical Engineering at the Queen’s University Belfast, in order to apply his physical chemistry science, and more precisely his knowledge in thermodynamic and in chemical engineering, for the study of novel materials, including electrolytes, solar cell materials, from the determination and the modeling of their fundamental properties through to the development of novel applications. He is interested in physical chemistry of pure components and their mixtures with other fluids and in particular on relationships between chemical structure and physical properties. More precisely his research area is focused on the development of original experimental apparatuses and physical models able to predict measured properties.

ASSOCIATED CONTENT

Agilio Padua is a professor of Physical Chemistry at Université Blaise Pascal in Clermont-Ferrand and a senior member of the Institut Universitaire de France. He heads the Thermodynamics and Molecular Interactions research team at the Institute of Chemistry of ClermontFerrand, a CNRS laboratory, and serves as editor of the Journal of Chemical Thermodynamics. Agilio Padua’s research aims at understanding the properties of new fluids and materials for a sustainable chemistry, from a knowledge of their molecular structure and interactions. His discipline is molecular thermodynamics, a synthesis of classical and statistical thermodynamics, physical chemistry and molecular physics, with applications to materials, devices and process engineering.

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemrev.5b00379. A complete database of the data on the enthalpy of mixing and on the partial molar excess enthalpy (XLSX)

AUTHOR INFORMATION Corresponding Authors

*E-mail: [email protected]. 6102

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NTf2−

Margarida Costa Gomes obtained her Chemical Engineering diploma and her PhD in the Instituto Superior Técnico in Lisbon Portugal. Before joining the French CNRS in 1998 she was a research associate at the Department of Chemical Engineering of Imperial College in London and a postdoctoral fellow at the Blaise Pascal University in ClermontFerrand, France. Margarida was awarded the CNRS Bronze Medal in 2003, passed her habilitation in 2004 and is a CNRS Research Professor since 2010. She is now responsible of the Ionic Liquids research group in the Institute of Chemistry of Clermont-Ferrand and participates in several French and European research networks on ionic liquids. Her research interests concern the physical chemistry of ionic liquids including their interactions with different solutes ranging from gases to polymers.

Glyc −, HOCH2COO− Lac −, CH3CH(HO)COO− C1SO3− TfO− C2SO3− HSO4− C1SO4− CF3SO4 − C2SO4− InCl4− FeCl4− GaCl4− Ala− Gly− H2O4P− CH3NO2 CH3CN IFC ITC

ACKNOWLEDGMENTS A.P. was financed by the Contrat d’Objectifs Partagés, CNRSUBP, Région Auvergne, France.

LIST OF ABBREVIATIONS C1CnIm+, n = 1, 2, 4, 5, 6, 8, 10 1-alkyl-3-methylimidazolium C1C1C4Im+ 1-butyl-2,3-dimethylimidazolium HOC2C2Im+ 1-(2-hydroxyethyl)-3-methylimidazolium b2mPy+ 1-butyl-2-methylpyridinium b3mPy+ 1-butyl-3-methylpyridinium b4mPy+ 1-butyl-4-methylpyridinium C1CnPyrro+, n = 4,6 N,N-alkyl-methylpyrrolidinium N1114+ butyl-trimethylammonium N2000+ ethylammonium N2226+ triethyl-hexylammonium N2228+ triethyl-octylammonium N22212+ triethyl-dodecylammonium N2‑O‑1000+ 2-methoxyethylammonium N3000+ propylammonium N4000+ butylammonium N4444+ tetrabutylammonium N8000+ octylammonium N9000+ nonylammonium Chol +, [HO(CH2)2N(CH3)3]+ 2-hydroxyethyl-trimethylammonium, cholinium 1,2,4-Triz+ 1H-1,2,4-triazolium C1C2Pip+ 1-methyl-1-ethylpiperidinium C1C4Pip+ 1-methyl-1-butylpiperidinium C1C6Pip+ 1-methyl-1-hexylpiperidinium C6Isoqui+ 2-hexylisoquinolium C8Isoqui+ 2-octylisoquinolium C1C2Morph+ 1-methyl-1-ethylmorpholinium Cl− chloride Br− bromide OAc− acetate CF3CO2− trifluoroacetate BF4− tetrafluoroborate hexafluorophosphate PF6− NO3− nitrate SCN− thiocyanate N(CN)2− dicyanamine DMP− dimethylphosphate DEP− diethylphosphate

