Interaction of gluconate-based ionic liquids with common solvents: A study of volumetric, viscosity and conductivity properties

Interaction of gluconate-based ionic liquids with common solvents: A study of volumetric, viscosity and conductivity properties

Journal of Molecular Liquids 223 (2016) 1013–1020 Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsev...

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Journal of Molecular Liquids 223 (2016) 1013–1020

Contents lists available at ScienceDirect

Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq

Interaction of gluconate-based ionic liquids with common solvents: A study of volumetric, viscosity and conductivity properties Yujuan Chen, Qian Yang, Jing Chen, Guangyue Bai, Kelei Zhuo ⁎ Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, PR China

a r t i c l e

i n f o

Article history: Received 22 June 2016 Received in revised form 10 August 2016 Accepted 6 September 2016 Available online 10 September 2016 Keywords: Gluconate-based ionic liquids Limiting apparent molar volume Viscosity Limiting molar conductivities

a b s t r a c t With the intensive research of ionic liquids, more and more shortcomings of ionic liquids have been gradually found. At the same time, more ionic liquids with specific or multifunctional properties need to be designed for their wide applications. Thereby, the research for seeking new families of functionalized ionic liquids has been a hot topic. In this paper, we firstly synthetized seven novel functionalized gluconate-based ionic liquids [Cnmim][C6H11O7] (GBILs, n = 2, 4, 6, 8, 10, 12, and 14). Meanwhile, the volumetric, viscosity and conductivity properties for the GBIL + solvent (water/ethanol/propyl alcohol) systems were studied. The interactions between the ionic liquids and solvents were also explored. The results indicated that the interactions between the studied ILs and solvent depend on the structures of GBILs and the category of solvents. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Ionic liquids (ILs) usually consist of relatively larger organic cations and smaller inorganic anions, and can stay liquid state over a wide temperature rang. In the past few decades, ILs have been widely used due to their unique physical characteristics such as low volatility, large liquid range, and good electrical conductivity. What's more, they have provided unlimited opportunities to the researchers from all branches for further exploration [1]. The expedition showed that ILs have amazing applicability in the fields as solvent medium [2,3], extraction agent [4], biomass processing [5], petroleum refining [6], viscosity modifiers [7], magnetic fluid [8], SO2 capture agent [9], and precursors for highly luminescent [10]. For the reasons mentioned above, ILs have been named “Green products” [11] and constantly take steps into people's life. Although, numerous promising results have been harvested, their extensive use in process chemistry is still hampered by doubts related to the following drawbacks: (1) possible toxicological concerns, (2) problems related to product separation [12]. Thus, the concept of functionalized ionic liquids, so-called Task-Specific ILs (TSILs), has been proposed. Gluconic acid (GA) is a mild organic acid with the structure HOCH2(CHOH)4COOH, which is full of hydroxyl groups. It can be produced by biochemical oxidation of glucose, and shows the potential of synthesis through oxidizing glucose with oxygen or air by heterogeneous catalysts [13]. Due to the renewable and green production process, GA is always regarded as one of cheap and easily available biobased chemicals. ⁎ Corresponding author. E-mail address: [email protected] (K. Zhuo).

http://dx.doi.org/10.1016/j.molliq.2016.09.022 0167-7322/© 2016 Elsevier B.V. All rights reserved.

In view of the above facts, we choose gluconate anion (GA−) to prepare seven novel functionalized ILs (see Fig. 1). It is believed that these new-type ILs could be good candidates to overcome above two shortcomings. On the one hand, GA is characterized of biobased chemicals, largely available raw material, and green production process, and all these features make it to be highly praised as a low toxicity chemical. On the other hand, GA− anion is rich of a large number of hydroxyl groups, which makes gluconate-based ionic liquids [Cnmim][C6H11O7] (GBILs, n = 2, 4, 6, 8, 10, 12 and 14) high hydrophilic and immiscible with non-polar organic solvents. Consequently, easy separation process is realized by extraction. Based on the advantages mentioned above, we believe that GBILs will play important roles in chemistry and chemical engineering. So thermodynamic and transport properties of GBILs-solvents are required urgently, such as density, viscosity, conductivity, transport numbers, diffusion coefficients, and activity coefficients [13]. In this work, volumetric, viscosity and conductivity properties for GBIL + solvent (water/ethanol/propyl alcohol) systems were studied. The influence of the alkyl chain length of cations, the nature of the solvents, and the kind of GBILs anions on infinite dilute apparent molar volumes, viscosities B-coefficients, and the limiting molar conductivities were discussed.

2. Experimental 2.1. Chemicals The purities of the chemicals used in this work are presented in Table A1. All reagents were used without further purification. The

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Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020

n

n

Fig. 1. Chemical structures of [Cnmim][C6H11O7] (n = 2, 4, 6, 8, 10, 12, and 14).

doubly distilled water with a conductivity of (0.8–1.0 × 10−6 S cm−1) used throughout the experiments was got by automatic dual water distiller (SZ-93, Shanghai Rongsheng Chemical Instrument Company). 2.2. Preparation of [Cnmim][C6H11O7](n = 2, 4, 6, 8, 10, 12, and 14) 1-Alky-3-methylimidazolium hydroxide [Cnmim][OH] (n = 2, 4, 6, 8, 10, 12, and 14) ILs were prepared and purified using the procedure described previously in the literature [14,15]. Then the obtained [Cnmim][OH] were neutralized by D-gluconic acid solution, and the water was removed at 70 °C. The resulting products were dried at 50 °C to obtain final GBILs. Water content in GBILs found by the Karl Fischer method was b 0.001 in mass fraction. The obtained GBILs have purities of N 0.99 in mass fraction. The GBILs were analyzed by 1H NMR (Brucker AV-400 MHz) to confirm the absence of any major impurities (see Table A2).

