Volumetric Properties of Binary Mixtures of 1-Butyl-3

Article pubs.acs.org/jced

Volumetric Properties of Binary Mixtures of 1‑Butyl-3Methylimidazolium Tris(pentafluoroethyl)trifluorophosphate with N‑Methylformamide, N‑Ethylformamide, N,N‑Dimethylformamide, N,N‑Dibutylformamide, and N,N‑Dimethylacetamide from (293.15 to 323.15) K Milan Vraneš, Aleksandar Tot, Nebojša Zec, Snežana Papović, and Slobodan Gadžurić* Faculty of Science, Department of Chemistry, Biochemistry and Environmental Protection, University of Novi Sad, Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia S Supporting Information *

ABSTRACT: Volumetric properties of 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([BMIM][FAP]) ionic liquid binary mixtures with two protic amides: N-methyl-formamide (NMF) and N-ethylformamide (NEF), and three aprotic amides: N,N-dimethylformamide (DMF), N,Ndibutylformamide (DBF), and N,N-dimethylacetamide (DMA), are calculated from the experimental densities and reported in the temperature range from (293.15 to 323.15) K and at atmospheric pressure (0.1 MPa) over the whole composition range. The excess molar volumes have positive values in the whole concentration range, with maximum values in the range between 0.3 and 0.6 ionic liquid mole fraction. Higher values of excess molar volumes are observed in the mixtures containing aprotic amides (DMF, DBF, DMA). Also, the molar volume of binary mixtures, the apparent molar volumes, the partial molar volumes of the components, and the partial molar volumes of the components at infinite dilution are calculated. All of the results are compared with those obtained for pyrrolidinium-based ionic liquids with the same anion in the mixtures with the selected amides.

1. INTRODUCTION In the past decade, increasing attention has been paid to the use of ionic liquids (ILs), which are an alternative solvent to volatile organic compounds (VOCs). Due to their unique physical and chemical properties, such as high thermal1 and electrochemical stability,2 a low vapor pressure,3 nonflammability,4 and biodegradability,5 the ionic liquids are widely used as a new solvent in catalysis,6 synthesis,7,8 and separation processes.9,10 One of the most studied ionic liquids are those with a 1,3substituted imidazolium cation, because of their favorable physical and chemical properties.11−14 In the combination with a highly fluorinated anion such as tris(pentafluoroethyl)trifluorophosphate, [FAP], these ionic liquids achieve an excellent air and hydrolytic stability. In contrast to the hydrolytic instability of hexafluorophosphate anion, [PF6],15−17 ionic liquids containing [FAP] anion are extremely hydrophobic16,18 and have a high heat capacity,19 a wide electrochemical window,20 a high thermal stability,21 and a very low vapor pressure.22,23 It has been found that a wide range of hydrophobic ionic liquids have the ability to encourage self-association of the amphiphiles.24 There are a number of nonaqueous polar molecular solvents, which are known to be self-associating amphiphiles.25 Among them are the group of the lower amides: © 2014 American Chemical Society

N-methylformamide (NMF), N,N-dimethylformamide (DMF), N-ethylformamide (NEF), N,N-dibutylformamide (DBF), and N,N-dimethylacetamide (DMA). In this paper the volumetric properties of the binary mixtures of 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ionic liquid ([BMIM][FAP]) with selected amides, two protic (NMF and NEF) and three aprotic (DMF, DBF, and DMA), were investigated. It is known that the [FAP] anion because of the lack of the coordination possibility emphasizes the features and properties of the cation. Therefore, obtained volumetric data are compared with the results previously published for the mixture of investigated amides with pyrrolidinium-based ionic liquid with the [FAP] anion ([BMPYR][FAP]).26 The influence of the cation on the volumetric properties is also discussed.

2. EXPERIMENTAL SECTION All used amides were purified by distillation, and the middle fraction was collected. After that, amides were dried for 15 h Received: April 15, 2014 Accepted: September 23, 2014 Published: October 3, 2014 3372

dx.doi.org/10.1021/je5002945 | J. Chem. Eng. Data 2014, 59, 3372−3379

Journal of Chemical & Engineering Data

Article

under vacuum and kept in the sealed dark bottles over the molecular sieves 4 Å for 3 weeks prior to their use. The ionic liquid [BMIM][FAP] was dried for several days under reduced pressure to remove all traces of water. The water content was less 1·10−4 mass fraction, as determined by Karl Fisher titration. The summary of the provenance and purity of the chemicals is given in Table 1.

