Three new protic ionic liquids based on 2-methylpyridinium were prepared and characterized. Their catalytic activities for the tert-butylation of phenol and the esterification of cyclic olefins with acetic acid were examined and satisfactory results were obtained over 2-methylpyridinium trifluoromethanesulfonate ([2-MPyH]OTf). Hammett method was used to determine the acidity order of these ionic liquids and the results are consistent with the catalytic activities observed in the acid-catalyzed probe reactions.

Keywords: Protic ionic liquids; 2-Methylpyridinium; Hammett acidity; Brønsted acidity; Acid catalysis

★★★☆☆ Duan ZY,Gu YL,Zhang J,et al. Protic Pyridinium Ionic Liquids: Synthesis, Acidity Determination And Their Performances For Acid Catalysis[J]. Journal Of Molecular Catalysis A: Chemical,2006,250:163-168.