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Amino acid ionic liquids (AAILs) [C(5)mim][Gly] (1-pentyl-3-methylimidazolium glycine) and [C(6)mim][Gly] (1-hexyl-3-methylimidazolium glycine) were prepared by the neutralization method and characterized by (1)H NMR spectroscopy and differential scanning calorimetry (DSC). The values of their density, surface tension, and refractive index were measured in the temperature range of 293.15-343.15 (±0.05) K. Since the AAILs can strongly form hydrogen bonds with water, the small amounts of water are difficult to remove from the AAILs by common methods. In order to eliminate the effect of the impurity water, the standard addition method (SAM) was applied to these measurements. In terms of semiempirical method, physicochemical properties molecular volume V(m), standard molar entropy S(0), parachor P, surface tension γ, thermal expansion coefficients α, molar refraction R(m), and refractive index n(D) of the homologue of [C(n)mim][Gly] (n = 2-6) were predicted. In comparison with the values of [C(2)mim][Gly] in literature, the predicted results were in good agreement within an order of magnitude.

According to Fukumoto's method, a new series of ionic liquids (ILs) based on alanine, [Cnmim][Ala] ( n=2,3,4,5,6), which comprise 1-alkyl-3-methylimidazolium cation ([Cnmim](+)) and alanine anions ([Ala] (-)), were prepared and characterized. In terms of standard addition method, the density and surface tension of amino acid ILs [Cnmim][Ala] (1-alkyl-3-methylimidazolium alpha-aminopropionic acid salt) were measured in the temperature range 293.15-343.15+/-0.05 K. The volume and surface properties of the ILs [Cnmim][Ala] were discussed. A new method of determining parachor of ionic compound was proposed and was applied to estimate the physicochemical properties of amino acid ionic liquids (AAILs): molecular volume, surface tension, molar enthalpy of vaporization, and thermal expansion coefficient. In comparison with Deetlefs's method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.

Three novel ether-functionalized ionic liquids (ILs) 1-ethyl-3-(2-methoxyethyl)-imidazolium acetate, [C 2 2O1IM][OAc], 1-ethyl-3-(2-methoxyethyl)-imidazolium thiocyanate, [C 2 2O1IM][SCN], 1-ethyl-3-(2-methoxyethyl)-imidazolium trifluoromethanesulfonate, [C 2 2O1IM][TfO], and two ILs 1-ethyl-3-(2-methoxyethyl)-imidazolium dicyanamide, [C 2 2O1IM][DCA], 1-ethyl-3-(2-methoxyethyl)-imidazolium bis(trifluoromethylsulfonyl)imide, [C 2 2O1IM][NTF 2 ] were prepared and characterized. Their density and surface tension were measured at T = (298.15–338.15) K. As a new theoretical model, the ionic molar surface Gibbs free energy, g i , was put forward. The ionic molar surface Gibbs free energy, g − , for [BF 4 ] − , which was as reference ion, was obtained in terms of the extrathermodynamic assumptions so that the ionic molar surface Gibbs free energy, g + , of the corresponding cations, [C n mim] + (n = 2–6), were determined. In terms of the g + values of [C n mim] + (n = 2–6), the g − values of 12 kinds of anions were determined and then the average g + value of [C 2 2O1IM] + (9.52 ± 0.21 kJ·mol −1 ) was gotten. By using the values of these g i , the predicted values of molar surface Gibbs free energy, g est , and surface tension, γ est , for [C 2 2O1IM][X] (X = OAC, SCN, DCA, TfO, NTF 2 ) and other 45 ionic liquids were estimated. In comparison, the predicted values correlated quite well with their matching experimental values. [ABSTRACT FROM AUTHOR]

Highlights: [•] for [C6mim][OAc] were obtained in the temperature range of (288.15 to 308.15±0.01) K. [•] The , (ΔH + +ΔH −), ΔH + ([C6mim]+) for [C6mim][OAc] solution were calculated. [•] The apparent relative molar heat capacity, Φ C p , were also calculated for [C6mim][OAc]. [ABSTRACT FROM AUTHOR]

Three propionic acid ionic liquids(PrAILs), 1-alkyl-3-methylimidazoliumpropionate ([Cnmim][Pro] (n= 4, 5, 6)), were prepared by the neutralization method and characterizedby 1H NMR spectroscopy. The values of the densities andsurface tensions of aqueous [C4mim][Pro], [C5mim][Pro], and [C6mim][Pro] with various molalities weredetermined at 298 K, and the values of the parachor for these solutionswere calculated. The values of the apparent molar volumes and partialmolar volumes at infinite dilution for the ILs were estimated in termsof Pitzer’s theory. With the use of Li’s model of surfacetension and the empirical equation of the parachor, the values ofthe surface tensions of these aqueous solutions for three PrAILs wereestimated and the estimated values were in good agreement with experimentalones. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two ILs [C2mim][Lact] and [C5mim][Lact] were prepared. [•] The density, surface tension and refractive index for two ILs were measured in terms of SAT. [•] Using Kabo’s and Rebelo’s method, the molar enthalpy of evaporation for two ILs was estimated. [•] The surface tension was estimated using the parachor and the refractive index. [ABSTRACT FROM AUTHOR]

Highlights: [•] for [C3mim][OAc] were obtained in the temperature range of (288.15 to 308.15±0.01)K. [•] The hydration enthalpy of cation and anion in infinite dilution aqueous was obtained at 298.15K. [•] The and for [C3mim][OAc] were also calculated. [ABSTRACT FROM AUTHOR]

Abstract: A new amino acid ionic liquid (AAIL) [C3mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C3mim][Val] with known amounts of water and with different concentrations in molality were measured at T= 298.15K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C3mim][Val] without water, =(−55.7±0.4)kJ·mol−1, was obtained. The hydration enthalpy of the cation [C3mim]+, ΔH + ([C3mim]+)=−226kJ·mol−1, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, ΔD H m(m i → m f), of aqueous [C3mim][Val] with various values of molality were measured. The values of ΔD H m(m i → m f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, φL, calculated using Pitzer’s ion-interaction model. [Copyright &y& Elsevier]

Air and water stable ionic liquids (ILs) based on catalyticfunctionalmetal rhenium, [Cnmim][ReO4](n= 2,4,5,6)(1-alkyl-3-methylimidazolium perrhenate),are designed and synthesized. Their density and surface tension aremeasured in the temperature range of 293.15–343.15 ± 0.05K. Some physical-chemical properties of the ILs have been calculatedor estimated by the empirical methods. The ion parachor is put forwardand calculated by two extrathermodynamic assumptions. According tothe interstice model, the thermal expansion coefficient of ILs [Cnmim][ReO4], α, are calculatedand in comparison with experimental values, their magnitude orderis in good agreement. [ABSTRACT FROM AUTHOR]