Jia-Zhen Yang

A new theory for ionic liquids—the Interstice Model

This paper reports measurements of the surface tension of ionic liquid EMISE (1-ethyl-3-methylimidazolium ethyl sulfate) using the forced bubble method at 278.15 to 323.15 K and densities of EMISE using a Westphal balance at 278.15 to 338.15 K. At the same time, a new theoretical model, the interstice model, is put forward. Applying the model, an expression of the average volume of the interstices, v, was obtained. The calculated volume fraction of the total interstices is 0.12 for ionic liquid EMISE and is in good agreement with that of the majority of materials which exhibit a 10∼15% volume expansion in transition from the solid to liquid state. The value of the thermal expansion coefficient calculated from the model is 5.24 × 10−4 K−1 and is in good agreement with the experimental value 5.37 × 10−4 K−1 at 298.15 K.

Study on Physicochemical Properties of Ionic Liquids Based on Alanine [Cnmim][Ala] (n = 2,3,4,5,6)

According to Fukumotos 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 Deetlefss method of using neutral parachor contribution, the method proposed in this work makes smaller error in estimating properties of AAILs.

Studies on room temperature ionic liquid InCl3–EMIC

Abstract A new room temperature ionic liquid (RTIL) has been prepared by directly mixing InCl3 and 1-ethyl-3-methylimidazolium chloride (EMIC) under dry nitrogen atmosphere. The phase diagram of the binary system InCl3–EMIC was determined by DSC. Both Raman scattering and ab inito calculations indicate that InCl4− is the predominant indium-containing species in the ionic liquid. And it was further confirmed by NMR experiments.

Estimation of physicochemical properties of ionic liquids 1-alkyl-3-methylimidazolium chloroaluminate.

The density and surface tension of ionic liquids [C(2)mim][AlCl(4)] (1-ethlyl-3-methyl imidazolium chloroaluminate) and [C(6)mim][AlCl(4)] (1-hexyl-3-methylimidazolium chloroaluminate) were measured in the temperature range from 283.15 to 338.15 +/- 0.05 K. In terms of these experimental results, the estimation of physicochemical properties of 1-alkyl-3-methylimidazolium chloroaluminate ([C(n)mim][AlCl(4)], n = 1-6) was carried out. With the use of the parachor, the values of surface tension of the ILs were predicted. In terms of Glassers theory, the standard molar entropy, lattice energy, and surface properties of the ILs were estimated. With the use of Kabos method and Rebelos method, the molar enthalpy of vaporization of the ILs, Delta(l)(g)H(m)(0), was predicted. According to the interstice model, the values of the thermal expansion coefficient of the ILs were also estimated. Since the magnitude order of the thermal expansion coefficient estimated by the model is in good agreement with that measured experimentally, this result means that the interstice model is reasonable.

Estimation of physicochemical properties of ionic liquid C6MIGaCl4 using surface tension and density

An ionic liquid (IL) C6MIGaCl4 (1-methyl-3-hexylimidazolium chlorogallate) was prepared by directly mixing GaCl3 and 1-methyl-3-hexylimidazolium chloride with molar ratio of 1/1 under dry argon. The density and surface tension of the IL were determined in the temperature range of 283.15-338.15 K. The ionic volume and surface entropy of the IL were estimated by extrapolation, respectively. In terms of Glassers theory, the standard molar entropy and lattice energy of the IL were estimated, respectively. By use of Kabos method, the molar enthalpy of vaporization of the IL, Delta lgHm0 (298 K), at 298 K was estimated. According to the interstice model, the thermal expansion coefficient of IL C6MIGaCl4, alpha, was calculated and in comparison with experimental value; their magnitude order is in good agreement.