The intrinsic volume of propyl alcohol is larger than methanol, so the solvent-structure reaction volume [19] of propyl alcohol is larger than methanol. This is why the limiting apparent molar volumes of GBILs in propyl alcohol are larger than in methanol. In other words, the limiting apparent volumes are affected not only by the interaction between solutes and solvents, but also by the nature of solvents. A linear relationship is observed between V0Φ,IL and n (the number of methylene groups in the alkyl chain of the cations, see Fig. 2). V 0Φ;IL ¼ V 0Φ;½C0 mim½C6 H11 O7  þ V 0Φ;CH2 nCH2

ð3Þ

The experimental temperature was controlled at 298.15 ± 0.01 K. The detailed measurements and instrumentations for densities, viscosities, and conductivities have been described elsewhere [11,16,17].

where VΦ , CH20 represents the contribution per methylene group (\\CH2) in the alkyl chains of the cations to the limiting apparent molar volumes. The obtained VΦ , CH20 values are included in Table 2. It can be seen that VΦ , CH20 values are also in the order: VΦ ,CH20(methanol) b VΦ , CH20(propyl alcohol) b VΦ ,CH20(water). Hydrophobic groups in water can promote the formation of hydrogen bonds between water molecules, so the VΦ , CH20 values in water are larger than those in alcohol. The intrinsic volume of propyl alcohol is much larger than methanol, so the solvent-structure reaction volumes [19] of GBILs in propyl alcohol are much larger than in methanol, which finally leads to larger VΦ,CH20 values in propyl alcohol.

3. Results and discussion

3.2. Viscosity

3.1. Limiting apparent molar volume

Viscosity is one of the important transport properties of the solution. The viscosities obtained are summarized in Table A4. The relative viscosities of the studied systems, ηr, can be analyzed using the JonesDole equation [20]

2.3. Measurements of densities, viscosities, and conductivities

Densities of solutions are included in Table A3. The apparent molar volumes of GBILs in water were calculated using the densities of solution ρ and solvent ρ1 by the following equation: V Φ;IL

MIL 1000ðρ−ρ1 Þ ¼ − ρ mIL ρρ1

ð1Þ

In lower concentration range, the apparent molar volumes used to describe the above equation are replaced by limiting apparent molar volumes V0Φ,IL whose values are the same as the standard partial molar volumes, which are usually obtained from equation: 1=2

V Φ;IL ¼ V 0Φ;IL þ SV mIL þ bV mIL

ð2Þ

where SV is the Debye-Hückel limiting law coefficient, and bv is an adjustable parameter that is related to the pair interactions and equals to the second virial coefficient in value [18]. The values of the apparent molar volumes VФ,IL are included in Table A3, meanwhile the limiting apparent molar volumes V0Φ ,IL are listed in Table 1. Obviously, the limiting apparent molar volumes increase with the increase of the alkyl chain length of cations. This is due to the fact that the increasing of alkyl chain length could cause the increase of their intrinsic volumes. For a given GBIL (see Fig. 2), the limiting apparent molar volumes in different solvents are in the order: V0Φ , IL(methanol) b V0Φ , IL(propyl alcohol) b V0Φ ,IL(water). GBILs are easier to form hydrogen bonds with water than with alcohol. This is why the limiting apparent molar volumes of GBILs in water are larger than in methanol and propyl alcohol.

ηr ¼ η=η0 ¼ 1 þ Ac1=2 þ Bc þ Dc2

ð4Þ

where η and η0 are the viscosities of the IL solutions and the molecular solvents (water/methanol/propyl alcohol), respectively, c is molarity of the IL, A, B and D are empirical constants. The viscosity A-coefficient reflects the interaction between solutes, while B-coefficient is determined by ion-solvent and solvent-solvent interaction. Eq. (4) can be rearranged as the following  ηr −1 =c1=2 ¼ A þ Bc1=2 þ Dc3=2

ð5Þ

Table 1 The limiting apparent molar volumes V0Φ , IL of GBILs in different kinds of solvents at 298.15 K. [Cnmim][C6H11O7]

n=2 n=4 n=6 n=8 n = 10 n = 12 n = 14

V0Φ ,IL/(cm3 mol−1) H2O

CH3OH

CH3CH2CH2OH

220.41 ± 0.24 249.91 ± 1.16 286.21 ± 0.12 315.17 ± 0.17 354.79 ± 0.73 380.26 ± 0.10 417.79 ± 0.08

201.18 ± 4.03 230.64 ± 0.62 256.19 ± 3.08 282.58 ± 1.12 305.53 ± 1.23 332.82 ± 0.23 362.32 ± 1.70

220.16 ± 4.71 246.74 ± 3.21 275.13 ± 2.22 306.12 ± 0.40 336.60 ± 0.92 372.87 ± 0.10 403.29 ± 2.35

V

n

n Fig. 2. Variation of the limiting apparent molar volumes for the GBILs with the number nCH2 of methylene group (CH2) in the long alkyl chain of cations of [Cnmim][C6H11O7] (n = 2, 4, 6, 8, 10, 12, and 14) in water, methanol, and propyl alcohol at 298.15 K: ■, H2O; ●, CH3OH; ▲, CH3CH2CH2OH.

The B-coefficients were obtained by the fit of experimental data to the equation and are listed in Table 3. It is obvious that these B-coefficients are large and positive. In dipolar aprotic solvents, the structure breaking contribution is negligible due to the positive and

Table 2 \CH2) in different solLimiting apparent molar volumes VΦ,CH20 for the methylene group (\ vents at 298.15 K.a Solvents

H2O

CH3OH

CH3CH2CH2OH

VΦ ,CH20/(cm3 mol−1) Rb

16.45 ± 0.28 0.9991

13.16 ± 0.18 0.9995

15.41 ± 0.30 0.9993

a b

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Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020

Derived by using Eq. (3) in this work. Correlation coefficient.

