A Simple and Practical Method for the Preparation and Purity Determination of Halide‐Free Imidazolium Ionic Liquids

Abstract

Abstract The reaction of N ‐alkylimidazole with alkyl sulfonates at room temperature affords 1,3‐dialkylimidazolium alkanesulfonates as crystalline solids in high yields. The alkanesulfonate anions can be easily substituted by a series of other anions [BF 4 , PF 6 , PF 3 (CF 2 CF 3 ) 3 , CF 3 SO 3 and N(CF 3 SO 2 ) 2 ] by simple reaction of anions, salts, or acids in water at room temperature. Extraction with dichloromethane, filtration through a short basic alumina column and solvent evaporation affords the desired ionic liquids in 80–95% yield. The purity (>99.4%) of these ionic liquids can be determined by 1 H NMR spectra using the intensity of the 13 C satellites of the imidazolium N ‐methyl group as internal standard.