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

Abstract

A new ionic liquid [C3mim][Val] (1-propyl-3-methylimidazolium valine) was synthesized and characterized by 1H 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 [C3mim][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 [C3mim][Val], a series of physicochemical properties—the molecular volume (Vm), surface tension (γ), refractive index (nD), molar enthalpy of vaporization (ΔlgHm0), the thermal expansion coefficient (α) values, the standard molar entropy (S0), and the molar polarization (Rm)—for the homologue of [Cnmim][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 [C2mim][Val].