Table 2. Experimental and Literature Values of Densities, d, of the Pure Liquids at the Specified Temperatures and at Atmospheric Pressure (0.1 MPa)a 10−3·d/(kg·m−3) component [BMIM] [FAP]

Table 1. Provenance and Purity of the Samples chemical name

provenance

1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate N-methylformamide N,N-dimethylformamide N-ethylformamide N,N-dibutylformamide N,N-dimethylacetamide

mass fraction purity

Merck

≥ 0.99

Sigma-Aldrich J.T. Baker Sigma-Aldrich Sigma-Aldrich Merck

≥ ≥ ≥ ≥ ≥

NMF

0.99 0.998 0.99 0.99 0.99

Binary mixtures containing [BMIM][FAP] and studied amides covering the whole composition range were prepared by measuring appropriate amount of the components on a Denver analytical balance. The combined experimental uncertainty (k = 2) of mass fraction was less than 5·10−5. The vibrating tube densimeter, Rudolph Research Analytical DDM 2911, was used for density measurements. The apparatus and the measurement procedure were described in our previous publication.26 Repeated experimental measurements showed reproducibility within 0.001 %, and an average value was shown in this paper. The combined experimental uncertainty (k = 2) of determining the density is less than 2·10−2 kg·m−3.

DMF

NEF

3. RESULTS AND DISCUSSION Densities of pure components and ([BMIM][FAP] + amides) mixtures were measured over the whole composition range at selected temperatures from (293.15 to 323.15) K. The results are tabulated in Tables 2 and 3. All obtained densities for the investigated mixtures (d) decrease with the increase of temperature, as expected. Also the values of density are higher in the ionic liquid rich region. The excess molar volume VE was calculated from the experimental density using the following equation: ⎛1 ⎛1 1⎞ 1⎞ V E = x1M1⎜ − ⎟ + x 2M 2⎜ − ⎟ d1 ⎠ d2 ⎠ ⎝d ⎝d

DBF

DMA

(1)

where M is the molar mass; pure components [BMIM][FAP] and amide are assigned with subscripts 1 and 2, respectively. The values of the excess molar volumes are fitted using a Redlich−Kister type equation:50 n i

E

V = x1x 2 ∑ Ai (2x1 − 1) i=0

(2)

T/K

this work

293.15

1.63116

1.63129 (290.30 K)23

298.15 303.15 308.15 313.15 318.15 323.15 293.15 298.15

1.62532 1.61953 1.61368 1.60786 1.60195 1.59603 1.00335 0.99891

1.62589 1.61899 1.61378 1.60791 1.60166 1.59695

303.15 308.15 313.15 318.15 323.15 293.15

0.99449 0.99001 0.98547 0.98088 0.97624 0.94872

298.15

0.94386

303.15

0.93900

308.15 313.15

0.93408 0.92913

318.15 323.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15 293.15 298.15

0.92406 0.91896 0.95159 0.94748 0.94329 0.93904 0.93478 0.93045 0.92606 0.87905 0.87512 0.87117 0.86715 0.86311 0.85901 0.85482 0.94092 0.93630

303.15 308.15

0.93162 0.92689

313.15 318.15 323.15

0.92209 0.91723 0.91223

reference

(298.29 (302.94 (308.03 (313.32 (318.20 (322.75

K)23 K)23 K)23 K)23 K)23 K)23

0.99858;27 0.9988;28 0.99929;29 0.9988930 0.994831 0.990531 0.986131 0.981831 0.9491;32 0.948051;33 0.9491;34 0.9485835 0.9446;32 0.942915;33 0.9449;34 0.9445;36 0.94406;29 0.9438330 0.9401;32 0.9402;34 0.93946;35 0.9398;36 0.939437 0.9357;32 0.9355;34 0.9351;36 0.934237 0.9312;32 0.9307;34 0.93012;35 0.9302;36 0.930137 0.9267;32 0.9259;34 0.925337 0.92055;35 0.920137 0.955238 0.944739 0.936439

0.87540

0.94155;41 0.93982442 0.93634;41 0.9364;43 0.93654;44 0.93617;45 0.93615;46 0.936382;47 0.936337;48 0.9363149 0.9316641 0.92704;41 0.926297;42 0.92714;47 0.9270849 0.917216;42 0.917863;47 0.91782;49

The combined experimental uncertainties (k = 2) are u(d) = 2·10−2 kg·m−3, u(x) = 5·10−5, and u(T) = 0.01 K. a

