Isotope effects on miscibility of 1-alkyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imides with aromatic hydrocarbons

The liquid–liquid miscibility temperatures as a function of composition and deuterium substitution have been experimentally determined for the binary mixtures of 1-decyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide, [C10MIM][NTf2], and 1-dodecyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide, [C12MIM][NTf2] with benzene and toluene and their deuterated forms. All systems exhibit upper critical solution temperatures (UCSTs) and better miscibility for ionic liquids with longer alkyl chain. The interchange of benzene for toluene results in worse miscibility for [C10MIM][NTf2] and better for [C12MIM][NTf2]. Deuteration of the aromatics leads to better miscibility in each case. The sign of the isotope effect is in agreement with expectations and its value seems to be seriously affected by the neighborhood of the hypercritical state.