Thermophysical Properties of Dicationic Ionic Liquids under the

Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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Thermophysical Properties of Dicationic Ionic Liquids under the Influence of Amino Acid Dinesh V. Kawadkar and Sangesh P. Zodape* Department of Chemistry, Visvesvaraya National Institute of Technology, Nagpur, 440 010, India

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S Supporting Information *

ABSTRACT: Thermodynamic properties are supportive in describing the structure and properties of solutions concerning solute−solute and solute−solvent interactions. With this regard experimental values of densities (ρ), speeds of sound (u), and absolute viscosities (η) of butyl and pentyl dicationic ionic liquids (DILs) as binary [C(n)−DIL + water] and ternary [C(n)−DIL+ glycine + water] systems where (n = 4, 5) have been studied at different temperatures at T = (293.15−313.15 K). The densities of DILs decrease with the increase in alkyl chain length having imidazolium cations with the rise in temperature. It may be due to the bulkiness of the longer alkyl chains preventing them from efficient close packing leading to a decrease in the density. The molecular interactions are discussed in terms of apparent molar volume (Vϕ), apparent molar isentropic compressibility (κϕ), Jones−Dole coefficient of viscosity supported with the partial molar volume of transfer (ΔtrVϕ0), partial molar compressibility of transfer (Δtrκ0ϕ) and transfer values of B coefficient of DILs from water to 0.06 mol·kg−1 aqueous systems of glycine. These structural interactions for studied DILs−glycine pairs in water have been also discussed and interpreted by thermal study and electrochemical study.

1. INTRODUCTION ILs are omnipresent in recent chemical literature. The synthesis and applications of ILs has exponentially grown over the past decades in the areas of science, academia, and industry. For ILs, the small structural variation in cations and anions results in a noticeable change in their distinctive physicochemical properties. These are solvents which entirely comprise ions only.1 The selected cations of ILs are organic, whereas anions may be either an organic or inorganic moiety. The ILs by the virtue of their uniqueness are used as “designer solvents”, and biochemical processes, extraction processes, catalysis, electrochemical, analytical, and carbohydrate chemistry, bimolecular dissolution, solar cells, and fuel technology are prominently improved.2−8 Because of their potential application, ILs can be used in food industries for the extraction of various dyes from chilli powder, which can then be analyzd by high performance liquid chromatography (HPLC).9−11 The investigation of flavors from various botanical multiplicities of cinnamon produced an “electric nose” which is coated by quartz crystals, reported by Toniolo et al.12 They got favorable results for CO2/N2 and CO2/CH4 separation due to supported ionic liquid membranes (SILMs) separating the N2 and CH4 gases. Fang et al. discussed biodiesel synthesis from various long chain free fatty acids or with low molecular weight alcohols by using halogen-free dicationic ILs (DILs).13 The area of geminal dicationic or oligocationic ILs is rather understudied. These ILs are promising and improved to a larger magnitude than © XXXX American Chemical Society

monocationic ILs (the cations component may be identical and can be separately functionalized).14 The vital and strategic improvement of substitute energy sources to diminishing fossil fuel is a crucial obligation for society. Few distinctive properties have been detected in ionic liquids compared to salts or standard buffers which regulate that they can be used as additives in aqueous solutions in many bioprocesses.15 Among accessible alternatives, biomass conversion to biofuel and other value-added products requires accurate determination of thermodynamic properties, improvement of models, design development, and optimization. ILs are a universal material present in the research of biomass functionalization and conversion. Saccharides are extracted from the biomass, and they can be further converted into aldehydes such as furfural. Also, they the ILs are used to improve and soften the polysaccharides (lignin, cellulose, and hemicellulose) of biomass.16−20 Furthermore; the occurrence of a small amount of water can intensely disturb the physical and chemical properties of the ionic liquid phase. To realize the strength of interactions prevailing between amino acids and basic DILs, herein we report experimental densities, speeds of sound, and absolute viscosities (for fluid flow and diffusion of gases) of two DILs namely 1,4-bis (3methylimidazolium-1-yl) butane dibromide or (1,1-(butaneReceived: May 1, 2018 Accepted: December 4, 2018

A

DOI: 10.1021/acs.jced.8b00349 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

Table 1. Provenance, CAS Registry Number and Mass Fraction Purity of the Chemicals chemical name

provenance

CASRN

1-methylimidazole 1,4-dibromobutane 1,5-dibromopentane glycine C4-DIL C5−DIL

Sigma-Aldrich Alfa Aesar Alfa Aesar Merck synthesis synthesis

616-47-7 110-52-1 111-24-0 56-40-6

purification method ̵ ̵

vacuumcdrying vacuumc drying

mass fraction purity ≥0.99a ≥0.98a ≥0.98a ≥0.98a ≥0.98b ≥0.98b

analysis method ̵ ̵

NMR, K.F. analysis NMR, K.F. analysis

a Purity of chemicals was provided by suppliers and used without further purification. bThe purity of synthesized DILs was estimated by 1H NMR spectra, and water content was estimated by Karl Fischer titrator. cAll synthesized DILs were used after drying in a vacuum oven for 24 h.

butane dibromide or 1,1- (butane-1,4-diyl)-bis (3-methyl-1Himidazolium-1-yl) dibromide and 1,5-bis (3-methylimidazolium-1-yl) pentane dibromide or 1,1-(pentane-1,5-diyl)-bis (3methyl-1H-imidazolium-1-yl) dibromide.20−22 [C4-DIL]: 1H NMR (400 MHz, DMSO-d6), spectrum contains peaks at: δ 9.34 (s, 1Η), 9.28 (s, 1Η), 7.86−7.84 (d, J = 8.4 Hz, 2H), 7.76−7.75 (d, J = 6.8 Hz, 2H), 4.26−4.22 (t, J = 6.4 Hz, 4H), 3.87 (s, 6H), 1.81−1.74 (m, 4H). 13C NMR (100 MHz, DMSO-d6): δ 136.11, 123.20, 121.85, 47.84, 34.34, 28.03. [C5-DIL]: 1H NMR (400 MHz, DMSO-d6): δ 9.28 (s, 2Η), 7.84−7.81(d, J = 12.4 Hz, 2Η), 7.76−7.74 (d, J = 6.8 Hz, 2Η), 4.21−4.17 (t, J = 6.8 Hz, 4H), 3.86 (s, 6H), 1.87−1.77 (m, 4H), 1.28−1.17 (m, 2H). 13C NMR (100 MHz, DMSO-d6): δ 136.69, 123.57, 45.57, 35.88, 29.55. 2.3. Measurements and Methods. Before measuring the physicochemical properties, to reduce the water content both DILs were dried under low pressure by placing them in a vacuum for 72 h at moderate temperature of 353.15 K. The glycine sample was similarly dried in a vacuum oven for at least 48 h before use. Solutions were prepared by using Millipore quality freshly degassed water (specific conductance 0.5 μS· cm−1) on the molar mass basis over the concentration range (0.01 to 0.15) mol·kg−1 at room temperature. It was prepared by weighing with the electronic balance (Shimadzu AUW220D) with an accuracy of ±0.01 mg. The water content in the ionic liquids was accounted in terms of molality corrections for solution preparations. An automated digital density and sound velocity meter (DSA 5000 M, Anton Paar, Austria) was used to measure the densities and speeds of sound for synthesized DILs in different medium at the studied temperature from T = (293.15 to 313.15) K at 0.1 MPa pressure. The instrument follows an oscillating U-tube principle and sound velocity cell also connected at one end of the U-tube. The measurements can be done by inserting the bubble-free sample without changing the sample conditions in the cycle at different studied temperatures. The working frequency of the inbuilt speed analyzer is 3 MHz. By using a microviscometer (Lovis 2000 ME) viscosity module the absolute viscosities were measured. The instrument follows the rolling ball principle. The temperature of density and speed of sound measurements were controlled by a built-in precise Peltier thermostat with an accuracy ±0.03 K. The density and sound velocity meter was calibrated by performing the air/ water check adjustment with ultrapure water and dry air with atmospheric pressure. The reliability of the instrument was checked by measuring the densities of aqueous NaCl solutions at different temperatures. The uncertainty in experimental measurements of the density was found to ±0.05 kg·m−3, so the combined expanded uncertainty was calculated to be Uρ(ρ) = 0.1 kg·m−3. The uncertainty in the speed of sound measurement was found to be ±0.5 m·s−1, and the combined

1,4-diyl)-bis (3-methyl-1H-imidazolium-1-yl) dibromide) or C4-DIL and 1,5-bis (3-methylimidazolium-1-yl) pentane dibromide or (1,1-(pentane-1,5-diyl)-bis (3-methyl-1H-imidazolium-1-yl) dibromide) or C5-DIL that is, [C(n)-DIL] where n = 4, 5 in 0.06 mol·kg−1 aqueous glycine solution at different temperatures T = (293.15 to 313.15) K. With the help of basic experimental data, apparent molar volume (Vϕ), apparent molar isentropic compression (κϕ) of the solute and Jones− Dole viscosity coefficients were calculated. Limiting values of solute are obtained by applying the Debye−Hückel equation and from a smooth extrapolation curve to zero concentration. Also, the partial molar volume of transfer (ΔtrV0ϕ) and partial molar compressibility of transfer (Δtrκ0ϕ) were obtained for studied systems.

