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A series of 1-(2-alkoxyethyl)-3-methylimidazolium + [anion] ionic liquids including 1-(2-methoxyethyl) -3-methylimidazolium chloride, 1-(2-methoxyethyl) -3-methylimidazolium dl-threonine, and 1-(2-...

Amino acid ionic liquids [Cnmim][Ala] (n = 3, 4, 5) (1-alkyl-3-methylimidazolium alanine salt) were prepared by the neutralization method. The density and viscosity for aqueous solutions of the ionic liquids (ILs) with various molalities were measured at T = (288.15 to 328.15) K with an interval of 5 K. In terms of the Jones–Dole equation, the viscosity B-coefficients with large positive values and dB/dT < 0 were obtained, and these facts implied that the ionic liquids are water-structure-making. According to Feakins, the contribution of the solute per mole to the free energy of activation for viscous flow of the solution, Δμ2⧧0, or called as the standard molar activation free energy, was obtained at different temperatures. Under the constant molality of solution, ΔH2⧧0 (the activation enthalpy of the activation for viscous flow of aqueous [Cnmim][Ala] (n = 3, 4, 5)) is a temperature-independent constant. This implies that the activation process of the solute for viscous flow of aqueous [Cnmim][Ala] (n = ...

Glycine ionic liquids [C3mim][Gly] (1-propyl-3-methylimidazolium glycine) and [C4mim][Gly] (1-butyl-3-methylimidazolium glycine) have been prepared by the neutralization method and characterized by 1H NMR spectroscopy and DSC trace. The values of density and surface tension of aqueous [C3mim][Gly] and [C4mim][Gly] with various molality were determined in the temperature range of (288.15 to 328.15 ± 0.05) K, and the experimental values of parachor for these solutions were calculated. Using the empirical equation of parachor, the surface tension of these aqueous solutions was estimated, and the estimated values are in good agreement with experimental values within error.

The density and surface tension of the ionic liquid (IL) [C2mim][B(CN)4] (1-ethyl-3-methylimidazolium tetracyanoborate) were measured in a temperature range from (283.15 to 338.15) K. In terms of Glasser’s semiempirical relation of ILs, the standard molar entropy and the lattice energy of the homologous series of ILs [Cnmim][B(CN)4] were estimated, respectively. Using Kabo’s method and Rebelo’s method, the molar enthalpy of vaporization of [C2mim][B(CN)4], ΔlgHm0 (298 K), at 298 K, and ΔlgHm0 (Tb), at hypothetical normal boiling point, Tb = 680 K, was estimated, respectively. According to the interstice model, the thermal expansion coefficient of [C2mim][B(CN)4], α = 4.77·10−4 K−1, was estimated and was in good agreement with experimental value.

An amino acid ionic liquid (AAIL) [C3mim][Glu] (1-propyl-3-methylimidazolium glutamate) was prepared by the neutralization method and characterized by 1H NMR spectroscopy and DSC trace. Since the AAIL has a strong hydrogen bonding ability, the water content (8.41 ± 0.01)·10−3 mass fraction in the IL is difficult to remove by a common method, so trace water becomes the most problematic impurity. To eliminate the effect of the impurity water, the standard addition method (SAM) was applied to the measurement of densities and surface tensions for [C3mim][Glu] in the temperature range of (318.15 to 343.15 ± 0.05) K and (318.15 to 338.15 ± 0.05) K, respectively. Since per methylene (−CH2−) group in the alkyl chains of the imidazolium-based ionic liquids has almost the same chemical environment, using semiempirical methods we may predict physicochemical properties of 1-alkyl-3-methylimidazolium glutamate [Cnmim][Glu] (n = 1, 2, 3, 4, 5, 6): the molecular volume, Vm, the standard molar entropy, S0, the parachor, ...

The density and surface tension of the air- and water-stable hydrophobic ionic liquid (IL) 1-ethyl-3-methylimizazolium tris(pentafluoroethyl) trifluorophosphate (CAS Registry No.: 377739-43-0; [C2mim][PF3(CF2CF3)3]) were measured in the range of T = (283.15 to 338.15) K. The other physicochemical properties of the IL [C2mim][PF3(CF2CF3)3] at 298.15 K were estimated in terms of empirical and semiempirical equations, as well as the interstice model theory. These properties include molecular volume, standard molar entropy, lattice energy, the parachor, molar enthalpy of vaporization, interstice volume, thermal expansion coefficient, interstice fraction, and so forth. Then, the physicochemical properties of the ILs [Cnmim][PF3(CF2CF3)3] (n = 1, 3, 4, 5, 6) family were predicted in terms of the estimated values of molecular volume and the parachor.