Isoperibol Adiabatic Calvet UNIQUAC UNIFAC UNIFAC Do NRTL COSMO-RS ERAS

bis(trifluoromethylsulfonyl)imide 2-hydroxyethanoate, glycolate 2-hydroxypropanoate, lactate methanesulfonate trifluoromethanesulfonate, triflate ethanesulfonate hydrogen sulfate methylsulfate trifluoromethylsulfate ethylsulfate tetrachloroindate(III) tetrachloroferrate(III) tetrachlorogallate(III) alaninate glycinate dihydrogen phosphate nitromethane acetonitrile isothermal flow calorimetry isothermal titration calorimetry isoperibol solution calorimeter adiabatic solution calorimeter calvet condution calorimeter (batch or flow) universal quasi chemical universal functional activity coefficient UNIFAC Dortmunt non random two liquids conductor-like screening model for real solvent extended version of the real associated solution

List of Symbols

x1 and x2

mole fraction of the ionic liquid and molecular compound, respectively partial molar excess H1̅ E (kJ mol−1) and H̅ 2E (kJ mol−1) enthalpies of solvent and solute H1̅ E, ∞ (kJ mol−1) and H̅ 2E, ∞ (kJ mol−1) partial molar excess enthalpies at infinite dilution of solvent and solute ΔmixH (kJ mol−1) molar enthalpy of mixing ΔsolH (kJ mol−1) molar enthalpy of solution ΔsolH0 (kJ mol−1) standard molar enthalpy of solution ΔsolH∞ (kJ mol−1) molar enthalpy of solution at infinite dilution m(mol kg−1) molality

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(20) Ren, J.; Zhao, Z.; Zhang, X. Vapor Pressures, Excess Enthalpies, and Specific Heat Capacities of the Binary Working Pairs Containing the Ionic Liquid 1-Ethyl-3-methylimidazolium Dimethylphosphate. J. Chem. Thermodyn. 2011, 43, 576−583. (21) Constantinescu, D.; Schaber, K.; Agel, F.; Klingele, M. H.; Schubert, T. J. S. Viscosities, Vapor Pressures, and Excess Enthalpies of Choline Lactate + Water, Choline Glycolate + Water, and Choline Methanesulfonate + Water Systems. J. Chem. Eng. Data 2007, 52, 1280− 1285. (22) Curras, M. R.; Costa Gomes, M. F.; Husson, P.; Pádua, A. A. H.; Garcia, J. Calorimetric and Volumetric Study on Binary Mixtures 2,2,2Trifluoroethanol + (1-Butyl-3-methylimidazolium Tetrafluoroborate or 1-Ethyl-3-methylimidazolium Tetrafluoroborate). J. Chem. Eng. Data 2010, 55, 5504−5512. (23) Ficke, L. E.; Brennecke, J. F. Interactions of Ionic Liquids and Water. J. Phys. Chem. B 2010, 114, 10496−10501. (24) Ficke, L. E.; Novak, R. R.; Brennecke, J. F. Thermodynamic and Thermophysical Properties of Ionic Liquid + Water Systems. J. Chem. Eng. Data 2010, 55, 4946−4950. (25) Ficke, L. E.; Rodríguez, H.; Brennecke, J. F. Heat Capacities and Excess Enthalpies of 1-Ethyl-3-methylimidazolium-Based Ionic Liquids and Water. J. Chem. Eng. Data 2008, 53, 2112−2119. (26) García-Miaja, G.; Troncoso, J.; Romaní, L. Excess Enthalpy, Density, and Heat Capacity for Binary Systems of AlkylimidazoliumBased Ionic Liquids + Water. J. Chem. Thermodyn. 