2. EXPERIMENTAL SECTION 2.1. Materials. All starting materials were used as received without further purification treatment. These materials included 1-methylimidazole (Sigma-Aldrich, ≥0.99), 1,4dibromobutane (Alfa Aesar, ≥0.98), 1,5-dibromopentane (Alfa Aesar, ≥0.98), glycine (Merck, ≥0.98), methanol (Merck, ≥0.98), ethyl acetate (Merck, ≥0.98). All chemicals were available from the commercial supplier and used without further purification. The details of the chemicals and synthesized DILs are mentioned in Table 1. 2.2. Synthesis and Characterization of DILs. The purity of synthesized geminal dicationic ionic liquids was confirmed by characterization with 1H and 13C NMR spectra recorded on a Bruker Avance II 400 spectrometer in DMSO. Both synthesized DILs have a mass fraction purity ≥ 0.98. The water content in the DILs (0.32, and 0.38%) was measured using a Karl Fisher coulometer titrator (DL 32, Mettler Toledo) with an uncertainty of 0.05 μg. Thermal decomposition temperature was conducted by the thermal analyzer (TG-DTA 7200 Hitachi, Japan) at a single heating rate of 10 °C·min−1 with the precision of ±0.01 μg weighing under a nitrogen atmosphere. Electrochemical measurements were carried out with a computer−controlled Parstat 4000 potentiostat (Princeton Applied Research Ametek) using a three electrode system. A platinum spiral wire was used as the counter electrode, CPE, Ag/AgCl electrodes were used as working and reference electrodes, respectively, in a conventional and two-compartment electrochemical cell. 2.2.1. Synthesis of C4-DIL and C5-DIL. 1,4-dibromobutane (4.31 g, 20 mmol) or 1,5-dibromopentane (4.6 g, 20 mmol) is stirred in methanol with 1-methylimidazole and refluxed for 24 h. Then the precipitate obtained was washed several times using ethyl acetate (25 mL) by decantation. It was stirred in ethyl acetate (100 mL) to dissolve within 30 min. Finally, the ethyl acetate was removed by slow evaporation under vacuum to obtain the desired 1,4-bis (3-methylimidazolium-1-yl) B



Article

Table 2. Molality (m), Density (ρ), Speed of Sound (u), Absolute Viscosity (η), Apparent Molar Volume (Vϕ), Isentropic Compressibility (κs), Apparent Molar Isentropic Compressibility (κϕ) and Relative Viscosity of Binary (DIL + Water) and Ternary (DIL + Water + Glycine) Systems at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K and p = 0.1 MPaa,b

m mol ·kg −1c

10−3ρ kg·m−3

u m·s−1

η mPa·s

0.000000 0.049440 0.067106 0.079117 0.092701 0.102136

0.998203 1.004657 1.006895 1.008403 1.010062 1.011220

1482.34 1489.79 1492.04 1493.51 1495.09 1496.15

1.005 1.026 1.034 1.039 1.044 1.049

0.000000 0.049440 0.067106 0.079117 0.092701 0.102136

0.997043 1.003451 1.005676 1.007176 1.008823 1.009971

1496.69 1503.20 1505.18 1506.56 1508.02 1509.04

0.894 0.914 0.921 0.926 0.931 0.935

0.000000 0.049440 0.067106 0.079117 0.092701 0.102136

0.995645 1.002008 1.004216 1.005705 1.007350 1.008490

1509.13 1515.43 1517.11 1518.48 1519.82 1520.74

0.801 0.821 0.828 0.833 0.839 0.842

0.000000 0.049440 0.067106 0.079117 0.092701 0.102136

0.994029 1.000353 1.002541 1.004031 1.005667 1.006798

1519.81 1524.65 1526.34 1527.34 1528.88 1529.51

0.723 0.744 0.751 0.756 0.762 0.765

0.000000 0.049440 0.067106 0.079117 0.092701 0.102136

0.992212 0.998497 1.000679 1.002150 1.003787 1.004913

1529.18 1534.14 1535.46 1536.52 1537.79 1538.53

0.656 0.677 0.683 0.688 0.692 0.696

0.000000 0.033408 0.046145 0.056461 0.067169 0.077700 0.088571 0.096710

0.998203 1.002346 1.003887 1.005111 1.006381 1.007584 1.008848 1.009748

1482.34 1488.33 1490.29 1491.61 1493.35 1494.77 1496.36 1497.33

1.005 1.021 1.027 1.032 1.037 1.042 1.047 1.050

0.000000 0.033408 0.046145 0.056461 0.067169 0.077700 0.088571 0.096710

0.997043 1.001165 1.002702 1.003913 1.005173 1.006381 1.007621 1.008512

1496.69 1501.92 1503.69 1505.02 1506.46 1507.80 1509.22 1510.21

0.894 0.908 0.914 0.918 0.924 0.928 0.933 0.936

106 ·Vϕ

1015·(κs)

1015·(κϕ)

m 3·mol−1

m 2·N−1

m 5·N−1·mol−1

ηr

45.59 44.85 44.61 44.46 44.29 44.18

−69.9 −42.2(±4.6) −37.5(±3.9) −34.9(±3.6) −31.9(±3.3) −30.1(±3.1)

1.000 1.021 1.029 1.034 1.039 1.044

44.77 44.10 43.89 43.74 43.59 43.48

−56.5 −32.4(±4.5) −27.4(±3.8) −25.4(±3.5) −22.8(±3.2) −21.5(±3.1)

1.000 1.022 1.030 1.036 1.041 1.046

44.10 43.45 43.25 43.12 42.98 42.88

−42.8 −23.7(±4.4) −19.2(±3.7) −16.7(±3.4) −14.6(±3.2) −13.4(±3.0)

1.000 1.025 1.034 1.040 1.047 1.051

43.55 43.00 42.81 42.69 42.55 42.46

−30.7 −15.5(±4.3) −11.7(±3.7) −9.6 (±3.4) −7.9 (±3.1) −6.1 (±3.0)

1.000 1.029 1.039 1.046 1.054 1.058

43.10 42.55 42.38 42.27 42.14 42.05

−17.3 −6.3(±4.2) −2.6 (±3.6) 0.5 (±3.3) 1.5 (±3.1) 2.2 (±2.9)

1.000 1.032 1.041 1.049 1.055 1.061

45.59 45.04 44.85 44.72 44.56 44.42 44.27 44.17

−73.4 −48.1(±5.6) −42.6(±4.8) −36.8(±4.3) −32.8(±3.9) −36.0(±3.6) −31.3(±3.4) −28.7(±3.2)

1.000 1.016 1.022 1.027 1.032 1.037 1.042 1.045

44.77 44.28 44.11 44.98 43.84 43.71 43.57 43.48

−61.9 −37.7(±5.5) −32.2(±4.6) −28.1(±4.2) −25.7(±3.8) −23.2(±3.5) −21.5(±3.3) −19.7(±3.1)

1.000 1.016 1.022 1.027 1.034 1.038 1.044 1.047

C4-DIL + Water T = 293.15 K 244.49 246.08(±1.01) 246.54(±0.75) 246.77(±0.63) 247.35(±0.54) 247.55(±0.49) T = 298.15 K 245.48 247.15(±1.01) 247.57(±0.75) 247.77(±0.63) 248.36(±0.54) 248.57(±0.49) T = 303.15 K 246.72 248.24(±1.01) 248.67(±0.75) 248.87(±0.63) 249.35(±0.54) 249.57(±0.49) T = 308.15 K 247.80 249.23(±1.01) 249.76(±0.75) 249.81(±0.63) 250.28(±0.54) 250.53(±0.49) T = 313.15 K 248.88 250.25(±1.01) 250.67(±0.75) 250.86(±0.63) 251.20(±0.54) 251.43(±0.49) C5-DIL + Water T = 293.15 K 265.49 267.14(±1.50) 267.56(±1.08) 268.06(±0.89) 268.32(±0.74) 269.01(±0.64) 269.22(±0.56) 269.78(±0.52) T = 298.15 K 266.14 267.94(±1.50) 268.28(±1.08) 268.91(±0.89) 269.21(±0.74) 269.74(±0.64) 270.16(±0.56) 270.75(±0.52) C



