Liquid–Liquid Equilibrium of Cholinium-Derived Bistriflimide Ionic Liquids with Water and Octanol

Abstract

The liquid–liquid equilibria of mixtures of cholinum-based ionic liquids (<i>N</i>-alkyl-<i>N,N</i>-dimethylhydroxyethylammonium bis­(trifluoromethane)­sulfonylimide, [N_{11<i>n</i>2OH}]­[Ntf₂], <i>n</i> = 1, 2, 3, 4, and 5) plus water or 1-octanol were investigated at atmospheric pressure over the entire composition range. The experiments were conducted between 265 and 385 K using the cloud-point method. The systems exhibit phase diagrams consistent with the existence of upper critical solution temperatures. The solubility of [N_{1 1 <i>n</i> 2OH}]­[Ntf₂] in water is lower for cations with longer alkyl side chains (larger <i>n</i> values). The corresponding trend in the octanol mixtures is reversed. The ([N_1 1 1 2OH]­[Ntf₂] + water + octanol) ternary system shows triple liquid–liquid immiscibility at room temperature and atmospheric pressure. A combined analytic/synthetic method was used to estimate the corresponding phase diagram under those conditions. Auxiliary molecular dynamics simulation data were used to interpret the experimental results at a molecular level