2009, 41, 161−166. (27) García-Miaja, G.; Troncoso, J.; Romaní, L. Excess Properties for Binary Systems Ionic Liquid + Ethanol: Experimental Results and Theoretical Description Using the ERAS Model. Fluid Phase Equilib. 2008, 274, 59−67. (28) García-Miaja, G.; Troncoso, J.; Romaní, L. Excess Molar Properties for Binary Systems of Alkylimidazolium-Based Ionic Liquids + Nitromethane. Experimental Results and ERAS-Model Calculations. J. Chem. Thermodyn. 2009, 41, 334−341. (29) Iglesias-Otero, M. A.; Troncoso, J.; Carballo, E.; Romaní, L. Densities and Excess Enthalpies for Ionic Liquids + Ethanol or + Nitromethane. J. Chem. Eng. Data 2008, 53, 1298−1301. (30) Navas, A.; Ortega, J.; Vreekamp, R.; Marrero, E.; Palomar, J. Experimental Thermodynamic Properties of 1-Butyl-2-methylpyridinium Tetrafluoroborate [b2mpy][BF4] with Water and with Alkan-1-ol and Their Interpretation with the COSMO-RS Methodology. Ind. Eng. Chem. Res. 2009, 48, 2678−2690. (31) Navia, P.; Troncoso, J.; Romaní, L. Excess Magnitudes for Ionic Liquid Binary Mixtures with a Common Ion. J. Chem. Eng. Data 2007, 52, 1369−1374. (32) Ortega, J.; Vreekamp, R.; Marrero, E.; Penco, E. Thermodynamic Properties of 1-Butyl-3-methylpyridinium Tetrafluoroborate and Its Mixtures with Water and Alkanols. J. Chem. Eng. Data 2007, 52, 2269− 2276. (33) Ortega, J.; Vreekamp, R.; Penco, E.; Marrero, E. Mixing Thermodynamic Properties of 1-Butyl-4-methylpyridinium Tetrafluoroborate [b4mpy][BF4] with Water and with an Alkan-1ol (Methanol to Pentanol). J. Chem. Thermodyn. 2008, 40, 1087−1094. (34) Rebelo, L. P. N.; Najdanovic-Visak, V.; Visak, Z. P.; Nunes da Ponte, M.; Szydlowski, J.; Cerdeiriña, C. A.; Troncoso, J.; Romaní, L.; Esperança, J. M. S. S.; Guedes, H. J. R.; de Sousa, H. C. A Detailed Thermodynamic Analysis of [C4mim][BF4] + Water as a case Study to Model Ionic Liquid Aqueous Solutions. Green Chem. 2004, 6, 369−381. (35) Vreekamp, R.; Castellano, D.; Palomar, J.; Ortega, J.; Espiau, F.; Fernández, L.; Penco, E. Thermodynamic Behavior of the Binaries 1Butylpyridinium Tetrafluoroborate with Water and Alkanols: Their Interpretation Using 1H NMR Spectroscopy and Quantum-Chemistry Calculations. J. Phys. Chem. B 2011, 115, 8763−8774. (36) Nebig, S.; Bölts, R.; Gmehling, J. Measurement of Vapor−Liquid Equilibria (VLE) and Excess Enthalpies (HE) of Binary Systems with 1Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide and Prediction of these Properties and γ∞ Using Modified UNIFAC (Dortmund). Fluid Phase Equilib. 2007, 258, 168−178. (37) Nebig, S.; Gmehling, J. Measurements of Different Thermodynamic Properties of Systems Containing Ionic Liquids and Correlation