Article

Table 2. continued

m mol ·kg −1c

10−3ρ kg·m−3

u m·s−1

0.000000 0.033408 0.046145 0.056461 0.067169 0.077700 0.088571 0.096710

0.995645 0.999742 1.001267 1.002472 1.003729 1.004930 1.006162 1.007048

1509.13 1514.37 1515.88 1517.12 1518.45 1519.77 1520.88 1521.85

0.000000 0.033408 0.046145 0.056461 0.067169 0.077700 0.088571 0.096710

0.994029 0.998108 0.999627 1.000825 1.002073 1.003267 1.004502 1.005384

1519.81 1523.67 1525.12 1526.36 1527.42 1528.66 1529.86 1530.71

0.000000 0.033408 0.046145 0.056461 0.067169 0.077700 0.088571 0.096710

0.992212 0.996275 0.997783 0.998981 1.000221 1.001410 1.002642 1.003533

1529.18 1533.24 1534.34 1535.36 1536.48 1537.54 1538.64 1539.43

0.000000 0.019697 0.031683 0.042218 0.053029 0.063585 0.073770 0.085802 0.095933

1.000193 1.002737 1.004261 1.005585 1.006931 1.008228 1.009470 1.010917 1.012123

1485.80 1489.55 1491.67 1492.24 1494.78 1495.32 1496.81 1497.09 1498.26

0.000000 0.019697 0.031683 0.042218 0.053029 0.063585 0.073770 0.085802 0.095933

0.999024 1.001559 1.003078 1.004396 1.005736 1.007028 1.008264 1.009712 1.010915

1499.60 1503.10 1504.85 1505.21 1507.63 1508.88 1509.05 1510.36 1510.31

0.000000 0.019697 0.031683 0.042218 0.053029 0.063585 0.073770 0.085802

0.997613 1.000141 1.001657 1.002969 1.004311 1.005598 1.006830 1.008268

1511.82 1513.84 1515.38 1516.67 1517.79 1518.86 1519.92 1520.99

η mPa·s

106 ·Vϕ 3

−1

m ·mol

T = 303.15 K 267.16 268.90(±1.50) 269.29(±1.08) 269.89(±0.89) 270.11(±0.74) 270.64(±0.64) 271.07(±0.56) 271.66(±0.52) T = 308.15 K 0.723 267.96 0.737 269.68(±1.50) 0.741 270.06(±1.08) 0.747 270.69(±0.89) 0.752 270.96(±0.74) 0.757 271.51(±0.64) 0.762 271.82(±0.56) 0.766 272.42(±0.52) T = 313.15 K 0.656 268.82 0.670 270.44(±1.50) 0.676 270.92(±1.08) 0.681 271.45(±0.89) 0.685 271.77(±0.74) 0.689 272.31(±0.64) 0.694 272.60(±0.56) 0.697 273.06(±0.52) C4-DIL + Water + Glycine T = 293.15 K 1.012 247.36 1.021 248.19(±2.54) 1.026 248.57(±1.58) 1.032 248.92(±1.18) 1.037 249.23(±0.94) 1.042 249.60(±0.79) 1.047 249.90(±0.68) 1.053 250.31(±0.58) 1.058 250.63(±0.52) T = 298.15 K 0.908 247.98 0.916 248.79(±2.54) 0.921 249.15(±1.58) 0.925 249.53(±1.18) 0.929 249.87(±0.94) 0.934 250.24(±0.79) 0.938 250.55(±0.68) 0.943 250.88(±0.58) 0.947 251.19(±0.52) T = 303.15 K 0.811 248.42 0.819 249.31(±2.54) 0.824 249.64(±1.58) 0.827 250.09(±1.18) 0.832 250.31(±0.94) 0.836 250.72(±0.79) 0.840 251.04(±0.68) 0.845 251.44(±0.58) 0.801 0.815 0.821 0.825 0.830 0.835 0.839 0.843

D

1015·(κs)

1015·(κϕ) m ·N−1·mol−1

ηr

44.10 43.62 43.46 43.34 43.21 43.08 43.97 42.88

−50.2 −28.2(±5.4) −21.6(±4.5) −18.2(±4.0) −16.4(±3.7) −14.8(±3.5) −11.9(±3.2) −10.7(±3.1)

1.000 1.017 1.025 1.030 1.036 1.042 1.047 1.052

43.55 43.16 43.01 42.89 42.77 42.65 42.53 42.45

−35.1 −17.3(±5.3) −12.3(±4.5) −10.9(±4.0) −7.8(±3.7) −6.6(±3.4) −5.4(±3.0) 3.9(±3.0)

1.000 1.019 1.025 1.033 1.040 1.047 1.054 1.059

43.10 42.70 42.57 42.46 42.35 42.24 42.13 42.05

−18.2 −6.0(±5.2) −0.1(±4.4) 1.8(±4.0) 2.5(±3.6) 3.6(±3.4) 4.3(±3.1) 5.2(±3.0)

1.000 1.021 1.030 1.038 1.044 1.050 1.058 1.063

45.29 44.95 44.75 44.60 44.45 44.30 44.16 44.02 43.90

−93.7 −67.5(±7.3) −61.8(±5.7) −55.1(±4.9) −50.0(±4.4) −46.9(±4.0) −44.7(±3.7) −39.2(±3.4) −36.2(±3.2)

1.000 1.009 1.014 1.020 1.025 1.030 1.035 1.041 1.045

44.51 44.19 44.02 43.89 43.74 43.62 43.50 43.36 43.25

−66.5 −46.4(±7.1) −41.0(±5.6) −36.1(±4.8) −33.2(±4.3) −30.0(±3.9) −27.3(±3.6) −24.5(±3.3) −21.6(±3.1)

1.000 1.009 1.014 1.019 1.023 1.029 1.033 1.039 1.043

43.86 43.63 43.48 43.36 43.23 43.11 42.99 42.87

−43.9 −28.4(±7.0) −23.8(±5.5) −20.2(±4.7) −18.5(±4.2) −15.8(±3.8) −15.3(±3.5) −12.3(±3.3)

