Prediction of Physicochemical Properties of Valine Ionic Liquids [Cnmim][Val] (n = 2, 3, 4, 5, 6) by Empirical Methods: 2

A new ionic liquid [C 3 mim] [Val] (1-propyl-3-methylimidazolium valine) was synthesized and characterized by 1 H NMR. To avoid the influence of trace water in the ionic liquid (IL), the standard addition method (SAM) was employed; the density and surface tension of the [C 3 mim] [Val] were determined over the temperature range of 303.15―333.15 K (±0.05 K). The experimental density, surface tension, and parachor values at 298.15 K are in good agreement with that predicted by Tong et al. [J. Tong et al., Ind. Eng. Chem. Res. 2011, 50, 2418-2423]. Based on the experimental data for [C 3 mim][Val], a series of physicochemical properties—the molecular volume (V m ), surface tension (y), refractive index (n D ), molar enthalpy of vaporization (Δ l g H m 0 ), the thermal expansion coefficient (α) values, the standard molar entropy (S 0 ), and the molar polarization (R m )―for the homologue of [C n mim] [Val] (n = 2, 4, 5, 6) were estimated using the empirical methods. The estimated results are consistent with one of Tong's estimations, in terms of the experimental data for [C 2 mim] [Val].