Prediction of the thermodynamic properties of 1-alkyl-3-methylimidazolium lactate ionic liquids [C n mim][Lact] (n = 2, 3, 4, 5, and 6) by parachor

Abstract

An ionic liquid (IL) based on lactate, 1-butyl-3-methylimidazolium lactate ([C4mim][Lact]), has been prepared and characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Since the IL can form strong hydrogen bonds with water, trace water is a problematic impurity in the IL. Using the standard addition method (SAM), the density, refractive index and surface tension of [C4mim][Lact] were measured in the temperature range (308.15 to 343.15 ± 0.05) K. On the basis of the experimental data, the parachor and molar volume for [C4mim][Lact], and the molecular volume V m, surface tension γ, molar enthalpy of vaporization Δl g H m 0, refractive index n D, and the thermal expansion coefficients α, for the homologues [C n mim][Lact] (n = 2, 3, 4, 5, and 6) were estimated using semi-empirical methods. The estimated values are in good agreement with the experimental data.