1.000 1.010 1.016 1.020 1.026 1.031 1.036 1.042

2

m ·N

−1

5



Article

Table 2. continued

m mol ·kg −1c

10−3ρ kg·m−3

u m·s−1

0.095933

1.009460

1521.89

0.000000 0.019697 0.031683 0.042218 0.053029 0.063585 0.073770 0.085802 0.095933

0.995985 0.998508 1.000016 1.001332 1.002667 1.003946 1.005185 1.006621 1.007807

1522.38 1525.21 1526.38 1527.37 1528.32 1529.32 1530.15 1531.26 1532.22

0.000000 0.019697 0.031683 0.042218 0.053029 0.063585 0.073770 0.085802 0.095933

0.994125 0.996641 0.998144 0.999456 1.000785 1.002066 1.003305 1.004735 1.005925

1531.37 1533.22 1534.32 1534.01 1535.75 1536.45 1537.05 1538.01 1538.43

0.000000 0.027913 0.040000 0.052690 0.065060 0.075000 0.089265 0.101740

1.000193 1.003646 1.005092 1.006584 1.008018 1.009150 1.010762 1.012106

1485.80 1491.44 1493.24 1494.89 1496.64 1498.04 1499.58 1501.18

0.000000 0.027913 0.040000 0.052690 0.065060 0.075000 0.089265 0.101740

0.999024 1.002449 1.003890 1.005372 1.006804 1.007923 1.009511 1.010835

1499.60 1505.22 1506.83 1508.29 1509.98 1511.05 1512.52 1513.83

0.000000 0.027913 0.040000 0.052690 0.065060 0.075000 0.089265 0.101740

0.997613 1.001022 1.002452 1.003925 1.005339 1.006443 1.008019 1.009337

1511.82 1515.06 1517.46 1519.00 1520.29 1521.39 1522.71 1524.00

0.000000 0.027913 0.040000 0.052690 0.065060 0.075000

0.995985 0.999378 1.000806 1.002266 1.003683 1.004771

1522.38 1527.26 1528.61 1529.86 1531.27 1532.11

η mPa·s

106 ·Vϕ 3

−1

m ·mol

T = 303.15 K 251.83(±0.52) T = 308.15 K 0.733 248.94 0.741 249.77(±2.54) 0.746 250.26(±1.58) 0.750 250.50(±1.18) 0.754 250.82(±0.94) 0.758 251.30(±0.79) 0.762 251.48(±0.68) 0.767 251.87(±0.58) 0.771 252.30(±0.52) T = 313.15 K 0.666 249.60 0.673 250.35(±2.54) 0.678 250.87(±1.58) 0.682 251.12(±1.18) 0.687 251.47(±0.94) 0.691 251.85(±0.79) 0.695 251.99(±0.68) 0.700 252.42(±0.58) 0.704 252.77(±0.52) C5-DIL+ Water + Glycine T = 293.15 K 1.012 265.69 1.026 267.34(±1.79) 1.033 268.18(±1.25) 1.039 268.96(±0.95) 1.045 269.59(±0.77) 1.051 270.12(±0.67) 1.058 270.71(±0.56) 1.064 271.64(±0.49) T = 298.15 K 0.908 266.68 0.920 268.52(±1.79) 0.925 269.18(±1.25) 0.931 269.95(±0.95) 0.935 270.46(±0.77) 0.939 271.08(±0.67) 0.946 271.82(±0.56) 0.951 272.84(±0.49) T = 303.15 K 0.811 267.38 0.822 269.30(±1.79) 0.828 270.07(±1.25) 0.833 270.86(±0.95) 0.838 271.51(±0.77) 0.842 272.23(±0.67) 0.848 272.96(±0.56) 0.853 273.93(±0.49) T = 308.15 K 0.733 268.10 0.745 270.12(±1.79) 0.749 270.77(±1.25) 0.755 271.70(±0.95) 0.760 272.20(±0.77) 0.764 273.08(±0.67) 0.849

E

1015·(κs)

1015·(κϕ) m ·N−1·mol−1

ηr

42.77

−10.3(±3.1)

1.047

43.32 43.06 42.93 42.82 42.70 42.59 42.49 42.37 42.26

−31.2 −13.0(±6.8) −11.0(±5.4) −6.9 (±4.6) −5.7 (±4.1) −5.3 (±3.8) −3.4 (±3.5) −2.4 (±3.2) −1.7(±3.0)

1.000 1.011 1.018 1.023 1.029 1.034 1.040 1.046 1.052

42.89 42.69 42.58 42.47 42.37 42.27 42.18 42.07 41.99

−18.1 1.0 (±6.8) 3.7 (±5.3) 4.3 (±4.6) 5.3 (±4.1) 6.4 (±3.7) 8.4 (±3.4) 8.6 (±3.1) 10.9(±3.0)

1.000 1.011 1.018 1.024 1.032 1.038 1.044 1.051 1.057

45.29 44.79 44.62 44.46 44.29 44.16 44.00 43.84

−99.6 −61.9(±6.1) −50.2(±5.1) −40.6(±4.4) −35.9(±3.9) −33.1(±3.7) −27.0(±3.3) −24.0(±3.1)

1.000 1.014 1.021 1.027 1.033 1.039 1.045 1.051

44.51 44.03 43.87 43.72 43.56 43.45 43.30 43.17

−87.8 −50.7(±5.9) −39.1(±4.9) −29.7(±4.3) −26.4(±3.8) −22.0(±3.6) −16.9(±3.3) −13.2(±3.0)

1.000 1.013 1.019 1.025 1.030 1.034 1.042 1.047

43.86 43.46 43.32 43.17 43.04 42.93 42.79 42.66

−73.4 −39.7(±5.8) −28.0(±4.9) −21.9(±4.2) −16.2(±3.8) −13.2 (±3.5) −8.4 (±3.2) −5.6 (±3.0)

1.000 1.014 1.021 1.027 1.033 1.038 1.046 1.052

43.32 42.90 42.76 42.63 42.49 42.40

−58.7 −28.5(±5.7) −19.3(±4.8) −11.9(±4.1) −9.1(±3.7) −4.9(±3.4)

1.000 1.016 1.022 1.030 1.037 1.042

2

m ·N

−1

5



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Table 2. continued

m mol ·kg −1c

10−3ρ kg·m−3

u m·s−1

η mPa·s

0.089265 0.101740

1.006339 1.007656

1533.32 1534.60

0.770 0.776

0.000000 0.027913 0.040000 0.052690 0.065060 0.075000 0.089265 0.101740

0.994125 0.997496 0.998911 1.000371 1.001768 1.002856 1.004411 1.005722

1531.37 1535.22 1536.34 1537.63 1538.68 1539.72 1541.04 1542.23

0.666 0.677 0.684 0.689 0.694 0.698 0.704 0.709

106 ·Vϕ 3

−1

m ·mol

T = 308.15 K 273.81(±0.56) 274.72(±0.49) T = 313.15 K 269.05 271.20(±1.79) 271.94(±1.25) 272.66(±0.95) 273.35(±0.77) 274.12(±0.67) 274.88(±0.56) 275.76(±0.49)

1015·(κs) 2

m ·N

−1

1015·(κϕ) m ·N−1·mol−1 5

ηr

42.27 42.14

−0.6(±3.1) 1.3(±2.9)

1.050 1.059

42.89 42.54 42.41 42.28 42.16 42.06 41.92 41.80

−37.8 −16.1(±5.6) −7.1(±4.7) −3.1(±4.1) 1.4(±3.7) 2.7(±3.4) 5.2(±3.1) 7.0(±2.9)

1.000 1.017 1.027 1.035 1.042 1.048 1.057 1.065

a Standard uncertainties u are u(T) = 0.03 K; u(m) = 0.0001 mol·kg−1; u(p) = 10 kPa. bCombined expanded uncertainty Uρ(ρ) = 0.1 kg·m−3 (k = 2) ;Uu(u) = 1 m·s−1(k = 2); Uηr (ηr)= 0.02 (k = 2) with 0.95 level of confidence. cMolality (m) of ionic liquids for binary systems is incorporated as per kilogram of water and for the ternary system, the molality is reported as per kilogram of aqueous 0.06 mol·kg−1 glycine solution.

expanded uncertainty was found to be Uu(u) = 1 m·s−1. The uncertainty in relative viscosity was found to be ±0.01 and the combined expanded uncertainty for relative viscosity was found to be Uηr(ηr) = 0.02.23 The uncertainty in the molality u(m) of studied systems for DILs in binary and ternary systems were evaluated to be less than ±0.0001 mol·kg−1. The molality of ionic liquids for binary systems is incorporated as per kilogram of water and for the ternary system, the molality is reported as per kilogram of aqueous 0.06 mol·kg−1 glycine solution.

3. RESULTS AND DISCUSSION 3.1. Volumetric Properties. 3.1.1. Apparent Molar Volume. Experimental values of densities for the studied DILs, that is; [C(n)-DIL] where (n = 4, 5) in aqueous binaries and 0.06 mol·kg−1 aqueous glycine solutions with various molalities at T = (293.15 to 313.15) K are enlisted in Table 2. The graphical representation related to densities of binary systems as a function of molality with respect to the temperature (298.15, 303.15, and 308.15 K) is shown in Figure 1. For instance, our experimental values obtained for the density of glycine at 0.06 mol·kg−1 solution agreed well with the values as observed by Ivanov et al. at T = 298.15 and 308.15 K, Kumar et al. at T = 298.15 and 308.15 K, respectively.24,25 The literature comparisons for glycine and DILs have been incorporated in the form of graphical representation in the Supporting Information. It is revealed from the table that the densities of the studied ILs vary in order of C4 > C5 with the addition of solute, and growth in length of a carbon chain reduces with the rise in temperature of the DILs. Also, the same variations occurred in the case of all ternary systems. In general, the density of the compounds depends on how closely the ions are packed, the shape and size of the ions, the variety of cations and anions, and ion−ion interactions. Apparent molar volume is evaluated by expending the data of density for both studied systems using the equation:26 ÄÅ ÉÑ ÅÅÅ (ρ0 − ρ) ÑÑÑ M ÑÑ + ÅÅÅ Vϕ = ÅÅ mρρ ÑÑÑ ρ (1) 0 Ñ ÅÇ Ö

Figure 1. Plot of density(ρ) as a function of molality(m) for an aqueous solution of DILs shown by (green ▼−▼; pink ◀−◀; brown ▶−▶), C4−DIL; (blue ⧫−⧫; purple ⬟−⬟ red ⬢−⬢; ), C5-DIL at T = (298.15, 303.15, and 308.15) K, respectively.