Ionic Parachor and Its Application in Acetic Acid Ionic Liquid Homologue 1-Alkyl-3-methylimidazolium Acetate {[Cnmim][OAc](n = 2,3,4,5,6)}

Five acetic acid ionic liquids (AcAILs) [C(n)mim][OAc](n = 2,3,4,5,6) (1-alkyl-3-methylimidazolium acetate) were prepared by the neutralization method and characterized by (1)HNMR spectroscopy and differential scanning calorimetry (DSC). The values of their density and surface tension were measured at 298.15 ± 0.05 K. Since the AcAILs can strongly form hydrogen bonds with water, the small amounts of water are difficult to remove from the AcAILs by common methods. In order to eliminate the effect of the trace water, the standard addition method (SAM) was applied to these measurements. As a new concept, ionic parachor was put forward. [OAc](-) was seen as a reference ion, and its individual value of ionic parachor was determined in terms of two extrathermodynamic assumptions. Then, the values of ionic parachors of a number of anions, [NTf(2)](-), [Ala](-), [AlCl(4)](-), and [GaCl(4)](-), were obtained by using the value of the ionic parachor of the reference ion; the parachor and surface tension of the investigated ionic liquids in literature were estimated. In comparison, the estimated values correlate quite well with their matching experimental values.

Predicting Properties of Amino Acid Ionic Liquid Homologue of 1-Alkyl-3-methylimidazolium Glycine

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.

Determination of the Enthalpy of Vaporization and Prediction of Surface Tension for Ionic Liquid 1-Alkyl-3-methylimidazolium Propionate [Cnmim][Pro](n = 4, 5, 6)

With the use of isothermogravimetrical analysis, the enthalpies of vaporization, Δ(g)lH(o)m(T(av)), at the average temperature, T(av) = 445.65 K, for the ionic liquids (ILs) 1-alkyl-3-methylimidazolium propionate [C(n)mim][Pro](n = 4, 5, 6) were determined. Using Verevkins method, the difference of heat capacities between the vapor phase and the liquid phase, Δ(g)lC(p)(o)m, for [C(n)mim][Pro](n = 2, 3, 4, 5, 6), were calculated based on the statistical thermodynamics. Therefore, with the use of Δ(g)lC(p)(o)m, the values of Δ(g)lH(o)m(T(av)) were transformed into Δ(g)lH(o)m(298), 126.8, 130.3, and 136.5 for [C(n)mim][Pro](n = 4, 5, 6), respectively. In terms of the new scale of polarity for ILs, the order of the polarity of [C(n)mim][Pro](n = 2, 3, 4, 5, 6) was predicted, that is, the polarity decreases with increasing methylene. A new model of the relationship between the surface tension and the enthalpy of vaporization for aprotic ILs was put forward and used to predict the surface tension for [C(n)mim][Pro](n = 2, 3, 4, 5, 6) and others. The predicted surface tension for the ILs is in good agreement with the experimental one.

Ionic Parachor and Its Application II. Ionic Liquid Homologues of 1‑Alkyl-3-methylimidazolium Propionate {[Cnmim][Pro] (n = 2−6)}

Five propionic acid ionic liquids (PrAILs) [C(n)mim][Pro] (n = 2-6) (1-alkyl-3-methylimidazolium propionate) have been prepared by the neutralization method and characterized by (1)H NMR spectroscopy and differential scanning calorimetry (DSC). Their density, ρ, surface tension, γ, and refractive index, n(D), were measured at (298.15 ± 0.05) K, and the experimental values of parachor for the PrAILs were calculated. Using the parachor values of [C(n)mim](+) obtained by Guan et al., the anionic parachor values of [C(n)mim][Pro] (n = 2-6), [C(2)mim][RBF(3)] (R = N-C(n)H(2n+1) (n = 1-5)), [C(n)mim][Gly] (n = 2-6), and [C(n)mim][PF(3)(CF(2)CF(3))(3)] (n = 1-6) were determined. Then, the parachor, surface tension, and refractive index of the ILs investigated in this work were estimated. The estimated values correlate quite well with the corresponding experimental values.

Physicochemical properties of air and water stable rhenium ionic liquids.

Air and water stable ionic liquids (ILs) based on catalytic functional metal rhenium, [C(n)mim][ReO(4)](n = 2,4,5,6)(1-alkyl-3-methylimidazolium perrhenate), are designed and synthesized. Their density and surface tension are measured in the temperature range of 293.15-343.15 ± 0.05 K. Some physical-chemical properties of the ILs have been calculated or estimated by the empirical methods. The ion parachor is put forward and calculated by two extrathermodynamic assumptions. According to the interstice model, the thermal expansion coefficient of ILs [C(n)mim][ReO(4)], α, are calculated and in comparison with experimental values, their magnitude order is in good agreement.