REFERENCES (1) Pádua, A. A. H.; Costa Gomes, M. F.; Canongia Lopes, J. N. A. Molecular Solutes in Ionic Liquids: a Structural Perspective. Acc. Chem. Res. 2007, 40, 1087−1096. (2) Triolo, A.; Russina, O.; Bleif, H.-J.; Di Cola, E. Nanoscale Segregation in Room Temperature Ionic Liquids. J. Phys. Chem. B 2007, 111, 4641−4644. (3) Hansen, J. P.; McDonald, I. R. Theory of Simple Liquids, 2nd ed.; Academic Press: London, 1986. (4) Canongia Lopes, J. N. A.; Padua, A. A. H. Nanostructural Organization in Ionic Liquids. J. Phys. Chem. B 2006, 110, 3330−3335. (5) Canongia Lopes, J. N.; Costa Gomes, M. F.; Pádua, A. A. H. Nonpolar, Polar, and Associating Solutes in Ionic Liquids. J. Phys. Chem. B 2006, 110, 16816−16818. (6) Del Popolo, M. G.; Mullan, C. L.; Holbrey, J. D.; Hardacre, C.; Ballone, P. Ion Association in [bmim][PF6]/Naphthalene Mixtures: An Experimental and Computational Study. J. Am. Chem. Soc. 2008, 130, 7032−7041. (7) Zheng, W.; Mohammed, A.; Hines, L. G., Jr.; Xiao, D.; Matinez, O. J.; Bartsch, R. A.; Simon, S. L.; Russina, O.; Triolo, A.; Quitevis, E. L. Effect of Cation Symmetry on the Morphology and Physicochemical Properties of Imidazolium Ionic Liquids. J. Phys. Chem. B 2011, 115, 6572−6584. (8) Ionic Liquids in Synthesis; Welton, T.; Wassercheid, P., eds.; Wiley: Germany, 2003. (9) Santos, L. M. N. B. F.; Canongia Lopes, J. N.; Coutinho, J. A. P.; Esperança, J. M. S. S.; Gomes, L. R.; Marrucho, I. M.; Rebelo, L. P. N. Ionic Liquids: First Direct Determination of their Cohesive Energy. J. Am. Chem. Soc. 2007, 129, 284−285. (10) Shimizu, K.; Tariq, M.; Costa Gomes, M. F.; Rebelo, L. P. N.; Canongia Lopes, J. N. Assessing the Dispersive and Electrostatic Components of the Cohesive Energy of Ionic Liquids Using Molecular Dynamics Simulations and Molar Refraction Data. J. Phys. Chem. B 2010, 114, 5831−5834. (11) Jacquemin, J.; Ge, R.; Nancarrow, P.; Rooney, D. W.; Costa Gomes, M. F.; Pádua, A. A. H.; Hardacre, C. Prediction of Ionic Liquid Properties. I. Volumetric Properties as a Function of Temperature at 0.1 MPa. J. Chem. Eng. Data 2008, 53, 716−726. (12) Jacquemin, J.; Nancarrow, P.; Rooney, D. W.; Costa Gomes, M. F.; Husson, P.; Majer, V.; Pádua, A. A. H.; Hardacre, C. Prediction of Ionic Liquid Properties. II. Volumetric Properties as a Function of Temperature and Pressure. J. Chem. Eng. Data 2008, 53, 2133−2143. (13) Chirico, R. D.; Diky, V.; Magee, J. W.; Frenkel, M.; Marsh, K. N. Thermodynamic and Thermophysical Properties of the Reference Ionic Liquid: 1-Hexyl-3-methylimidazolium Bis[(trifluoromethyl)sulfonyl]amide (Including Mixtures). Part 2. Critical Evaluation and Recommended Property Values (IUPAC Technical Report). Pure Appl. Chem. 2009, 81, 791−828. (14) Kato, H.; Miki, K.; Mukai, T.; Nishikawa, K.; Koga, Y. Hydrophobicity/Hydrophilicity of 1-Butyl-2,3-dimethyl and 1-Ethyl-3methylimodazolium Ions: Toward Characterization of Room Temperature Ionic Liquids. J. Phys. Chem. B 2009, 113, 14754−14760. (15) Keil, P.; Konig, A. Enthalpies of Solution of 1-Ethyl-3-methylimidazolium Chloride and Aluminum Chloride in Molten Chloroaluminate Ionic Liquids. Thermochim. Acta 2011, 524, 202−204. (16) Van Ness, H. C.; Abbott, M. M. Classical Thermodynamics of Nonelectrolyte Solutions: With Applications to Phase Equilibria; McGrawHill: New York, 1982; Section 5−7. (17) Andriola, A.; Singh, K.; Lewis, J.; Yu, L. Conductivity, Viscosity, and Dissolution Enthalpy of LiNTF2 in Ionic Liquid BMINTF2. J. Phys. Chem. B 2010, 114, 11709−11714. (18) Archer, D. G.; Widegren, J. A.; Kirklin, D. R.; Magee, J. W. Enthalpy of Solution of 1-Octyl-3-methylimidazolium Tetrafluoroborate in Water and in Aqueous Sodium Fluoride. J. Chem. Eng. Data 2005, 50, 1484−1491. (19) He, Z.; Zhao, Z.; Zhang, X.; Feng, H. Thermodynamic Properties of New Heat Pump Working Pairs: 1,3-Dimethylimidazolium Dimethylphosphate and Water, Ethanol and Methanol. Fluid Phase Equilib. 2010, 298, 83−91. 6104

DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106

Chemical Reviews

Review

of These Properties Using Modified UNIFAC (Dortmund). Fluid Phase Equilib. 2010, 294, 206−212. (38) Nebig, S.; Gmehling, J. Prediction of Phase Equilibria and Excess Properties for Systems with Ionic Liquids Using Modified UNIFAC: Typical Results and Present Status of the Modified UNIFAC Matrix for Ionic Liquids. Fluid Phase Equilib. 2011, 302, 220−225. (39) Nebig, S.; Liebert, V.; Gmehling, J. Measurement and Prediction of Activity Coefficients at Infinite Dilution (γ∞), Vapor−Liquid Equilibria (VLE) and Excess Enthalpies (HE) of Binary Systems with 1,1-Dialkyl-pyrrolidinium Bis(trifluoromethylsulfonyl)imide Using Mod. UNIFAC (Dortmund). Fluid Phase Equilib. 2009, 277, 61−67. (40) Liebert, V.; Nebig, S.; Gmehling, J. Experimental and Predicted Phase Equilibria and Excess Properties for Systems with Ionic Liquids. Fluid Phase Equilib. 2008, 268, 14−20. (41) Kato, R.; Krummen, M.; Gmehling, J. Measurement and Correlation of Vapor−Liquid Equilibria and Excess Enthalpies of Binary Systems Containing Ionic Liquids and Hydrocarbons. Fluid Phase Equilib. 2004, 224, 47−54. (42) Porcedda, S.; Marongiu, B.; Schirru, M.; Falconieri, D.; Piras, A. Excess Enthalpy and Excess Volume for Binary Systems of Two Ionic Liquids + Water. J. Therm. Anal. Calorim. 2011, 103, 29−33. (43) Leskiv, M.; Bernardes, C. E. S.; Minas da Piedade, M. E.; Canongia Lopes, J. N. Energetics of Aqueous Solutions of the Ionic Liquid 1-Ethyl3-methylimidazolium Ethylsulfate. J. Phys. Chem. B 2010, 114, 13179− 13188. (44) Balantseva, E.; Lehmann, J. K.; Heintz, A. Enthalpies of Solution of Organic Solutes in the Ionic Liquids [Me3BuN][NTf2] and [EMIM][EtSO4]. Z. Phys. Chem. 2006, 220, 1499−1550. (45) Campbell, P. S.; Podgoršek, A.; Gutel, T.; Santini, C. C.; Pádua, A. A. H.; Costa Gomes, M. F.; Bayard, F.; Fenet, B.; Chauvin, Y. How do Physical−Chemical Parameters Influence the Catalytic Hydrogenation of 1,3-Cyclohexadiene in Ionic Liquids? J. Phys. Chem. B 2010, 114, 8156−8165. (46) Deng, Y.; Husson, P.; Jacquemin, J.; Youngs, T. G. A.; Kett, V. L.; Hardacre, C.; Costa Gomes, M. F. Volumetric Properties and Enthalpies of Solution of Alcohols CkH2k+1OH (k = 1, 2, 6) in 1-Methyl-3alkylimidazolium Bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} Ionic Liquids. J. Chem. Thermodyn. 2011, 43, 1708− 1718. (47) Heintz, A.; Verevkin, S. P.; Lehmann, J. K.; Vasiltsova, T. V.; Ondo, D. Activity Coefficients at Infinite Dilution and Enthalpies of Solution of Methanol, 1-Butanol, and 1-Hexanol in 1-Hexyl-3-methylimidazolium Bis(trifluoromethyl-sulfonyl) Imide. J. Chem. Thermodyn. 2007, 39, 268−274. (48) Marczak, W.; Verevkin, S. P.; Heintz, A. Enthalpies of Solution of Organic Solutes in the Ionic Liquid 1-Methyl-3-ethyl-imidazolium Bis(trifluoromethyl-sulfonyl) Amide. J. Solution Chem. 2003, 32, 519−526. (49) Li, S.; Yan, W.; Dong, H. Determination of Partial Molar Excess Enthalpies at Infinite Dilution for the Systems Four Alcohols + [bmim]PF6 at Different Temperatures by Isothermal Titration Calorimeter. Fluid Phase Equilib. 2007, 261, 444−448. (50) Podgoršek, A.; Pensado, A. S.; Santini, C. C.; Costa Gomes, M. F.; Pádua, A. A. H. Interaction Energies of Ionic Liquids with Metallic Nanoparticles: Solvation and Stabilization Effects. J. Phys. Chem. C 2013, 117, 3537−3547. (51) Rai, G.; Kumar, A. An Enthalpic Approach to Delineate the Interactions of Cations of Imidazolium-Based Ionic Liquids with Molecular Solvents. Phys. Chem. Chem. Phys. 2011, 13, 14715−14722. (52) Guan, W.; Li, L.; Ma, X.-X.; Tong, J.; Fang, D.-W.; Yang, J.-Z. Study on the Enthalpy of Solution and Enthalpy of Dilution for the Ionic Liquid [C3mim][Val] (1-Propyl-3-methylimidazolium Valine). J. Chem. Thermodyn. 2012, 47, 209−212. (53) Fang, D.-W.; Sun, Y.-C.; Wang, Z.-W. Solution Enthalpies of Ionic Liquid 1-Hexyl-3-methylimidazolium Chloride. J. Chem. Eng. Data 2008, 53, 259−261. (54) Guan, W.; Li, L.; Wang, H.; Tong, J.; Yang, J.-Z. Studies on Thermochemical Properties of Ionic Liquids Based on Transition Metal. J. Therm. Anal. Calorim. 2008, 94, 507−510.