Table 3 Viscosity A-, B- and D-coefficients of GBILs in various solvents at 298.15 K. [Cnmim][C6H11O7]

A/(dm3/2 mol−1/2)

B/(dm3 mol−1)

D/(dm6 mol−2)

H2O n=2 n=4 n=6 n=8 n = 10 n = 12 n = 14

0.0037 ± 0.0078 0.0236 ± 0.0130 0.0338 ± 0.0031 0.0540 ± 0.0137 0.0716 ± 0.0383 0.1060 ± 0.0340 0.0867 ± 0.0478

0.762 ± 0.043 0.841 ± 0.068 0.923 ± 0.017 1.020 ± 0.076 1.140 ± 0.028 1.203 ± 0.059 1.310 ± 0.089

0.256 ± 0.170 0.978 ± 0.253 1.358 ± 0.074 1.334 ± 0.305 1.651 ± 0.644 -22.180 ± 2.245 181.700 ± 3.735

CH3OH n=2 n=4 n=6 n=8 n = 10 n = 12 n = 14

0.1150 ± 0.0690 0.1030 ± 0.0730 0.1330 ± 0.0160 0.1510 ± 0.0720 0.0840 ± 0.0630 0.0240 ± 0.0072 0.0182 ± 0.0074

0.736 ± 0.032 0.816 ± 0.036 0.854 ± 0.093 0.900 ± 0.035 0.957 ± 0.081 1.013 ± 0.014 1.122 ± 0.156

2.055 ± 0.880 3.065 ± 0.246 3.211 ± 0.409 2.552 ± 1.237 16.690 ± 1.824 76.250 ± 6.436 82.580 ± 8.596

CH3CH2CH2OH n=2 n=4 n=6 n=8 n = 10 n = 12 n = 14

0.0912 ± 0.0470 0.0570 ± 0.0200 0.0125 ± 0.0032 0.1030 ± 0.0009 0.0830 ± 0.0172 0.0640 ± 0.0160 0.1100 ± 0.0054

1.103 ± 0.284 1.169 ± 0.043 1.295 ± 0.021 1.341 ± 0.054 1.452 ± 0.277 1.520 ± 0.028 1.665 ± 0.131

0.987 ± 1.360 3.920 ± 0.880 0.562 ± 0.356 2.377 ± 0.248 5.981 ± 0.194 56.840 ± 1.160 -0.945 ± 0.026

Fig. 3. Variation of the B-coefficients for the GBILs with the number nCH2 of methylene group (CH2) in the long alkyl chain of cations of [Cnmim][C6H11O7] (n = 2, 4, 6, 8, 10, 12, and 14) in water, methanol, and propyl alcohol at 298.15 K: ■, H2O; ●, CH3OH; ▲, CH3CH2CH2OH.

large values of the B-coefficients that come from the tendency of the ions to attract the solvent molecules around themselves [21]. So, these B-coefficients show that structure making effect exits in those systems. It can be found that the B-coefficients of these GBILs increase with the increase of length of alkyl chains in the same solvent (Fig. 3). The increase of intrinsic volumes of solutes will lead the increase of hydrodynamic volumes, which will block their movements. While, for different molecular solvents, B-coefficients are in the order: B(methanol) b B(water) b B(propyl alcohol). It is easy to understand the B-coefficients in propyl alcohol are the largest, because their largest intrinsic volumes lead to the biggest moving resistance. It is believed that the change of the solvent structure, such as the formation of a network of three-dimensional hydrogen bonds, is an important factor influencing B-coefficients [22]. Although the volume of a methanol molecule is larger than that of a water molecule, the ILs can form stronger hydrogen bonds with water than with alcohol. So, the B-coefficients in water are larger than in methanol. A linear relationship also exists between BCH2 and n (the number of methylene groups in the alkyl chain of the cations) B ¼ B½C0 mim½C6 H11 O7  þ BCH2 nCH2

ð6Þ

where BCH2 represents the contribution per methylene group (\\CH2) in the alkyl chains of the cations to the B-coefficients. The BCH2 values are included in Table 4 and show the order: BCH2(methanol) b BCH2(propyl alcohol) b BCH2(water). Hydrophobic groups in water can promote the formation of hydrogen bonds between water molecules, so BCH2 value in water is larger than that in alcohol. The intrinsic volume of propyl alcohol is larger than methanol, so when adding a methylene for GBILs cations, viscosities for GBILs + propyl alcohol systems will have a larger increase. That is why BCH2 in propyl alcohol is larger than in methanol.

Table 4 B-coefficients for the methylene group (\ \CH2) in different solvents at 298.15 K.a Solvents

H2O

CH3OH

CH3CH2CH2OH

BCH2/(dm3 mol−1) Rb

0.046 ± 0.001 0.9979

0.030 ± 0.002 0.9869

0.046 ± 0.002 0.9928

a b

Derived by using Eq. (6) in this work. Correlation coefficient.

