Prediction of the Physicochemical Properties of Valine Ionic Liquids [C_<i>n</i>mim][Val] (<i>n</i> = 2,3,4,5,6) by Semiempirical Methods

Abstract

An amino acid ionic liquid (AAIL), [C 2 mim][Val] (1-ethyl-3-methy-limidazolium valine), was synthesized and characterized by 1 H NMR. To avoid the influence of trace water in the IL, in terms of the standard addition method (SAM), the density, surface tension, and refractive index for [C 2 mim][Val] were measured in different temperature ranges. On the basis of parachor and molar volume for [C 2 mim][Val], the molecular volume, V m, surface tension, γ, molar enthalpy of vaporization, Δ l g H m °, refractive index, n D, the thermal expansion coefficients, α, the standard molar entropy, S °, and the molar polarization, R m, for the homologue of [C n mim][Val] ( n = 2, 3, 4, 5, 6) were estimated using semiempirical methods. The estimated results were consistent with the experimental data in the order of magnitude.