(55) Guan, W.; Liu, L.; Wang, C.; Yang, J. Molal Enthalpy of Solution of Ionic Liquid [C2mim][GaCl4]. Chin. J. Chem. 2009, 27, 713−716. (56) Guan, W.; Wang, H.; Li, L.; Zhang, Q.-G.; Yang, J.-Z. Enthalpy of Solution of the Ionic Liquid BMIBF4 in Water. Thermochim. Acta 2005, 437, 196−197. (57) Guan, W.; Xue, W.-F.; Li, N.; Tong, J. Enthalpy of Solution of Amino Acid Ionic Liquid 1-Butyl-3-methylimidazolium Glycine. J. Chem. Eng. Data 2008, 53, 1401−1403. (58) Guan, W.; Xue, W.-F.; Tong, J.; Wang, C.-X.; Yang, J.-Z. The Enthalpy of Solution of the Alanine-Based Ionic Liquid [C4mim][Ala]. J. Solution Chem. 2009, 38, 1463−1469. (59) Guan, W.; Yang, J.-Z.; Li, L.; Wang, H.; Zhang, Q.-G. ThermoChemical Properties of Aqueous Solution Containing Ionic Liquids: 1. The Heat of Reaction Mixed 1-Methyl-3-butylimidazolium Chloride with InCl3. Fluid Phase Equilib. 2006, 239, 161−165. (60) Zhang, Z.-F.; Li, J.-G.; Zhang, Q.-G.; Guan, W.; Yang, J.-Z. Enthalpy of Solution of Amino Acid Ionic Liquid 1-Ethyl-3methylimidazolium Ammonioacetate. J. Chem. Eng. Data 2008, 53, 1196−1198. (61) Yang, J.-Z.; Guan, W.; Tong, J.; Wang, H.; Li, L. Studies of Thermochemical Properties of a New Ionic Liquid Prepared by Mixing 1-Methyl-3-Pentylimidazolium Chloride with InCl3. J. Solution Chem. 2006, 35, 845−852. (62) Yang, J.-Z.; Zhang, Z.-H.; Fang, D.-W.; Li, J.-G.; Guan, W.; Tong, J. Studies on Enthalpy of Solution for Ionic Liquid: The System of 1Methyl-3-ethylimidazolium Tetrafluoroborate (EMIBF4). Fluid Phase Equilib. 2006, 247, 80−83. (63) Waliszewski, D.; Stępniak, I.; Piekarski, H.; Lewandowski, A. Heat Capacities of Ionic Liquids and Their Heats of Solution in Molecular Liquids. Thermochim. Acta 2005, 433, 149−152. (64) Principles of Thermal Analysis and Calorimetry; The Royal Society of Chemistry, 2002. (65) The Japan Society of Calorimetry and Thermal Analysis. Comprehensive Handbook of Calorimetry and Thermal Analysis; John Wiley & Sons, Ltd, Weinheim, 2004. (66) Experimental Thermodynamics: Solution Calorimetry, IUPAC Commission on Thermodynamics; Blackwell Scientific Publications: Oxford, 1994. (67) Wilson, R. J. Calorimetry. In Principles of Thermal Analysis and Calorimetry; Haines, P. J., Ed.; The Royal Society of Chemistry, Cambridge, 2002; pp 129−165. (68) Archer, D. G.; Kirklin, D. R. Enthalpies of Solution of Sodium Chloride and Potassium Sulfate in Water. Thermodynamic Properties of the Potassium Sulfate + Water System. J. Chem. Eng. Data 2002, 47, 33− 46. (69) Yu, H.-G.; Liu, Y.; Tan, Z.-C.; Dong, J.-X.; Zou, T.-J.; Huang, X.M.; Qu, S.-S. A Solution-Reaction Isoperibol Calorimeter and Standard Molar Enthalpies of Formation of Ln(hq)2Ac (Ln = La, Pr). Thermochim. Acta 2003, 401, 217−224. (70) Almantariotis, D.; Fandiño, O.; Coxam, J.-Y.; Costa Gomes, M. F. Direct Measurement of the Heat of Solution and Solubility of Carbon Dioxide in 1-Hexyl-3-methylimidazolium Bis[trifluoromethylsulfonyl]amide and 1-Octyl-3-methylimidazolium Bis[trifluoromethylsulfonyl]amide. Int. J. Greenhouse Gas Control 2012, 10, 329−340. (71) Monk, P.; Wadsö, I.; Karvonen, P.; Virtanen, A. I.; Paasivirta, J. A Flow Micro Reaction Calorimeter. Acta Chem. Scand. 1968, 22, 1842− 1852. (72) Matteoli, E.; Lepori, L. Determination of the Excess Enthalpy of Binary Mixtures from the Measurements of the Heat of Solution of the Components: Application to the Perfluorohexane + Hexane Mixture. Fluid Phase Equilib. 2000, 174, 115−131. (73) Rai, G.; Kumar, A. Probing Thermal Interactions of Ionic Liquids with Dimethyl Sulfoxide. ChemPhysChem 2012, 13, 1927−1933. (74) Redlich, O.; Kister, A. T. Algebraic Representation of Thermodynamic Properties and the Classification of Solutions. Ind. Eng. Chem. 1948, 40, 345−348. (75) Abrams, D. S.; Prausnitz, J. M. Statistical Thermodynamics of Liquid Mixtures: A New Expression for the Excess Gibbs Energy of Partly or Completely Miscible Systems. AIChE J. 1975, 21, 116−128. 6105

DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106

Chemical Reviews

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(76) Lohmann, J.; Joh, R.; Gmehling, J. From UNIFAC to Modified UNIFAC (Dortmund). Ind. Eng. Chem. Res. 2001, 40, 957−964. (77) Renon, H.; Prausnitz, J. M. Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures. AIChE J. 1968, 14, 135− 144. (78) Wilson, G. M. Vapor-Liquid Equilibrium. XI. A New Expression for the Excess Free Energy of Mixing. J. Am. Chem. Soc. 1964, 86, 127− 130. (79) Heintz, A.; Dolch, E.; Lichtenthaler, R. N. New Experimental VLE-Data for Alkanol/Alkane Mixtures and Their Description by an Extended Real Association (ERAS) Model. Fluid Phase Equilib. 1986, 27, 61−79. (80) Klamt, A.; Schüürmann, G. COSMO: a New Approach to Dielectric Screening in Solvents with Explicit Expressions for the Screening Energy and its Gradient. J. Chem. Soc., Perkin Trans. 2 1993, 2, 799−805. (81) Bhagour, S.; Solanki, S.; Hooda, N.; Sharma, D.; Sharma, V. K. Thermodynamic Properties of Binary Mixtures of the Ionic Liquid [emim][BF4] with Acetone and Dimethylsulfoxide. J. Chem. Thermodyn. 2013, 60, 76−86. (82) Solanki, S.; Hooda, N.; Sharma, V. K. Topological Investigations of Binary Mixtures Containing Ionic Liquid 1-Ethyl-3-methylimidazolium Tetrafluoroborate and Pyridine or Isomeric Picolines. J. Chem. Thermodyn. 2013, 56, 123−135. (83) Sharma, D.; Bhagour, S.; Sharma, V. K. Thermodynamic and Topological Studies of 1-Ethyl-3-methylimidazolium Tetrafluoroborate + Pyrrolidin-2-one and 1-Methyl-pyrrolidin-2-one Mixtures. J. Chem. Eng. Data 2012, 57, 3488−3497. (84) Królikowska, M.; Paduszyński, K.; Zawadzki, M. Measurements, Correlations, and Predictions of Thermodynamic Properties of NOctylisoquinolinium Thiocyanate Ionic Liquid and Its Aqueous Solutions. J. Chem. Eng. Data 2013, 58, 285−293. (85) Królikowska, M.; Paduszyński, K.; Hofman, T.; Antonowicz, J. Heat Capacities and Excess Enthalpies of the (N-Hexylisoquinolinium Thiocyanate Ionic Liquid + Water) Binary Systems. J. Chem. Thermodyn. 2012, 55, 144−150. (86) Ma, X.-X.; Zhang, Q.-B.; Wei, J.; Pan, Y.; Guan, W.; Yang, J.-Z. Study on Enthalpy and Molar Heat Capacity of Solution for Ionic Liquid [C3mim][OAc] (1-Propyl-3-methylimidazolium Acetate). J. Chem. Thermodyn. 2013, 65, 91−94. (87) Ma, X.-X.; Li, L.; Wei, J.; Duan, W.-B.; Yang, J.-Z.; Guan, W. Study on Enthalpy and Molar Heat Capacity of Solution for the Ionic Liquid [C2mim][OAc] (1-Ethyl-3-methylimidazolium acetate). J. Chem. Eng. Data 2012, 57, 3171−3175. (88) Stark, A.; Zidell, A. W.; Russo, J. W.; Hoffmann, M. M. Composition Dependent Physicochemical Property Data for the Binary System Water and the Ionic Liquid 1-Butyl-3-methylimidazolium Methanesulfonate ([C4mim][MeSO3]). J. Chem. Eng. Data 2012, 57, 3330−3339. (89) Kustov, A. V.; Smirnova, N. L.; Antonova, O. A. Enthalpies and Heat Capacities of Interaction of Tetraalkylammonium Bromides with Hexamethylphosphoric Triamide in Water, Methanol and Ethylene Glycol: The Comparative Analysis of Aqueous and Non-Aqueous Systems. Thermochim. Acta 2012, 544, 84−88. (90) Kiselev, V. D.; Kashaeva, H. A.; Shakirova, I. I.; Potapova, L. N.; Konovalov, A. I. Solvent Effect on the Enthalpy of Solution and Partial Molar Volume of the Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate. J. Solution Chem. 2012, 41, 1375−1387. (91) Zhang, L.-J.; Tan, Z.-C.; Chen, J.-T.; Di, Y.-Y. Crystal Structures and Thermochemical Properties of n-Nonylammonium Dihydrogen Phosphate C9H19NH3·H2PO4(s) and n-Octylammonium Dihydrogen Phosphate C8H17NH3·H2PO4(s). J. Chem. Eng. Data 2011, 56, 4491− 4498. (92) Xue, L.; Zhao, F.; Xing, X.; Zhou, Z.; Wang, K.; Gao, H.; Yi, J.; Xu, S.; Hu, R. Dissolution Properties of 1,2,4-Triazole Nitrate in N-Methyl Pyrrolidone. J. Chem. Eng. Data 2011, 56, 259−262. (93) Królikowska, M.; Zawadzki, M.; Królikowski, M. Physicochemical and Thermodynamic Study on Aqueous Solutions of Dicyanamide − Based Ionic Liquids. J. Chem. Thermodyn. 2014, 70, 127−137.

