Polarity Prediction of New Ether-Functionalized Ionic Liquids─[COC₄mim][Cl] and [COC₄mim][Asp]

Abstract

Ether-functionalized ionic liquids (ILs) 1-(4-methoxybutyl)-3-methylimidazolium chloride ([COC4mim]­[Cl]) and 1-(4-methoxybutyl)-3-methylimidazolium aspartic acid ([COC4mim]­[Asp]) were successfully prepared. In terms of the standard addition method, the experimental values of the surface tension, density, and refractive index of these ether-functionalized ILs were obtained at 288.15–318.15 K. Using the Lorentz–Lorenz empirical equation, the values of the molar refraction and molar polarizability for [COC4mim]­[Cl] and [COC4mim]­[Asp] ILs were calculated. According to the definition of the polarity coefficient, the polarity of samples and other ILs was estimated. For the same anion, the polarity of the same series of ILs gradually reduced with increasing carbon chain length of ILs. For the same cation, the polarity of ILs was also influenced by anionic species. The prediction result of the polarity coefficient was in good agreement with δμ.