The results are given in Table S1 in the Supporting Information and graphically presented in Figure 1. The values of the adjustable parameters Ai were calculated by using the method of least-squares. These coefficients are given in Table S2 as the Supporting Information, together with the standard deviations of the fit. From Figure 1, it can be seen that in all investigated systems the excess molar volumes have a positive values in the whole

concentration range, with maximum values in the range 0.3 ≤ x1 ≤ 0.6. Positive values of VE indicate that the interactions within the pure components are stronger than the interactions between the ions and amides after their mixing. Mixtures containing aprotic amides (DMF, DBF, DMA) show higher 3373



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Table 3. Experimental Density (d) of the Studied Mixtures at Different Temperatures and Compositions at Atmospheric Pressure (0.1 MPa)a 10−3·d/(kg·m−3) T/K x1

293.15

298.15

0.0177 0.0496 0.0664 0.1003 0.1495 0.2000 0.2968 0.4150 0.4958 0.5497 0.6043 0.6816 0.8148 0.9028

1.06368 1.15062 1.18802 1.25067 1.32015 1.37381 1.44668 1.50535 1.53452 1.55047 1.56453 1.58175 1.60562 1.61856

1.05908 1.14591 1.18315 1.24548 1.31468 1.36820 1.44098 1.49953 1.52869 1.54463 1.55868 1.57593 1.59977 1.61273

0.0182 0.0664 0.0998 0.2010 0.3017 0.4016 0.5024 0.5970 0.6927 0.7560 0.7924 0.8499 0.8946

1.00050 1.11133 1.17162 1.30475 1.39257 1.45503 1.50236 1.53691 1.56542 1.58139 1.58958 1.60204 1.61097

0.99554 1.10611 1.16627 1.29919 1.38688 1.44928 1.49665 1.53106 1.55958 1.57558 1.58378 1.59625 1.60515

0.0346 0.0702 0.1019 0.2005 0.3013 0.4019 0.4936 0.6054 0.7017 0.7892 0.8837 0.9417

1.04796 1.12660 1.18375 1.31244 1.39864 1.45970 1.50192 1.54177 1.56908 1.58979 1.60926 1.62024

1.04351 1.12175 1.17870 1.30703 1.39322 1.45414 1.49621 1.53592 1.56325 1.58401 1.60353 1.61453

0.0344 0.0694 0.0908 0.1509 0.1983 0.3053 0.4013 0.5001 0.5949 0.7025 0.8049 0.9051 0.9470

0.92873 0.97575 1.00284 1.07317 1.12357 1.22438 1.30246 1.37310 1.43303 1.49316 1.54402 1.58961 1.60782

0.92465 0.97159 0.99856 1.06874 1.11898 1.21955 1.29741 1.36789 1.42771 1.48766 1.53837 1.58383 1.60208

303.15

308.15

[BMIM][FAP] (1) + NMF (2) 1.05445 1.04977 1.14096 1.13595 1.17805 1.17290 1.24025 1.23494 1.30920 1.30367 1.36264 1.35698 1.43524 1.42945 1.49367 1.48783 1.52288 1.51702 1.53876 1.53285 1.55285 1.54699 1.57009 1.56423 1.59395 1.58814 1.60693 1.60110 [BMIM][FAP] (1) + DMF (2) 0.99059 0.98556 1.10090 1.09562 1.16094 1.15553 1.29361 1.28797 1.38121 1.37546 1.44355 1.43774 1.49089 1.48503 1.52527 1.51949 1.55377 1.54798 1.56977 1.56395 1.57798 1.57218 1.59047 1.58467 1.59934 1.59356 [BMIM][FAP] (1) + NEF (2) 1.03906 1.03461 1.11703 1.11231 1.17382 1.16888 1.30167 1.29629 1.38764 1.38200 1.44847 1.44276 1.49049 1.48476 1.53027 1.52446 1.55756 1.55174 1.57831 1.57248 1.59777 1.59190 1.60873 1.60285 [BMIM][FAP] (1) + DBF (2) 0.92052 0.91647 0.96739 0.96319 0.99435 0.99005 1.06432 1.05986 1.11441 1.10982 1.21470 1.20982 1.29236 1.28730 1.36275 1.35746 1.42243 1.41697 1.48231 1.47666 1.53292 1.52713 1.57821 1.57238 1.59637 1.59048

3374

313.15

318.15

323.15

1.04505 1.13098 1.16779 1.22960 1.29811 1.35130 1.42365 1.48195 1.51112 1.52694 1.54111 1.55834 1.58226 1.59523