In these equations, ρ and ρ0 are the densities in kg·m−3 of solution and solvent (water or water + glycine), M and m are the molar mass in kg·mol−1 and molality in mol·kg−1 of solute and solution, respectively. It provides valuable information regarding the nature of solute and solvent on the basis of ion− ion and ion−solvent interactions. The Vϕ values rise with the addition of solute in aqueous solutions of DILs and aqueous solutions of glycine with respect temperature are reported in Table 2. The uncertainties in Vϕ at 0.03 mol·kg−1 and 0.1 mol· kg−1 concentrations of binary solutions were found to be ≈1.46 × 10−6 m3·mol−1 and ≈4.48 × 10−7 m3·mol−1 for lower and higher concentrations of DILs. According to the tabular values, it can be attributed that an increase in the strength of interactions (solute−solvent) between DILs and glycine which specify expansion in electrostriction. An increase in Vϕ values of imidazolium-based ionic liquids with a concentration of glycine has been derived. The Redlich−Meyer relation is used to compute the apparent molar volume at infinite dilution solute (V0ϕ):27 F



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Figure 2. Plot of (Vϕ−AVm1/2 ) against molality (m) of aqueous solutions for DILs shown by yellow, blue, purple, red, and green balls, C4−DIL; and aqua, black, orange, blue, and red balls, C5−DIL, at T = (298.15, 308.15, and 313.15) K, respectively. .

Table 3. Limiting Apparent Molar Volume (V0ϕ), Experimental Slope (Sv), Limiting Apparent Molar Compressibility (κ0ϕ), Limiting Apparent Molar Expansivity (E0ϕ) at T = (298.15 and 308.15) K, (∂2V0ϕ/∂T2) at T = 303.15 K of Binary (DIL + Water) and Ternary (DIL + Water + Glycine) Systems 106 . V 0ϕ

T K

m 3. mol−1

Sv

293.15 298.15 303.15 308.15 313.15

244.39 245.48 246.72 247.80 248.88

25.29 24.10 22.15 20.21 18.34

293.15 298.15 303.15 308.15 313.15

265.49 266.14 267.16 267.96 268.82

37.45 40.11 38.47 38.15 36.48

293.15 298.15 303.15 308.15 313.15

247.36 247.98 248.42 248.94 249.60

28.09 27.62 28.59 27.71 25.87

293.15 298.15 303.15 308.15 313.15

265.69 266.68 267.36 268.10 269.20

52.20 52.78 57.44 57.85 57.08

Vϕ = V ϕ0 + AV m1/2 + S Vm

1015. κϕ0

106 . Eϕ0

∂ 2V ϕ0

m 5. N−1. mol−1

m 3. mol−1. K−1

∂T 2

C4-DIL + Water −69.9 −56.5 −42.8 −30.7 −17.3 C5-DIL + Water −73.4 −61.9 −50.3 −35.2 −18.2 C4-DIL + Water + Glycine −93.7 −66.5 −43.9 −31.2 −18.1 C5-DIL + Water + Glycine −99.7 −87.8 −73.5 −58.8 −37.8

0.233 −0.017 0.216

0.167 −0.001 0.166

0.106 0.012 0.118

0.167 0.017 0.184

In this equation V0ϕ is the volumetric behavior of solute on the basis of ion−solvent interactions in solutions obtained

(2) G



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locations includes the −OH, −CO, and −O− of glycine. These are heavily hydrated, and hydrophobic hydrations of alkyl (R) ions of DILs cause the dominance of the ion− hydrophilic interaction over the hydrophobic−hydrophobic interactions in the studied systems. Overall, the magnitudes of transfer volumes in the case of pentyl DIL are greater as compared to those observed in the case of butyl DILs. The positive partial molar volume of transfer in imidazolium-based ILs has been described in the literature.26 3.1.3. Limiting Apparent Molar Expansibilities. The limiting apparent molar expansivity (E0ϕ) has been estimated using V0ϕvalues via the following relation:

from infinite dilution. AV is the Debye-Hückel limiting slope which depends on valency and temperature. SV is the semiempirical or experimental slope of Vϕ -AVm1/2 against m. It provides the quantitative estimation of pairwise interaction that indicates stronger at positive and weaker at negative values for solutes in the system.28 Figure 2 represents the variation in Vϕ−AVm1/2 as a function of molality for studied DILs in an aqueous environment at all studied temperatures. The values of V0ϕ studied DILs in an aqueous environment and an aqueous solution of glycine at all studied temperatures are enlisted in Table 3. From the perusal of the table, the slope values of SV are positive and vary with rising temperature in the case of binary as well as in ternary systems. It is thus clear that both cations and anions act as water structure breakers. This indicates the presence of solute−solvent interactions in the studied systems. These solute−solvent interactions are further strengthened which varies with the increase in carbon chain length in imidazolium-based DILs. It is noticed that for the ternary system, V0ϕ values of studied DILs are slightly higher than corresponding binary systems. Moreover, the DILs with higher alkyl chain are less solvated by layers of water and therefore have more freedom to interact with glycine molecules.29 In other way, we can interpret that the IL cations are hydrophilic and hence cause more ion−solvent interactions. 3.1.2. Partial Molar Volume of Transfer. The partial molar volume of transfer (ΔtrV0ϕ) at infinite dilution of DILs from water to 0.06 mol·kg−1 aqueous solution of glycine has been calculated by using the values of V0ϕ as follows: Δtr V ϕ0 = V ϕ0(aqglycine) − V ϕ0(water)

Eϕ0 = (∂V ϕ0 /∂T )

The calculated values of for DILs in binary and ternary at T = 298.15, 303.15, and 308.15 K are listed in Table 3. It is observed that E0ϕ values for DILs in the studied solutions are positive and decrease with a rise in temperatures from butyl to pentyl DILs in both binary systems. In the case of ternary systems E0ϕ values are positive and increase with a rise in temperature. A second order derivative of V0ϕ at infinite dilution with respect to temperature is another important thermodynamic parameter proposed by Hepler:30,31 ÄÅ 0 ÉÑ ÄÅ 2 0 ÉÑ ÅÅ ∂E ÑÑ ÅÅ ∂ V ÑÑ ϕÑ ÅÅ ϕ ÑÑ ÅÅ ÑÑ ÅÅ Ñ=Å ÅÅ ∂T ÑÑÑ ÅÅÅ ∂T 2 ÑÑÑ ÅÇ ÑÖ ÑÖ ÅÇ (5) The values of ∂2V0ϕ/∂T2 at T = 303.15 K are collected in Table 3. These provide the qualitative information on (Cosmotropes) structure−makers when ∂2V0ϕ/∂T2 is positive and (Chaotropes) structure−breakers when ∂2Vϕ0 /∂T2is negative for solutes in solutions. It is noted that the ∂2V0ϕ/ ∂T2values are negative which implies the studied DILs are chaotropes for binary (water + DILs) system and cosmotropes in ternary (water + DILs + glycine) systems due to positive values of ∂2V0ϕ/∂T2.32,33 3.2. Ultrasonic Properties. 3.2.1. Speed of Sound. The speed of sound (u) with derived parameters allows us to distinguish the behavior of thermodynamic features of molecular interactions. Values of the speed of sound are listed in Table 2. Figure 3 represents the behavior of speed of sound (u) for DILs plotted against molality (m) at T = 298.15, 303.15, and 308.15 K. It implies that u increases over the order C4 < C5 DILs with the addition of solutes and rises with a rise in temperature over the studied range. Here, the speed of sound increases with a rise in alkyl chain length due to the increase in molecular interactions in imidazolium cations, anions, and hydroxyl groups found in studied systems. Our results for glycine solutions in 0.06 mol·kg−1 agree well with those of Kumar et al. at T = 298.15 and 308.15 K. The literature comparison in the form of graphical representation has been given in Supporting Information.34 Isentropic compressibility (κs) has been evaluated based on density and speed of sound data for DILs using the Newton− Laplace equation:

(3)

where the values of ΔtrV0ϕ being recruited in Table 4. It is found to be positive and varies with the concentration of solutes with respect to temperature. This behavior of possible interactions was deduced with the help of the cosphere overlap model by Gurney, Franks, and Evans.26 According to this model, the overlapping of hydration cospheres in hydrophilic Table 4. Transfer Partial Molar Properties ΔtrV0ϕ, Δtrκ0ϕ and ΔtrB of Butyl (C4) and Pentyl (C5) Ternary (DIL + Water + Glycine) Systems at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K DILs

T/K = 293.15

T/K = 298.15

T/K = 303.15

T/K = 308.15

T/K = 313.15

2.97

m 3·mol−1 2.50 1.70

1.14

0.72

0.20

0.54

0.14

0.38

−0.46

−0.70

−23.60

−19.63

106Δtr Vϕ 0 C4DIL C5DIL

0.20

1015Δtr κϕ 0 C4DIL C5DIL

−23.84 −26.26

m 5·N −1·mol−1 −9.97 −1.15 −25.89

−23.20

1 i ∂V y 1 κs = − jjj zzz = V k ∂P {S ρu 2

103(Δtr B) m 3·mol−1 C4DIL C5DIL

0.026

0.010

0.015

0.020

0.011

0.021

0.016

0.020

0.016

0.018

(4)