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Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020

Table 5 The limiting molar conductivities Λ0 and association constants KA of GBILs in various solvents at 298.15 K. [Cnmim][C6H11O7]

n=2 n=4 n=6 n=8 n = 10 n = 12 n = 14

H2O

CH3OH

CH3CH2CH2OH

Λ0/(S cm2 mol−1)

KA

Λ0/(S cm2 mol−1)

KA

Λ0/(S cm2 mol−1)

KA

62.1 ± 0.1 56.4 ± 0.1 51.8 ± 0.1 49.1 ± 0.1 50.5 ± 0.1 47.3 ± 0.1 43.7 ± 0.1

1.01 ± 0.07 1.56 ± 0.07 1.78 ± 0.11 14.9 ± 0.5 15.3 ± 0.5 16.3 ± 0.7 18.4 ± 0.8

87.8 ± 0.3 80.1 ± 0.2 74.9 ± 0.1 73.0 ± 0.2 70.0 ± 0.2 67.8 ± 0.4 64.5 ± 0.1

42.5 ± 2.0 41.5 ± 2.1 39.3 ± 0.8 38.5 ± 1.7 36.5 ± 1.2 32.5 ± 1.6 29.7 ± 0.3

20.2 ± 0.3 17.6 ± 0.3 16.7 ± 0.3 16.5 ± 0.3 14.4 ± 0.5 13.9 ± 0.2 12.6 ± 0.2

355.2 ± 15.7 226.6 ± 10.6 214.3 ± 10.3 188.4 ± 9.9 185.5 ± 19.8 184.3 ± 9.7 174.2 ± 8.0

3.3. Limiting molar conductivities The values of molar conductivities are obtained from equation and collected in Table A5 Λ ¼ ðκ solution −κ solvent Þ  103 =c

ð7Þ

where κsolution and κsolvent are conductivities of solute and pure solvents, and c is molarity of the ILs in solvents. Two parameters were used to obtain the limiting molar conductivity Λ0 and the ionic association constant for GBILs KA 1 1 cΛK A þ ¼ Λ Λ 0 ðΛ 0 Þ2

Meanwhile, for the same ILs, the order of the limiting molar conductivities in different solvents are: Λ0(methanol) N Λ0(water) N Λ0(propyl alcohol), and the order of association constants are KA(water) b KA(methanol) b KA(propyl alcohol). Λ0 values in the studied solvents increase with decrease of the viscosities of the solvents [23], which implied the motivation of ILs is limited due to the increase of the solvents' viscosities. A linear relationship also exists between Λ0,CH2 and n (the number of methylene groups in the alkyl chain of the cations) Λ 0;CH2 ¼ Λ 0;½C0 mim½C6 H11 O7  þ Λ 0;CH2 nCH2

ð9Þ

ð8Þ

where Λ and c are molar conductivity and molarity of the ILs, respectively. The resulting values are summarized in Table 5. For given solvents, the limiting molar conductivities of different GBILs decreased with the increase of length of alkyl chains (Fig. 4). This trend is similar to that for ILs in some organic solvents [23]. This is mainly because the cations with shorter alkyl chains move more easily. The association constants for different GBILs increased in water, but decreased in alcohol with the increase of length of alkyl chains. From quantum chemistry calculation and electrospray ionization mass spectrometry, it was found that the electrostatic interactions between anions and cations of ILs reduced with the increase of length of alkyl chains [24,25]. It indicates that the association behavior of GBILs in water was affected by hydrophobic interactions rather than electrostatic interaction between anions and cations. In alcohol, the solvation of cations enhanced with the growth of the cationic alkyl chains which resulted from the improvement of van der Waals forces between ILs and alkyl chains of alcohol.

n Fig. 4. Variation of the limiting molar conductivities for the GBILs with the number nCH2 of methylene group (CH2) in the long alkyl chain of cations of [Cnmim][C6H11O7] (n = 2, 4, 6, 8, 10, 12, and 14) in water, methanol, and propyl alcohol at 298.15 K: ■, H2O; ●, CH3OH; ▲, CH3CH2CH2OH.

where Λ0,CH2 represents the contribution per methylene group (\\CH2) in the alkyl chains of the cations to the limiting molar conductivities, and the Λ0 , CH2 values are included in Table 6. Each straight line shows a negative slope, indicating that methylene group has a negative contribution to the values of the limiting molar conductivities of ILs. It is noted that, for different solutions, the order of Λ0 , CH2 is Λ0 , CH2(propyl alcohol) b Λ0,CH2(water) b Λ0,CH2(methanol).

4. Conclusions Seven novel kinds of GBILs were synthesized in this work. The interactions between the ILs and various solvents were studied by measuring their thermodynamic and transport properties including densities, viscosities, and conductivities. Some important parameters involving the limiting apparent molar volumes (V0Φ,IL), B-coefficients and the limiting molar conductivities (Λ0) were all calculated. It is demonstrated that, both V0Φ , IL and B increase with the increase of the alkyl chain length of cations, while Λ0 exhibits opposite tendency. For given GBILs, V0Φ , IL, B, and Λ0 are in the orders: V0Φ , IL(methanol) b V0Φ , IL(propyl alcohol) b V0Φ , IL(water), B(methanol) b B(water) b B(propyl alcohol), and Λ0(methanol) N Λ0(water) N Λ0(propyl alcohol) respectively. Meanwhile, the order of contribution per methylene group to V0Φ ,IL, B, and Λ0 is: VΦ , CH20(methanol) b VΦ , CH20(propyl alcohol) b VΦ , CH20(water), BCH2(methanol) b BCH2(propyl alcohol) b BCH2(water), and Λ0,CH2(propyl alcohol) b Λ0,CH2(water) b Λ0 ,CH2(methanol), respectively. These results indicate that the nature of GBILs and solvents, and the interactions between solvents and solutes all have significant influence on physicochemical properties for the systems. These basic research will provide a new perspective for the study of process chemistry when utilize these GBILs systems.

Table 6 The limiting molar conductivities for the methylene group (\ \CH2) in different solvents.a Solvents

H2O

CH3OH

CH3CH2CH2OH

Λ0 ,CH2/(S cm2 mol−1) Rb

−1.3 ± 0.2 0.9374

−1.8 ± 0.2 0.9665

−0.6 ± 0.1 0.9731

a b

Derived by using Eq. (9) in this work. Correlation coefficient.

Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020

Acknowledgments

Table A3 Densities ρ and apparent molar volumes VΦ,IL for GBILs + solvents at 298.15 K and 1 atm.a

Financial support from the National Natural Science Foundation of China (Nos. 21173070, 21303044, 21573058, 21273061) and the Plan for Scientific Innovation Talent of Henan Province (no. 124200510014) are gratefully acknowledged. Appendix A

Table A1 Purities and sources of the samples used in this work. Chemical

Source

Mass fraction purity

Chlorinated n-butane Chlorinated n-hexane Chlorinated n-octane Chlorinated n-decane Dodecanoic bromide Bromine n-tetradecane Methanol Propanol alcohol Anion exchange resin N-methylimidazole

Alfa Alfa Alfa Alfa Aladdin Aladdin Sinopharm Chemical Sinopharm Chemical Alfa Aladdin Aladdin

N0.99 N0.98 N0.99 N0.99 N0.99 N0.99 N0.993 N0.99

D-Gluconic

acid solution

N0.99 0.49–0.53 aqueous solution

Table A2 The 1H NMR values of gluconate-based ionic liquids. Condition [C2mim][C6H11O7] 400 MHz, D2O

[C4mim][C6H11O7] 400 MHz, CDCl3

[C6mim][C6H11O7] 400 MHz, D2O

[C8mim][C6H11O7] 400 MHz, D2O

[C10mim][C6H11O7] 400 MHz, D2O

[C12mim][C6H11O7] 400 MHz, D2O

[C14mim][C6H11O7] 400 MHz, D2O

1017

Chemical shift δ 8.55 (s, 1H), 7.32 (s, 1H), 7.25 (s, 1H), 4.05 (t, 2H), 3.96–3.97 (d, 1H), 3.86–3.88 (m, 1H), 3.72 (s, 3H), 3.65–3.68 (m, 1H), 3.58–3.63 (m, 2H), 3.49–3.53 (m, 1H), 1.33 (t, 3H). δ 8.55 (s, 1H), 7.31 (s, 1H), 7.26 (s, 1H), 4.03 (t, 2H), 3.96–3.97 (d, 1H), 3.86–3.88 (m, 1H), 3.73 (s, 3H), 3.65–3.68 (m, 1H), 3.58–3.63 (m, 2H), 3.48–3.52 (m, 1H), 1.65–1.72 (m, 2H), 1.11–1.20 (m, 2H), 0.76 (t, 3H). δ 8.55 (s, 1H), 7.31 (s, 1H), 7.26 (s, 1H), 4.03 (t, 2H), 3.96–3.97 (d, 1H), 3.87–3.88 (m, 1H), 3.73 (s, 3H), 3.65–3.69 (d, 1H), 3.60–3.62 (m, 2H), 3.48–3.52 (m, 1H), 1.69–1.72 (m, 2H), 1.12–1.16 (m, 6H), 0.70 (t, 3H). δ 8.60 (s, 1H), 7.36 (s, 1H), 7.32 (s, 1H), 4.08 (t, 2H), 4.02–4.03 (d, 1H), 3.91–3.95 (m,1H), 3.79 (s, 3H), 3.74–3.71 (m, 1H), 3.64–3.68 (m, 2H), 3.54–3.58 (m, 1H), 1.73–1.80 (m, 2H), 1.16–1.20 (m, 10H), 0.75 (t, 3H). δ 8.60 (s, 1H), 7.37 (s, 1H), 7.33 (s, 1H), 4.08 (t, 2H), 4.02–4.03 (d, 1H), 3.91–3.95 (m, 1H), 3.79 (s, 3H), 3.71–3.74 (m, 1H), 3.64–3.68 (m, 2H), 3.54–3.58 (m, 1H), 1.73–1.80 (m, 2H), 1.16 (m, 14H), 0.76 (t, 3H) δ 8.61 (s, 1H), 7.38 (s, 1H), 7.33 (s, 1H), 4.10 (t, 2H), 4.01–4.02 (d, 1H), 3.91–3.95 (m, 1H), 3.80 (s, 3H), 3.71–3.74 (m, 1H), 3.64–3.68 (m, 2H), 3.53–3.58 (m, 1H), 1.71–1.81 (m, 2H), 1.10–1.23 (m, 18H), 0.75 (t, 3H) δ 8.61 (s, 1H) 7.42 (s, 1H), 7.37 (s, 1H), 4.10–4.13 (t, 2H), 4.01–4.02 (d, 1H), 3.93–3.95 (m, 1H), 3.82 (s, 3H), 3.71–3.74 (m, 1H), 3.65–3.69 (m, 2H), 3.54–3.58 (m, 1H), 1.70–1.82 (m, 2H), 1.11–1.25 (m, 22H), 0.75 (t, 3H)

m/(mol kg−1) ρ/(g cm−3) VΦ,IL/ m/(mol kg−1) ρ/(g cm−3) VΦ,IL/ (cm3 mol−1) (cm3 mol−1) H2O [C2mim][C6H11O7] 0 0.977047 0.0379 1.000299 0.0587 1.002058 0.0721 1.003181 0.0908 1.004731 0.1115 1.006424 0.1355 1.008352 [C6mim][C6H11O7] 0 0.977047 0.0390 1.000090 0.0778 1.003062 0.0954 1.004386 0.1149 1.005846 0.1339 1.007262 0.1523 1.008618 [C10mim][C6H11O7] 0 0.977047 0.0199 0.998354 0.0353 0.999358 0.0490 1.000270 0.0772 1.002120 0.0951 1.003300 0.1089 1.004190 [C14mim][C6H11O7] 0 0.977047 0.0571 1.000254 0.0731 1.001117 0.0948 1.002267 0.1135 1.003236 0.1235 1.003742 CH3OH [C2mim][C6H11O7] 0 0.788663 0.0311 0.792210 0.1010 0.800038 0.1582 0.806541 0.2379 0.815320 0.2971 0.821541 [C6mim][C6H11O7] 0 0.788663 0.0652 0.796708 0.0800 0.798467 0.1216 0.803320 0.1391 0.805340 0.1666 0.808420 [C10mim][C6H11O7] 0 0.788663 0.0216 0.791382 0.0231 0.791556 0.0277 0.792108 0.0326 0.792700 0.0380 0.793344 [C14mim][C6H11O7] 0 0.788663 0.0078 0.789856 0.0105 0.790265 0.0112 0.790370 0.0121 0.790503 0.0054 0.789496 CH3CH2CH2OH [C2mim][C6H11O7] 0 0.801548 0.0625 0.807656 0.0845 0.809746 0.1075 0.811959 0.1270 0.813851 0.1661 0.817600 [C6mim][C6H11O7] 0 0.801548

