Reactivity of anionic nucleophiles in ionic liquids and molecular solvents

The nucleophilic reactivity of a representative series of anions has been measured in non nucleophilic imidazolium ionic liquids (IL) in the reaction with n-alkyl methanesulfonates and compared with that found in common molecular solvents ( MeOH, DMSO, PhCl). The reactivity depends on both the imidazolium cation-anion interaction and the specific solvation by water present in the IL, the water playing the main effect, in particular with hydrophilic anions. Removal of the largest quantity of water remarkably increases the ion pair reactivity in the IL up to rate constant value k comparable with those obtained in DMSO and in low polarity media such as PhCl.