E0ϕ

(6)

The isentropic compressibility (κs) values are incorporated in Table 2. It decreases with increasing concentrations with increase in temperature. It also decreases with increasing alkyl chain length from butyl to pentyl DILs in the studied systems. H



Article

variation in calculated values of κ0ϕ is tabulated in Table 3. From the tabular values, it is noticed that κ0ϕ values are negative and increase with a rise in alkyl chain length and decrease from binary to the ternary system with respect to the temperature. This type of phenomenon occurs because of greater resistance to pressure of the ordered form of solvent. It may be due to the water structure that is less compressible around the solute molecules as compared to molecules of water in bulk which is accredited to the dominance of attractive interactions in DILs and amino acid.37 3.2.3. Partial Molar Compressibility of Transfer. Values of apparent molar isentropic compressibility of infinite dilution are used to estimate the partial molar compressibility of transfer (Δtrκ0ϕ) using the following equation: Δtr κϕ0 = κϕ0(aqglycine) − κϕ0(water)

where Δtrκ0ϕ values are found to be negative in aqueous solutions of glycine which are incorporated in Table 4. Usually, the magnitudes of Δtrκ0ϕ values having a nonlinear trend with a concentration of each imidazolium-based DILs has been observed at a temperature that can be discussed by considering the structural interaction model.26,38 It suggests that the ions get heavily hydrated causing a decrease in compressibility.39 3.3. Transport Properties. 3.3.1. Relative Viscosity. Viscometric studies provide valuable information regarding ion−ion and ion−solvent interactions and can support the resulting values of volumetric properties. The experimental data of absolute viscosities (η) in water and aqueous solutions of glycine at experimental temperatures have been described in Table 2. It is clear from the enlisted tabular values that the viscosity of the studied solution increases with the addition of ionic liquids and reduces with the rise in temperatures in both studied systems. It is observed that for pentyl DIL the viscosity values are higher than the ones in butyl DIL with the order of C5 > C4. The relative viscosities (ηr) have been analyzed by applying the Jones−Dole equation for studied DILs:40,41

Figure 3. Variation in the speed of sound (u) is plotted against molality (m) for the aqueous solutions of DILs shown by black ■−■; red ●−●; blue ▲−▲), C4−DIL; green ▼−▼; pink ◀−◀; brown ▶−▶, C5−DIL at T = (298.15, 303.15, and 308.15) K, respectively.

This is because the available free space increases between solute and solvent molecules.35 3.2.2. Apparent Molar Isentropic Compressibility. Apparent molar isentropic compressibility was also evaluated to understand the intermolecular interactions by the following equation: ÄÅ É ÅÅ (ρ κs − ρκ0) ÑÑÑ ÄÅÅÅ Mκ ÉÑÑÑ ÅÅ 0 ÑÑ ÅÅ s ÑÑ κϕ = ÅÅ ÑÑ + ÅÅ ÅÅ ÑÑ ÅÅÇ ρ ÑÑÑÑÖ ρρ m (7) 0 ÅÇ ÑÖ where ρ and ρ0 are densities in kg·m−3 of solution and solvent (water or water + glycine), M and m are the molar mass in kg· mol−1 and molality in mol·kg−1 of the solute (DILs), κs and κ0 are the isentropic compressibilities of the solution and solvent, respectively. The calculated values of apparent molar isentropic compressibility (κϕ) have been recruited in Table 2. Uncertainty in κϕ values by considering the speed of sound (u) as ±0.5 m·s−1 and the isentropic compressibility (κs) to be ±0.03 × 10−11 m2·N−1, the uncertainties in κϕ at 0.03 and 0.1 mol·kg−1 concentrations of binary solutions were found to be ±5.06 × 10−15 m5·N−1·mol−1 and ±3.03 × 10−15 m5·N−1· mol−1. From the tabular values, it concludes that the magnitudes of κϕvalues are less negative and reduce with the rise in concentration at a particular temperature in the studied systems. The decrease in κϕ values are due to thermal rupture of the water structure around the substituted imidazolium cations in DILs and hydroxyl groups (−OH) present in glycine which raises the solute−solvent interactions.36 The variation in apparent molar isentropic compression at infinite dilution (κ0ϕ) were estimated by the least-squares fitting method: κϕ = κϕ0 + Sκm1/2

(9)

ηr = 1 + A C + BC + DC 2

(10)

In these equations, the Falkenhagen coefficient A signifies the ion−ion interionic forces. The Jones−Dole viscosity B coefficient concerns the hydration of solute within the solution and it is related to shape and sizes of solute and co-solutes. It is calculated by fitting the viscosity data in the least-square method. From tabular values, it is observed that the viscosity A coefficient is positive and quite sensitive to temperature for studied solutions. The values of positive viscosity B coefficients indicate that the cations act as electrostrictive structure maker but causes the overall water structure breaking as dB/dT is positive. Generally, bulky particles exhibit greater viscosity B coefficients for solutes which may not be revealing specifically for bulky hydrophobic interactions.42,43 The values of dB/dT for the studied DILs are computed in Table 5. The coefficient D represents the solute−solute structural interactions and to some extent higher terms of Columbic forces. Also, it represents the cation−anion−cation triplet (superexchange interaction) interaction and the Columbic higher order hydrodynamic effect contribution. 3.3.2. Viscosity B Coefficient of Transfer. The viscosity B coefficients of transfer (ΔtrΒ) from water to aqueous glycine systems have been estimated as

(8)

In this equation, Sκ is the experimental slope and suggests the nature of solute−solute interactions. The smooth extrapolation of κϕ against the molality (m)1/2 curve to zero concentration yields the values of limiting apparent molar compressibility of the solute (κ0ϕ). The κ0ϕ implies the interactions takes place in the solute with the solvents in which the presence of solute− solvent interactions is invalidated on infinite dilution. The

Δtr B = B(aqglycine) − B(water) I

(11) DOI: 10.1021/acs.jced.8b00349 J. Chem. Eng. Data XXXX, XXX, XXX−XXX


Article

Table 5. A, B, and D Viscosity Coefficients, The Temperature Coefficient of B, i.e., (dΒ/dT) at T = (298.15 and 308.15) K of Binary and Ternary Systems at Different Temperatures T = (293.15, 298.15, 303.15, 308.15 and 313.15) K T K 293.15 298.15 303.15 308.15 313.15 293.15 298.15 303.15 308.15 313.15 293.15 298.15 303.15 308.15 313.15 293.15 298.15 303.15 308.15 313.15

A (dm 3·mol−1)1/2

B dm 3·mol−1

D (dm 3·mol−1)2

C4-DIL + Water 0.133 0.138 0.147 0.172 0.195 C5-DIL + Water 0.049 0.170 0.045 0.164 0.053 0.186 0.055 0.172 0.061 0.269 C4-DIL + Water + Glycine 0.039 0.159 0.041 0.148 0.046 0.162 0.051 0.192 0.046 0.206 C5-DIL + water + glycine 0.047 0.191 0.044 0.181 0.045 0.206 0.057 0.188 0.052 0.287 0.051 0.056 0.062 0.074 0.087

dB dT

1.471 1.513 1.815 1.887 1.455

0.003

1.693 1.951 2.246 2.567 2.310

0.005

Figure 4. Comparative thermogravimetric curve for shown by (blue ), C4−DIL; (red ), C5−DIL with scan rate 10 °C·min−1.