220.08 220.22 220.28 220.38 220.58 220.79

286.10 285.93 285.89 285.82 285.73 285.00

353.40 353.08 352.46 351.88 351.41 351.25

[C4mim][C6H11O7] 0 0.977047 0.0563 1.001795 0.0717 1.003077 0.0827 1.003984 0.0937 1.004890 0.1327 1.008075 [C8mim][C6H11O7] 0 0.977047 0.0437 1.000340 0.0644 1.001880 0.1010 1.004520 0.1301 1.006590 0.1485 1.007870 0.1596 1.008640 [C12mim][C6H11O7] 0 0.977047 0.0666 1.001140 0.0742 1.001580 0.0939 1.002710 0.1174 1.004020 0.1481 1.005690

249.43 249.36 249.34 249.28 249.10

314.75 314.76 314.80 314.83 314.90 314.93

384.45 384.64 385.04 385.43 385.85

418.24 418.35 418.49 418.60 418.71

203.96 204.31 202.18 201.43 202.05

260.99 261.69 263.24 263.57 264.66

327.79 328.14 329.29 329.90 330.67

[C4mim][C6H11O7] 0 0.788663 0.0884 0.799339 0.1023 0.800995 0.1230 0.803442 0.1564 0.807384 0.2780 0.821298 [C8mim][C6H11O7] 0 0.788663 0.0819 0.799318 0.0999 0.801598 0.1232 0.804520 0.1412 0.806764 0.1628 0.809404 0.1724 0.810567 [C12mim][C6H11O7] 0 0.788663 0.0063 0.789577 0.0084 0.789882 0.0124 0.790451 0.0144 0.790739 0.0172 0.791144

227.02 226.92 226.72 226.42 226.12

282.12 282.31 282.45 282.60 282.82 282.95

333.03 333.19 333.46 333.60 333.83

355.39 355.34 355.39 356.11 355.19

228.31 228.82 228.46 227.86 227.23

[C4mim][C6H11O7] 0 0.801548 0.0896 0.811162 0.1200 0.814313 0.1296 0.815301 0.1376 0.816114 0.1578 0.818152 [C8mim][C6H11O7] 0 0.801548

247.28 247.74 247.83 248.00 248.34

(continued on next page)

1018

Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020 Table A4 (continued)

Table A3 (continued) −1

m/(mol kg 0.0302 0.1010 0.1241 0.1497 0.1460

−3

) ρ/(g cm

0.805049 0.812560 0.814950 0.817455 0.817134

[C10mim][C6H11O7] 0 0.801548 0.0218 0.804155 0.0244 0.804460 0.0311 0.805234 0.0350 0.805687 0.0397 0.806224 [C14mim]C6H11O7 0 0.801548 0.0053 0.802171 0.0062 0.802276 0.0074 0.802416 0.0081 0.802497 0.0104 0.802756

−1

m/(mol kg ) VΦ,IL/ (cm3 mol−1) 277.00 280.90 281.73 283.50 282.90

334.90 335.12 335.88 336.33 336.95

−3

) ρ/(g cm

) VΦ,IL/ (cm3 mol−1)

0.0404 0.806190 0.0815 0.810806 0.0767 0.810275 0.0839 0.811075 0.1190 0.814922 0.1599 0.819319 [C12mim][C6H11O7] 0 0.801548 0.0110 0.802841 0.0129 0.803063 0.0170 0.803540 0.0180 0.803655 0.0251 0.804474

306.53 306.79 306.73 306.85 307.11 307.31

373.53 373.65 373.87 373.94 374.34

408.78 409.14 409.64 410.03 410.74

Standard uncertainties u are u(T) = 0.01 K, u(p) = 5 kPa, and u(mIL)% = 0.05%. The combined expanded uncertainty Uc is Uc (d) = 1.0 × 10−5 g cm−3 (0.95 level of confidence).

Table A4 Viscosities η for GBILs + solvents at 298.15 K and 1 atm.a

[C2mim][C6H11O7] 0.0375 0.917 0.0578 0.931 0.0708 0.940 0.0888 0.954 0.1085 0.968 0.1290 0.983 0.1312 0.985 [C4mim][C6H11O7] 0.0554 0.939 0.0703 0.953 0.0808 0.962 0.0913 0.972 0.1085 0.989 0.1281 1.010 [C6mim][C6H11O7] 0.0385 0.930 0.0571 0.949 0.0926 0.986 0.1109 1.010 0.1286 1.030

[C8mim][C6H11O7] 0.0378 0.936 0.0934 1.000 0.1106 1.020 0.1278 1.040 0.1438 1.060

[C10mim][C6H11O7] 0.0198 0.920 0.0348 0.941 0.0480 0.958 0.0749 0.994 0.0918 1.020

[C12mim][C6H11O7] 0.0040 0.900 0.0054 0.903 0.0065 0.904

c/(mol L−1) η/(mPa s) CH3OH

c/(mol L−1) η/(mPa s) CH3CH2CH2OH

0.0079 0.0139

0.906 0.913

0.0098 0.0113

0.556 0.558

0.0103 0.0136

2.032 2.053

[C14mim][C6H11O7] 0.0042 0.903 0.0051 0.906 0.0061 0.909 0.0079 0.917 0.0097 0.924