1.04026 1.12588 1.16265 1.22421 1.29253 1.34556 1.41778 1.47601 1.50515 1.52106 1.53517 1.55244 1.57638 1.58936

1.03540 1.12076 1.15738 1.21875 1.28699 1.33977 1.41184 1.47004 1.49920 1.51513 1.52919 1.54655 1.57042 1.58343

0.98046 1.09029 1.15008 1.28233 1.36970 1.43191 1.47922 1.51369 1.54216 1.55813 1.56637 1.57884 1.58774

0.97529 1.08487 1.14455 1.27660 1.36386 1.42604 1.47331 1.50783 1.53632 1.55234 1.56048 1.57297 1.58185

0.97002 1.07938 1.13897 1.27082 1.35798 1.42014 1.46738 1.50192 1.53050 1.54643 1.55462 1.56702 1.57591

1.03007 1.10755 1.16392 1.29093 1.37636 1.43705 1.47901 1.51866 1.54592 1.56659 1.58602 1.59697

1.02551 1.10279 1.15898 1.28566 1.37082 1.43135 1.47323 1.51283 1.54003 1.56070 1.58013 1.59109

1.02095 1.09801 1.15406 1.28050 1.36536 1.42568 1.46747 1.50700 1.53414 1.55481 1.57424 1.58521

0.91226 0.95886 0.98569 1.05532 1.10523 1.20492 1.28219 1.35213 1.41151 1.47106 1.52144 1.56664 1.58475

0.90802 0.95453 0.98131 1.05077 1.10059 1.20001 1.27702 1.34682 1.40607 1.46549 1.51581 1.56092 1.57893

0.90369 0.95013 0.97684 1.04613 1.09568 1.19490 1.27177 1.34137 1.40046 1.45982 1.51002 1.55497 1.57301



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Table 3. continued 10−3·d/(kg·m−3) T/K x1 0.0178 0.0671 0.1007 0.1937 0.3006 0.3995 0.5041 0.5544 0.6039 0.6990 0.8104 0.8588 0.9093 0.9408 a

293.15 0.98458 1.08539 1.14143 1.26204 1.35987 1.42694 1.48189 1.50395 1.52358 1.55620 1.58798 1.60009 1.61190 1.61879

298.15 0.97997 1.08045 1.13639 1.25672 1.35442 1.42153 1.47658 1.49881 1.51830 1.55076 1.58220 1.59419 1.60585 1.61270

303.15

308.15

[BMIM][FAP] (1) + DMA (2) 0.97521 0.97038 1.07546 1.07043 1.13127 1.12610 1.25139 1.24603 1.34896 1.34348 1.41597 1.41040 1.47087 1.46514 1.49301 1.48720 1.51255 1.50669 1.54523 1.53919 1.57669 1.57070 1.58860 1.58265 1.60018 1.59429 1.60701 1.60119

313.15

318.15

323.15

0.96549 1.06532 1.12090 1.24061 1.33793 1.40455 1.45933 1.48129 1.50082 1.53327 1.56479 1.57679 1.58845 1.59531

0.96049 1.06015 1.11562 1.23512 1.33208 1.39883 1.45359 1.47558 1.49506 1.52742 1.55889 1.57089 1.58250 1.58939

0.95545 1.05492 1.11029 1.22957 1.32656 1.39316 1.44773 1.46976 1.48913 1.52148 1.55285 1.56480 1.57650 1.58341

The combined experimental uncertainties (k = 2) are u(d) = 2·10−2 kg·m−3, u(x) = 5·10−5, and u(T) = 0.01 K.

Comparing the results obtained for the binary mixtures of pyrrolidinium-based ionic liquid [BMPYR][FAP] and identical amide,26 lower values of VE for the investigated systems with [BMIM][FAP] can be observed. This behavior can be explained by the smaller steric hindrance of [BMIM]+ and the possibility of [BMIM]+ to interact through a partially negatively charged oxygen atom of the carbonyl group as well as the capability of forming a weak hydrogen bond between the proton at the C2 atom of the imidazole ring as a proton donor and a carbonyl oxygen atom of the amide.51−53 Knowing the Redlich−Kister’s coefficients Ai and the molar volumes of the pure components, Vo1 ([BMIM][FAP]) and Vo2 (amides), the partial molar volumes of the components, V1 and V2, can be derived from the expressions 3 and 4: i=n

V1o

2

+ (1 − x1)

∑ Ai(1 − 2x1)i − 2x1(1 − x1)2

Figure 1. Excess molar volumes for ([BMIM][FAP] + amides) binary mixtures as a function of the [BMIM][FAP] mole fraction at the temperature T = 298.15 K: ■, NMF; ●, DMF; △, NEF; ▽, DBF; ◀, DMA. The lines represent the Redlich−Kister type fittings with the parameters indicated in the Table S2.