2.346 2.091 2.218 2.307 2.086

0.002

1.973 1.674 1.959 2.357 2.310

0.005

Columbic interactions existing between species of a higher charge.1 3.5. Electrochemical Window. To the application route, the electrochemical properties of the synthesized DILs were investigated using cyclic voltammetry curves. The three electrode electrochemical setup was used to measure the cyclic voltammetry curve in which Ag/AgCl is a reference electrode, platinum wire is a counter electrode, and dip and dry coated multiwalled carbon nanotubes (MWCNTs) over a stainless steel (Supporting Information) substrate form the working electrode.49,50 Besides, as prepared DILs were used as an electrolyte prepared at the same concentration of 0.1 M in Millipore water. Figure 5 shows CV curves in different DIL

The values of ΔtrΒ are incorporated in Table 4. They are positive due to the higher values of B coefficients for the studied DILs in both studied systems. These values vary with an increase in concentrations at all experimental temperature. It can be seen from the table that ΔtrΒ values are positive and vary in rising with temperature from butyl to pentyl DILs which determines that the ion−hydrophilic interactions are less dominant over the ion−hydrophobic interactions in the studied systems. These interactions are further strengthened with addition of the solutes with aqueous glycine solution. Similar results have been reported in the literature.44,45 3.4. Thermogravimetric Analysis. The thermal stability of synthesized DILs has been discussed in terms of decomposition temperature (Td) which is shown in Figure 4. The thermal stability was evaluated by moderate thermogravimetric analysis (TGA) scans with a heating rate of 10 °C· min−1. From the figure, it can be seen that the decomposition temperature is noted as when the initial mass derivative stretches to the deepest value. It also can be observed that the thermal stability depends on the nucleophilicity of the bromide ions (coordinating nature of anion) which decreases the stability of the cations with respect to temperature.46 This is because as the alkyl chain length plays an important role and positively charged present nitrogen stabilizes the cation, the decomposition in imidazolium and pyridinium at C−N bonds occurs.47 Usually, melting temperature increases with an increase in alkyl chain length (butyl < pentyl) for cations and anion sizes which is described already in the case of the series of iodide salts in the literature.48 Dicationic ionic liquids are more viscous than monocationic ones due to stronger

Figure 5. Cyclic voltammetry curve of studied DILs: (blue ), C4− DIL; (red ), C5-DIL electrolytes at a constant scan rate of 50 mV/s within the potential range of 0 to 0.9 V for CNT thin film electrode.

electrolytes at a constant scan rate of 50 mV/s within the potential range of 0 to 0.9 V. Ideally, carbon-based working electrodes exhibit a rectangular CV shape which means a linear variation of current with respect to voltage.50,51 Interestingly, the MWCNTs electrode shows such a rectangular CV shape at 50 mV/s scan rate in different DILs electrolytes, suggesting J



Article

(4) Carda-Broch, S.; Berthod, A.; Ruiz-Angel, M. J. Ionic Liquids in Separation Techniques. J. Chromatogr. A 2008, 1184, 6−18. (5) Wilkes, J. S.; Levisky, J. A.; Wilson, R. A.; Hussey, C. L. Dialkylimidazolium Chloroaluminate Melts: A New Class of Room− Temperature Ionic Liquids for Electrochemistry, Spectroscopy and Synthesis. Inorg. Chem. 1982, 21, 1263−1264. (6) Wilkes, J. S.; Zaworotko, M. J. Air and Water Stable 1-ethyl-3methylimidazolium Based Ionic Liquids. J. Chem. Soc., Chem. Commun. 1992, 965−967. (7) Plechkova, N. V.; Seddon, K. R. Applications of Ionic Liquids in the Chemical Industry. Chem. Soc. Rev. 2008, 37, 123−150. (8) Giernoth, R. Task−Specific Ionic Liquids. Angew. Chem., Int. Ed. 2010, 49, 2834−2839. (9) Huddleston, J. G.; Willauer, H. D.; Swatloski, R. P.; Visser, A. E.; Rogers, R. D. Room Temperature Ionic Liquids as Novel Media for ‘Clean’ Liquid−Liquid Extraction. Chem. Commun. 1998, 1765. (10) Elyasi, M.; Khalilzadeh, M. A.; Karimi-Maleh, H. High Sensitive Voltammetric Sensor Based on Pt/CNTs Nanocomposite Modified Ionic Liquid Carbon Paste Electrode for Determination of Sudan I in Food Samples. Food Chem. 2013, 141, 4311−4317. (11) Zhang, H.; Qi, S.; Dong, Y.; Chen, X.; Xu, Y.; Maa, Y.; Chen, X. A Sensitive Colorimetric Method for the Determination of Nitrite in Water Supplies, Meat and Dairy Products Using Ionic Liquid− modified methyl red as a color reagent. Food Chem. 2014, 151, 429− 434. (12) Toniolo, R.; Pizzariello, A.; Dossi, N.; Lorenzon, S.; Abollino, O.; Bontempelli, G. Room Temperature Ionic Liquids as Useful over Layers for Estimating Food Quality from their odor Analysis by Quartz Crystal Microbalance Measurements. Anal. Chem. 2013, 85, 7241−7247. (13) Fang, D.; Yang, J.; Jiao, C. Dicationic Ionic Liquids as Environmentally Benign Catalysts for Biodiesel Synthesis. ACS Catal. 2011, 1, 42−47. (14) Payagala, T.; Huang, J.; Breitbach, Z. S.; Sharma, P. S.; Armstrong, D. W. Unsymmetrical Dicationic Ionic Liquids: Manipulation of Physicochemical Properties using Specific Structural Architectures. Chem. Mater. 2007, 19, 5848−5850. (15) Freire, M. G.; Teles, A. R. R.; Rocha, M. A. A.; Schroder, B.; Neves, C. M. S. S.; Carvalho, P. J.; Evtuguin, D. V.; Santos, B. F.; Coutinho, A. P. Thermophysical Characterization of Ionic Liquids able to Dissolve Biomass. J. Chem. Eng. Data 2011, 56, 4813−4822. (16) Eshetu, G. G.; Armand, M.; Scrosati, B.; Passerini, S. Energy Storage Materials Synthesized from Ionic Liquids. Angew. Chem., Int. Ed. 2014, 53, 2−20. (17) Carneiro, A. P.; Held, C.; Rodriguez, O.; Sadowski, G.; Macedo, E. A. Solubility of Sugars and Sugar Alcohols in Ionic Liquids: Measurement and PC−SAFT Modeling. J. Phys. Chem. B 2013, 117, 9980−9995. (18) Sun, N.; Rodriguez, H.; Rahman, M.; Rogers, R. D. Where are Ionic Liquid Strategies most suited in the Sursuit of Chemicals and Energy from Lignocellulosic Biomass? Chem. Commun. 2011, 47, 1405−1421. (19) Gardas, R. L.; Dagade, D. H.; Coutinho, A. P.; Patil, K. J. Thermodynamic Studies of Ionic Interactions in Aqueous Solutions of Imidazolium−Based Ionic Liquids [emim][Br] and [bmim][Cl]. J. Phys. Chem. B 2008, 112, 3380−3389. (20) Chen, Y.; Zhuo, K.; Chen, J.; Bai, G. Volumetric and viscosity properties of dicationic ionic liquids in (glucose + water) Solutions at T = 298.15 K. J. Chem. Thermodyn. 2015, 86, 13−19. (21) Nachtigall, F. M.; Corilo, Y. E.; Cassol, C.; Ebeling, G.; Morgon, N. H.; Dupont, J.; Eberlin, M. N. Multiply Charged (Di−) Radicals. Angew. Chem., Int. Ed. 2008, 47, 151−154. (22) Anderson, J. L.; Ding, R.; Ellern, A.; Armstrong, D. W. Structure and Properties of High Stability Geminal Dicationic Ionic Liquids. J. Am. Chem. Soc. 2005, 127, 593−604. (23) Kawadkar, D. V.; Pratap, U. R.; Wankhade, A. V.; Zodape, S. P. Influence of D−glucose on solvation behavior of bis C3 (mim) br2. J. Mol. Liq. 2017, 232, 94−104.

that DILs can be an ideal candidate toward the use of an electrolyte for energy storage application.

4. CONCLUSIONS Volumetric, acoustic and viscometric properties of aqueous and ternary aqueous solutions containing dicationic ionic liquids and glycine have been studied. The experimental data of densities, speed of sound, and relative viscosities are used to obtain derived properties such as apparent molar volume, apparent molar isentropic compressibility, and the viscosity B coefficient for synthesized DILs. Further, apparent molar volume and apparent molar isentropic compressibilities at infinite dilution for the estudied systems were found by using the Redlich−Mayer type equation. It suggested on the basis of positive SV values (slope values for volume concentration plot), large negative apparent molar isentropic compressibility, and positive viscosity B coefficient with positive dB , that DILs acts dT as water structure breaking electrolytes, the extent of which increases with a rise in temperature. There is a predominance of hydrophilic centers and water molecules interactions which are not compensated by hydrophobic moieties present in the molecule. Thus, in binary solutions, these electrolytes (specially the cations) act as chaotropes. The extent of chaotropism is attenuated in ternary solutions containing glycine which is also known for its chaotropic action with solvent water.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b00349. The standard and combined expanded uncertainties for the data entries of Table 2 measured using the digital density and sound velocity meter (make, Anton Paar; model, DSA 5000M) (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Sangesh P. Zodape: 0000-0002-7283-902X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors wish to thanks Prof. K. J. Patil, Dr. Vasim Shaikh, Dr. Swapnil Karade, Prabhakar Shrivas, and Vidyasagar Devthade for their help in improving the manuscript.