0.0027 0.0048 0.0082 0.0088 0.0095

0.548 0.550 0.554 0.555 0.556

0.0016 0.0050 0.0059 0.0065 0.0083

1.990 2.008 2.012 2.014 2.022

a

Standard uncertainties u are = 0.01 K, u(p) = kPa, and u(c)% = 0.05%. Theu(T) relative combined ex-5 panded uncertainty Uc % is Uc(η) % = 0.4% (0.95 level of confidence). Table A5 The electric conductivities к and molar conductivities Λ of GBILs at 298.15 K.a

a

c/(mol L−1) η/(mPa s) H2O

c/(mol L−1) η/(mPa s) H2O

c/(mol L−1) η/(mPa s) CH3OH

c/(mol L−1) η/(mPa s) CH3CH2CH2OH

0.0411 0.0784 0.1217 0.1808 0.2237

0.576 0.603 0.636 0.683 0.720

0.0331 0.0667 0.0845 0.0995 0.1292

2.083 2.178 2.187 2.233 2.370

0.0561 0.0686 0.0792 0.0948 0.1198 0.1428

0.588 0.599 0.607 0.620 0.641 0.664

0.0397 0.0489 0.0940 0.1074 0.1226

2.090 2.120 2.291 2.350 2.421

0.0321 0.0508 0.0621 0.0764 0.0936 0.1066 0.1270

0.575 0.589 0.599 0.612 0.626 0.639 0.658

0.0174 0.0474 0.0632 0.0792 0.1161 0.1133

2.048 2.078 2.158 2.280 2.331 2.396

0.0635 0.0771 0.0945 0.1077 0.1234 0.1305

0.603 0.614 0.630 0.641 0.656 0.663

0.0320 0.0603 0.0925 0.1229 0.1070

2.102 2.157 2.323 2.444 2.381

0.0070 0.0105 0.0135 0.0169 0.0181 0.0242

0.551 0.554 0.557 0.560 0.562 0.568

0.0068 0.0098 0.0123 0.0149 0.0174 0.0194 0.0247

2.010 2.019 2.030 2.042 2.050 2.061 2.080

0.0033 0.0050 0.0066

0.548 0.550 0.552

0.0042 0.0064 0.0088

1.999 2.010 2.024

104c/ к/(μS cm−1) Λ/(S cm2 mol−1) 104c/ к/(μS cm−1) Λ/(S cm2 mol−1) (mol L−1) (mol L−1) ([C2mim][C6H11O7] + H2O) 8.18 52.87 60.34 12.17 77.45 59.95 15.39 97.18 59.68 18.19 114.19 59.45 23.14 144.26 59.21 27.94 173.03 58.91 32.15 197.26 58.42 34.38 210.51 58.33 35.50 217.26 58.31 38.92 237.51 58.18 40.03 243.82 58.07

([C2mim][C6H11O7] + CH3OH) 3.01 29.82 87.52 3.80 36.76 86.65 6.46 60.56 86.30 7.92 72.86 85.32 10.27 92.52 84.17 14.01 123.48 82.86 15.80 137.94 82.25 17.97 155.38 81.65 21.34 182.40 80.88 23.20 197.01 80.45 25.01 211.69 79.98

([C2mim][C6H11O7] + CH3CH2CH2OH) 2.34 4.78 19.57 4.03 7.69 18.26 7.87 13.44 16.36 10.17 16.54 15.58 14.93 22.70 14.58 19.27 27.56 13.71 27.91 35.92 12.34 30.61 38.73 12.13 40.76 47.52 11.18 53.09 57.12 10.31 64.00 65.00 9.74 71.19 69.90 9.41 ([C4mim][C6H11O7] + H2O) 4.41 27.19 56.29 6.68 40.18 55.87 8.58 51.06 55.60 9.87 58.38 55.47 11.87 69.73 55.28 13.49 78.81 55.11 15.87 92.14 54.88 18.18 105.02 54.69 20.69 118.94 54.52 23.18 132.66 54.34 28.07 159.44 54.01 31.68 179.10 53.83 ([C4mim][C6H11O7] + CH3CH2CH2OH) 8.69 14.18 15.64 12.32 18.82 14.63 15.39 22.44 13.97 18.26 25.83 13.56 24.32 32.02 12.62 28.69 36.19 12.09 34.20 41.09 11.52 46.64 51.38 10.56 75.91 72.25 9.12 60.44 61.66 9.78 108.76 92.61 8.16

([C4mim][C6H11O7] + CH3OH) 5.95 51.30 78.78 6.39 54.71 78.52 8.10 67.83 77.44 10.02 82.76 76.87 12.41 100.89 76.09 14.42 116.02 75.54 16.22 129.64 75.23 18.17 144.00 74.72 20.19 159.07 74.39 22.12 172.89 73.90 25.10 194.42 73.35 27.47 211.19 72.88

Y. Chen et al. / Journal of Molecular Liquids 223 (2016) 1013–1020

1019

Table A5 (continued) к/(μS cm−1) Λ/(S cm2 mol−1) 104c/ к/(μS cm−1) Λ/(S cm2 mol−1) 104c/ (mol L−1) (mol L−1) 131.12 169.10 203.63

104.67 123.91 139.97

7.65 7.03 6.59

([C6mim][C6H11O7] + H2O) 1.93 11.78 51.94 5.78 32.32 51.43 7.97 43.78 51.07 10.68 57.84 50.74 11.99 64.61 50.60 14.33 76.64 50.42 16.57 88.14 50.26 18.43 97.73 50.15 20.73 109.34 49.98 24.13 126.60 49.80 26.91 140.65 49.65 30.13 156.70 49.46