V1 =

values of VE comparing with those systems with protic amides (NMF, NEF) due to a steric hindrance of the amide carbonyl group and weakening the ion−dipole interactions between [BMIM]+ ion and partially negatively charged oxygen atom of the amide carbonyl group. Also, additional methyl groups substituted on the nitrogen atom of both protic and aprotic amide shift the maximum of VE toward higher mole fraction of ionic liquid. Comparing the values of VE obtained for DMF and DMA, it can be seen that the methyl group on the carbon atom does not lead to the shift of VE maximum position. Variations of VE with temperature for all investigated systems are presented in Table S1 and in the Figures S1−S5 in the Supporting Information. It can be seen from these figures that increase of temperature has no significant influence on the variation of VE in the case of DMF and DMA. A slight decrease of VE is noted for the mixtures with DBF. The increase of temperature in the mixtures with protic amides (NMF and NEF) causes geometric disorder and prominent increase of the VE at higher temperatures.

V2 = V 2o + x12 ∑ Ai (1 − 2x1)i + 2x12(1 − x1) ·

i=0 i=n

· ∑ Ai (i)(1 − 2x1)i − 1 i=0

(3)

i=n i=0 i=n

∑ Ai(i)(1 − 2x1)i− 1 i=0

(4)

The values for the partial molar volumes are given in Table S1 in the Supporting Information and in Figure 2. In the mixtures of [BMIM][FAP] and amides with longer alkyl chains (NEF and DBF), the values of the partial and apparent molar volumes of [BMIM][FAP] increase at low [BMIM][FAP] mole fractions, reaching a maximum at x1 = 0.2. For mixtures with shorter alkyl substituents at the N atom of the amide (NMF, DMF, and DMA), both partial and apparent molar volumes of the ionic liquid decrease with an increase of the ionic liquid mole fraction. Such a difference is due to the possibility of hydrophobic interactions between the alkyl substituents on the amide N atom with the butyl group of the imidazolium ion and the entire hydrophobic [FAP] anion. 3375



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Vϕ2 =

(d1 − d) M + 2 m2dd1 d

(10)

The m1 and m2 are molalities related to [BMIM][FAP] and amides, respectively. The apparent molar volumes are reported in Table S1 in the Supporting Information and in Figure 3.

Figure 2. Partial molar volumes of ([BMIM][FAP] + amides) binary mixtures as a function of [BMIM][FAP] mole fraction at T = 298.15 K; ■, NMF; ●, DMF; △, NEF; ▽, DBF; ◀, DMA.

These conclusion are in accordance with the results obtained from the literature.54,55 If x1 = 0 or x2 = 0, eqs 3 and 4 may be transformed into:

Figure 3. Apparent molar volumes of ([BMIM][FAP] + amides) binary mixtures as a function of [BMIM][FAP] mole fraction at T = 298.15 K; ■, NMF; ●, DMF; △, NEF; ▽, DBF; ◀, DMA.

i=n

V1∞ = V1o +

∑ Ai(−1)i (x1 → 0) i=0

(5)

i=n

V 2∞ = V 2o +

∑ Ai(x2 → 0) i=0

V∞ 1

Knowing the values of the apparent molar volume Vϕ1 and molar volume of the ionic liquid Vo1, the excess apparent molar volume VEϕ1 can be calculated according to following relation:

(6)

V∞ 2

where and are the partial molar volumes of the components at infinite dilution. At this stage ion−ion interactions can be neglected. Thus, calculated partial molar volumes at infinite dilution will provide useful information about ion−dipole interactions. Partial excess molar volumes at infinite dilution of the components, (VE1 )∞ and (VE2 )∞, can be calculated after the rearrangement of the eqs 5 and 6:

VϕE1 = Vϕ1 − V1o

The excess apparent molar volumes are calculated for the mixtures of [BMIM][FAP] with investigated amides and also for [BMPYRR][FAP] mixtures with the same amides and reported in Table S4 in the Supporting Information. Values of the apparent molar volumes and molar volume of [BMPYRR][FAP] necessary for the calculation were taken from our previous work.26 Comparing the values of VEϕ1 calculated for these systems, it can be noted that the lower values were obtained in the mixtures of [BMIM][FAP] in the whole composition and temperature range. This is in accordance with the assumption and conclusion that binary mixtures with the [BMIM]+ cation forms stronger interactions with amides compared to [BMPYRR]+ based ionic liquids.56 On the basis of the volumetric data, the isobaric thermal expansivity can be calculated. At constant molality, the corresponding isobaric thermal expansion coefficients can be calculated using the relation 12:

i=n

(V1E)∞ =

∑ Ai(−1)i i=0

(7)

i=n

(V2E)∞ =

∑ Ai i=0

(8)

The partial molar volumes at infinite dilution and partial excess molar volumes at infinite dilution are listed in Table S3 in the Supporting Information. Positive values of partial excess molar volumes at infinite dilution were observed in all studied systems, indicating weaker ion−dipole interaction between the amides and the ionic liquid compared with the interactions in the pure ionic liquid and amides. Slightly higher values for DMA, DMF, and DBF compared to NMF and NEF are the result of higher relative permittivity of NMF and NEF (εNMF = 182.4; εDMF = 36.7; εDMA = 37.8; εNEF = 102.7; εDBF = 18.0). The apparent molar volumes, Vϕ1 for [BMIM][FAP] and Vϕ2 for selected amides, were calculated using the experimental density values: Vϕ1 =

(d 2 − d ) M + 1 m1dd 2 d

(11)

αp = −

1 ⎛ ∂d ⎞ ⎜ ⎟ d ⎝ ∂T ⎠ P

(12)

Calculated values of αp are given in Table S5 in the Supporting Information at different temperatures. Also, the excess thermal expansions, αEp , were calculated at T = 293.15 K using eq 13: i=2

αpE = αp −

∑ ϕα i ip i=1

(13)

where ϕ is the volume fraction of component i, defined as

(9) 3376



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i=2

ϕi = xiV io/∑ xiV io i=1

of the binary mixtures as a function of [bmim][NTf2] at different temperatures. This material is available free of charge via the Internet at http://pubs.acs.org.

(14)

■

The obtained results are presented in Figure 4. As it can be seen from Figure 4, the binary mixtures of ionic liquid with

AUTHOR INFORMATION

Corresponding Author

*Tel.: +381 21 485 2744; fax: +381 21 454 065; e-mail: [email protected]. Funding

This work was financially supported by the Ministry of Education and Science of Serbia under project contract ON172012 and The Provincial Secretariat for Science and Technological Development of APV. Notes

The authors declare no competing financial interest.

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Figure 4. Variation of excess thermal expansion coefficients of ([BMIM][FAP] + amides) binary mixtures as a function of [BMIM][FAP] volume fraction, Φ1, at T = 298.15 K; ■, NMF; ●, DMF; △, NEF; ▽, DBF; ◀, DMA.

NMF and NEF have positive values of excess thermal expansion coefficient, which is typical for the systems containing molecules capable to self-associate.57 These two protic amides realize self-association through NH···CO hydrogen bonding.24

4. CONCLUSION Volumetric properties of binary liquid mixtures [BMIM][FAP] ionic liquid with five different amides are presented in this paper at various temperatures and at atmospheric pressure in the whole composition range. Based on the experimental density values, the excess molar volumes, apparent and partial molar volumes, and excess molar volumes at infinite dilution were calculated. Mixtures containing aprotic amides (DMF, DBF, DMA) have higher values of VE compared to systems with protic amides (NMF, NEF) due to the steric hindrance of the amide carbonyl group. Also, the coefficient of thermal expansion and the excess of thermal expansion coefficient were calculated. It was shown that mixtures containing molecules like NMF and NEF which are capable to self-associate through hydrogen bonding have positive values of excess thermal expansion coefficient.

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REFERENCES

ASSOCIATED CONTENT

S Supporting Information *

Density, excess molar volume, apparent molar volume, and partial molar volume of the studied mixtures (Table S1); Redlich−Kister fitting coefficients of the VE of the binary mixtures as a function of temperatures (Table S2); partial molar volume and partial molar excess volume at infinite dilution for the components of the mixtures studied at different temperatures (Table S3); excess apparent molar volume of [BMIM][FAP] and [BMPYRR][FAP] with amides (Table S4); thermal expansion coefficients as a function of temperatures for the investigated mixtures; and figures of the excess molar volumes 3377



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Volumetric Properties of Binary Mixtures of 1-Butyl-3

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