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REFERENCES

(1) Hojniak, S. D.; Khan, A. L.; Holloczki, O.; Kirchner, B.; Vankelecom, F. J.; Dehaen, W.; Binnemans, K. Separation of Carbon Dioxide From Nitrogen or Methane by Supported Ionic Liquid Membranes (SILMs): Influence of the Cation Charge of the Ionic Liquid. J. Phys. Chem. B 2013, 117, 15131−15140. (2) Sun, P.; Armstrong, D. W. Ionic liquids in Analytical Chemistry. Anal. Chim. Acta 2010, 661, 1−16. (3) Bonhôte, P.; Dias, A. P.; Armand, M.; Papageorgiou, N.; Kalyanasundaram, K.; Grätzel, M. Hydrophobic, Highly Conductive Ambient−Temperature Molten Salts. Inorg. Chem. 1996, 35, 1168− 1178. K



Article

(24) Ivanov, E. V.; Lebedeva, E. Y. Effect of Temperature on volumetric behavior of glycine in aqueous mebicar (N−tetramethylglycoluril) at p ∼ 0.1 MPa. J. Mol. Liq. 2017, 242, 235−243. (25) Kumar, H.; Behal, I. Volumetric, ultrasonic and UV absorption studies on interactions of antibiotic drug Chloramphenicol with Glycine and its Dipeptide in aqueous solutions at T = (288.15− 318.15) K. J. Chem. Thermodyn. 2016, 99, 16−29. (26) Jin, H. X.; Chen, H. Y. Volumetric Properties of 1−butyl−3− methylimidazolium Tetrafluoroborate−Glucose−Water Systems. J. Chem. Eng. Data 2012, 57, 1134−1138. (27) Greaves, T. L.; Drummond, C. J. Protic Ionic Liquids: Evolving Structure−Property Relationships and Expanding Applications. Chem. Rev. 2008, 108, 206−237. (28) Taboada, P.; Attwood, D.; Ruso, J. M.; Garcia, M.; Mosquera, V. Thermodynamic Properties of some Antidepressant Drugs in Aqueous Solution. Langmuir 2001, 17, 173−177. (29) Desnoyers, J. E.; Arel, M.; Perron, G.; Jolicoeur, C. Apparent Molal Volumess of Alkali Halides in Water at 25 °C. Influence of Structural Hydration Interactions on the Concentration Dependence. J. Phys. Chem. 1969, 73, 3346−3351. (30) Hakin, A. W.; Copeland, A. K.; Liu, J. L.; Marriott, R. A.; Preuss, K. E. Densities, Apparent Molar Volumes and Apparent Molar Heat Capacities of l−arginine, l−proline and 1−methionine in Water at 288.15, 298.15, 313.15, and 328.15 K. J. Chem. Eng. Data 1997, 42, 84−89. (31) Hepler, G. Thermal Expansion and Structure in Water and Aqueous Solutions. Can. J. Chem. 1969, 47, 4613−4617. (32) Gutierrez-Pichel, M. G.; Taboada, P.; Varela, L. M.; Attwood, D.; Mosquera, V. Solute and Solvent Structure Effects on the Volume and Compressibilities of some Colloidal Penicillins in Aqueous Solution. Langmuir 2002, 18, 3650−3654. (33) Cabani, S.; Conti, G.; Matteoli, E. Partial Molal Expansibilities of Organic Compounds in Aqueous Solution. J. Solution Chem. 1976, 5, 751−763. (34) Kumar, H.; Singla, M.; Jindal, R. Interactions of glycine, L− alanine and L−valine with aqueous solutions of Trisodium Citrate at different temperatures: A volumetric and acoustic approach. J. Chem. Thermodyn. 2013, 67, 170−180. (35) Capelo, S. B.; Mendez-Morales, T. M.; Carrete, J.; Lopez-Lago, E. L.; Vila, J.; Cabeza, O.; Rodriguez, J. R.; Turmine, M.; Varela, L. M. Effect of Temperature and Cationic Chain Length on the Physical Properties of Ammonium Nitrate−Based Protic Ionic Liquids. J. Phys. Chem. B 2012, 116, 11302−11312. (36) Cheema, M. A.; Barbosa, S.; Taboada, P.; Castro, E.; Siddiq, M.; Mosquera, V. A. A Thermodynamic Study of the Amphiphilic Phenothiazine Drug Thioridazine Hydrochloride in Water/Ethanol Solvent. Chem. Phys. 2006, 328, 243−250. (37) Bhat, R.; Kishore, N.; Ahluwalia, J. C. Thermodynamic Studies of Transfer of some Amino Acids and Peptides from Water to Aqueous Glucose and Sucrose Solutions at 298.15 K. J. Chem. Soc., Faraday Trans. 1 1988, 84, 2651−2665. (38) Singh, V.; Chhotaray, P. K.; Gardas, R. L. Modulation of volumetric properties of D (+)−glucose in aqueous 3−hydroxypropylammonium Acetate solutions. J. Mol. Liq. 2016, 220, 150−154. (39) Bhattacharya, D. M.; Kawadkar, D. V.; Pandhurnekar, C. P.; Wankhade, A. V.; Pratap, U. R.; Zodape, S. P. Investigation of Volumrteic and Acoustic Properties of Procainamide Hydrochloride in Aqueous Binary and (Water + Amino acid) Ternary Mixtures at Different Temperatures. J. Chem. Eng. Data 2017, 62, 4083−4092. (40) Jones, G. The Viscosity of Aqueous Solutions of Strong Electrolytes with Special Reference to Barium Chloride. J. Am. Chem. Soc. 1929, 51, 2950−2964. (41) Bakker, H. J. Structural Dynamics of the Aqueous Salt Solution. Chem. Rev. 2008, 108, 1456−1473. (42) Shekaari, H.; Kazempour, A. Density and Viscosity in Ternary D−xylose + Ionic Liquid (1−alkyl−3−methylimidazolium Bromide) + Water Solutions at 298.15 K. J. Chem. Eng. Data 2012, 57, 3315− 3320.

(43) Sarma, T. S.; Ahluwalia, J. C. Experimental Studies on the Structure of Aqueous Solutions of Hydrophobic Solutes. Chem. Soc. Rev. 1973, 2, 203−232. (44) Banipal, P. K.; Singh, V.; Aggarwal, N.; Banipal, T. S. Hydration Behavior of some Mono−, Di−, and Tri−saccharides in Aqueous Sodium Gluconate Solutions at T= (288.15, 298.15, 308.15 and 318.15) K: Volumetric and Rheological Approach. Food Chem. 2015, 168, 142−150. (45) Breslau, B.; Miller, I. On the Viscosity of Concentrated Aqueous Electrolyte Solutions. J. Phys. Chem. 1970, 74, 1056−1061. (46) Patil, R. A.; Talebi, M.; Bhawal, S. S.; Armstrong, D. W. Synthesis of Thermally Stable Geminal Dicationic Ionic Liquids and Related Ionic Compounds: an Examination of Physicochemical Properties by Structural Modification. Chem. Mater. 2016, 28, 4315−4323. (47) Huddleston, J. G.; Visser, A. E.; Reichert, W. M.; Willauer, H. D.; Broker, G. A.; Rogers, R. D. Characterization and Comparison of Hydrophilic and Hydrophobic Room Temperature Ionic Liquids Incorporating the Imidazolium Cation. Green Chem. 2001, 3, 156− 164. (48) Adamová, G.; Gardas, R. L.; Nieuwenhuyzen, M.; Puga, A. V.; Rebelo, N.; Robertson, A. J.; Seddon, K. R. Alkyltributylphosphonium Chloride Ionic Liquids: Synthesis, Physicochemical Properties and Crystal Structure. Dalton Trans 2012, 41, 8316−8332. (49) Karade, S. S.; Dubal, D. P.; Sankapal, B. R. Decoration of Ultrathin MoS2 Nanoflakes over MWCNTs: Enhanced Supercapacitive Performance through Electrode to Symmetric All−Solid− State Device. Chemistry Select 2017, 2, 10405−10412. (50) Karade, S. S.; Sankapal, B. R. Room Temperature PEDOT: PSS Encapsulated MWCNTs Thin Film for Electrochemical Supercapacitor. J. Electroana. Chem. 2016, 771, 80−86. (51) Wang, Q.; Yan, J.; Fan, Z. Carbon Materials for High Volumetric Performance Supercapacitors: Design, Progress, Challenges and Opportunities. Energy Environ. Sci. 2016, 9, 729−762.

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Thermophysical Properties of Dicationic Ionic Liquids under the

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