([C6mim][C6H11O7] + CH3OH) 5.26 42.82 73.39 6.65 53.21 73.12 8.77 68.67 72.32 10.03 77.81 71.94 11.61 89.75 72.03 13.09 100.22 71.53 17.53 131.21 70.39 20.11 149.16 69.92 23.56 172.05 68.98 28.94 207.22 67.83 32.26 228.59 67.19 34.77 244.84 66.83

([C6mim][C6H11O7] + CH3CH2CH2OH) 6.11 10.37 16.26 8.02 12.98 15.50 11.15 16.88 14.51 13.49 19.62 13.94 16.12 22.44 13.34 18.14 24.58 12.98 19.97 26.47 12.70 22.01 28.45 12.39 24.41 30.75 12.07 31.48 37.09 11.29 45.94 48.74 10.17 57.12 56.83 9.537 ([C8mim][C6H11O7] + H2O) 3.88 21.24 48.96 7.24 38.09 48.57 9.74 50.54 48.37 11.74 60.39 48.16 15.75 80.08 47.89 18.11 91.57 47.73 21.27 106.79 47.51 26.84 133.58 47.21 31.92 157.67 46.93 34.23 168.50 46.80 38.39 187.86 46.56

([C8mim][C6H11O7] + CH3OH) 12.87 96.64 69.88 13.35 99.82 69.68 15.07 111.41 69.12 16.71 122.81 68.88 19.63 142.08 68.03 21.40 153.79 67.65 24.30 172.96 67.14 26.00 183.97 66.80 31.70 220.89 65.96

([C8mim][C6H11O7] + CH3CH2CH2OH) 29.30 36.77 12.03 39.38 45.56 11.09 44.90 50.01 10.68 51.01 54.75 10.29 57.58 59.63 9.93 71.63 69.42 9.29 81.67 75.97 8.92 85.43 78.36 8.79 106.78 91.31 8.20 132.24 105.54 7.65 172.39 126.17 7.02 ([C10mim][C6H11O7] + H2O) 11.92 63.14 49.78 14.94 78.30 49.45 17.04 88.77 49.26 18.96 98.29 49.09 21.19 109.36 48.91 24.97 127.94 48.64 31.35 158.91 48.22 34.66 174.95 48.05 38.65 194.11 47.85 42.19 211.02 47.67 44.28 220.86 47.56

([C10mim][C6H11O7] + CH3CH2CH2OH) 6.78 10.03 14.17 21.88 25.58 11.20 36.45 36.54 9.61

([C10mim][C6H11O7] + CH3OH) 2.65 21.65 70.67 4.86 37.13 69.11 6.11 45.80 68.60 8.66 63.58 68.06 10.89 78.77 67.49 12.74 91.38 67.15 14.66 104.10 66.70 18.17 126.85 65.80 21.04 144.95 65.10 23.57 160.89 64.59 28.00 188.16 63.71 31.48 209.41 63.14

Table A5 (continued) к/(μS cm−1) Λ/(S cm2 mol−1) 104c/ к/(μS cm−1) Λ/(S cm2 mol−1) 104c/ (mol L−1) (mol L−1) 70.28 92.01 112.10 139.08 161.33 197.34 226.34

59.17 71.54 82.10 95.21 105.31 120.54 132.06

8.07 7.45 7.02 6.56 6.26 5.86 5.59

([C12mim][C6H11O7] + H2O) 4.94 25.45 47.08 7.44 37.43 46.69 11.51 56.86 46.38 14.81 72.43 46.10 16.96 82.46 45.94 20.21 97.54 45.70 23.49 112.67 45.50 26.45 126.21 45.32 29.65 140.83 45.15 33.24 157.22 45.00 37.27 175.33 44.79

([C12mim][C6H11O7] + CH3OH) 1.42 13.33 75.51 3.34 26.53 70.00 5.08 38.30 68.33 6.16 45.83 67.97 7.66 55.65 66.98 9.20 65.74 66.29 10.34 73.20 65.93 12.21 85.15 65.21 13.99 96.68 64.80 16.28 110.98 64.10 25.89 169.26 61.91

([C12mim][C6H11O7] + CH3CH2CH2OH) 23.98 26.63 10.64 29.06 30.83 10.17 32.85 33.77 9.85 37.79 37.47 9.50 43.89 41.80 9.13 55.67 48.92 8.42 71.97 58.78 7.83 81.18 63.83 7.54 103.51 75.55 6.70 127.05 86.92 6.56 151.02 97.65 6.20 184.12 111.44 5.80 213.00 122.69 5.52 ([C14mim][C6H11O7] + H2O) 6.17 30.00 44.93 8.65 41.57 44.85 12.49 59.02 44.48 14.61 68.45 44.20 18.53 85.76 43.82 21.10 97.02 43.59 24.00 109.65 43.36 26.87 122.06 43.16 31.13 140.27 42.87 34.66 155.18 42.63 40.28 178.69 42.28

([C14mim][C6H11O7] + CH3OH) 0.77 7.80 67.35 1.11 10.12 66.98 1.65 13.86 66.63 2.24 17.89 66.45 3.71 27.25 64.19 4.68 33.67 64.06 5.50 39.02 63.92 7.20 50.03 63.47 8.25 56.77 63.19 11.43 76.65 62.30 13.31 88.28 61.85

([C14mim][C6H11O7] + CH3CH2CH2OH) 38.12 35.00 8.80 46.17 40.10 8.33 58.04 47.08 7.78 72.50 54.89 7.26 81.37 59.41 7.00 97.64 67.23 6.60 108.78 72.31 6.37 132.52 82.50 5.97 191.74 105.21 5.26 216.58 113.88 5.04 248.20 124.36 4.80 a The (relative) standard uncertainties u are u(T) = 0.01 K u(p) = 5 kPa, u(mS)% = 0.05%, u(к) = 0.5%, and u(Λ) = 0.5%.

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