(94) Machanová, K.; Troncoso, J.; Jacquemin, J.; Bendová, M. Excess Molar Volumes and Excess Molar Enthalpies in Binary Systems N-Alkyltriethylammonium Bis(trifluoromethylsulfonyl)imide + Methanol. Fluid Phase Equilib. 2014, 363, 156−166. (95) Usula, M.; Matteoli, E.; Leonelli, F.; Mocci, F.; Marincola, F. C.; Gontrani, L.; Porcedda, S. Thermo-Physical Properties of AmmoniumBased Ionic Liquid + N-Methyl-2-pyrrolidone Mixtures at 298.15 K. Fluid Phase Equilib. 2014, 383, 49−54. (96) Paduszyński, K.; Królikowski, M.; Domańska, U. Excess Enthalpies of Mixing of Piperidinium Ionic Liquids with Short-Chain Alcohols: Measurements and PC-SAFT Modeling. J. Phys. Chem. B 2013, 117, 3884−3891. (97) Królikowska, M.; Paduszyński, K.; Królikowski, M.; Lipiński, P.; Antonowicz, J. Vapor−Liquid Phase Equilibria and Excess Thermal Properties of Binary Mixtures of Ethylsulfate-Based Ionic Liquids with Water: New Experimental Data, Correlations, and Predictions. Ind. Eng. Chem. Res. 2014, 53, 18316−18325. (98) Gonzalez-Miquel, M.; Massel, M.; DeSilva, A.; Palomar, J.; Rodriguez, F.; Brennecke, J. F. Excess Enthalpy of Monoethanolamine + Ionic Liquid Mixtures: How Good are COSMO-RS Predictions? J. Phys. Chem. B 2014, 118, 11512−11522. (99) Domańska, U.; Papis, P.; Szydłowski, J.; Królikowska, M.; Królikowski, M. Excess Enthalpies of Mixing, Effect of Temperature and Composition on the Density, and Viscosity and Thermodynamic Properties of Binary Systems of {Ammonium-Based Ionic Liquid + Alkanediol}. J. Phys. Chem. B 2014, 118, 12692−12705. (100) Massel, M.; Revelli, A.-L.; Paharik, E.; Rauh, M.; Mark, L. O.; Brennecke, J. F. Phase Equilibrium, Excess Enthalpies, and Densities of Binary Mixtures of Trimethylbutylammonium Bis(trifluoromethylsulfonyl)imide with Ethanol, 1-Propanol, and Dimethylformamide. J. Chem. Eng. Data 2015, 60, 65−73. (101) Paduszyński, K.; Lukoshko, E. V.; Królikowski, M.; Domańska, U.; Szydłowski, J. Thermodynamic Study of Binary Mixtures of 1-Butyl1-methylpyrrolidinium Dicyanamide Ionic Liquid with Molecular Solvents: New Experimental Data and Modeling with PC-SAFT Equation of State. J. Phys. Chem. B 2015, 119, 543−551.

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DOI: 10.1021/acs.chemrev.5b00379 Chem. Rev. 2016, 116, 6075−6106