A new amino acid ionic liquid, [C3mim][Glu] (1-methyl-3-propylimidazolium glutamic acid salt), was prepared by a neutralization method and characterized by 1H NMR and TA. Using an Anton Paar model DMA 4500 oscillating U-tube densitometer, the densities of aqueous [C3mim][Glu] were measured over mole fraction of IL from 0.039 to 0.543 in the temperature range of T = (283.15 to 338.15) K at intervals of 5 K. Values of the apparent molar volumes of aqueous [C3mim][Glu] were calculated and were treated by Pitzer−Simonson (PS) equation, Pitzer−Simonson−Clegg (PSC) equation, and the simplified PSC equation. In comparison with the values of PS and the simplified PSC parameters, the PSC parameters have a smaller standard deviation. Obviously, when the number of parameters augments, the fitting accuracy increases.

The ionic liquid (IL) [C6mim][InCl4] (1-methyl-3-hexylimidazolium chloroindium) was prepared by directly mixing InCl3 and 1-methyl-3-hexylimidazolium chloride with a molar ratio of 1:1 under dry argon. The density and surface tension of the IL were determined in the temperature range of (283.15 to 338.15) K. The ionic volume and surface entropy of the IL were estimated by extrapolation, respectively. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated, respectively. Using Kabo's method and Rebelo's method, the molar enthalpy of vaporization of the IL, ΔlgHm0 (298 K), and ΔlgHm0 (Tb) at a hypothetical normal boiling point, Tb = 787 K, were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL [C6mim][InCl4] was estimated.

An ionic liquid (IL), [C4Py][Al2Cl7] (n-butylpyridinium heptachlorodialuminate), was prepared, and its density and surface tension were measured under dry argon in the temperature range from (298.15 to 333.15) K. The experimental data showed that the Eotvos equation was applicable to the IL and the experimental parachor value was larger than that calculated from neutral parachor contribution which did not consider the Coulomb interaction in IL. In terms of Glasser's theory, the molar entropy, S0, and the lattice energy, UPOT, were estimated. Using Kabo's method the molar enthalpy of vaporization ΔlgHm0 (298 K) and using the interstice model the thermal expansion coefficient, α, for [C4Py][Al2Cl7] were predicted, respectively.

Molar heat capacities (Cp,m) of the room-temperature ionic liquid (IL) 1-propyl-3-methylimidazolium glutamic acid salt ([C3mim][Glu]) were measured with a high-precision automated adiabatic calorimeter (AC) in the temperature range of T = (85 to 360) K. A glass transition was observed at 239.861 K. The enthalpy and entropy of the glass transition were determined to be 2.87 kJ·mol−1 and 11.97 J·K−1·mol−1, respectively. Two polynomial equations of molar heat capacity as a function of the temperature were fitted before and after the glass transition. The thermodynamic functions (HT − H298.15) and (ST − S298.15) were derived from the molar heat capacity data in the temperature range of T = (85 to 360) K with an interval of 5 K.

A new novel amino acid ionic liquid [C4mim][Gly] (1-butyl-3-methylimidazolium glicine) was prepared by the neutralization method. The molar enthalpies of solution, ΔsolHm(wc), of [C4mim][Gly] with various amounts of water and with various molalities were measured by the solution−reaction isoperibol calorimeter at (298.15 ± 0.01) K. According to Archer’s method, the standard molar enthalpies of solution of [C4mim][Gly] with known amounts of water, ΔsolH0m(wc), were obtained. To eliminate the effect of the small amount of water in [C4mim][Gly], a linear fitting of ΔsolH0m(wc) against water content was carried out so that a good straight line was obtained, and the intercept was the standard molar enthalpy of solution of [C4mim][Gly] without water, ΔsolH0m = (−46.02 ± 0.19) kJ·mol−1. Using Glasser’s lattice energy theory, the hydration enthalpy of the glycine anion [Gly]− was estimated.