Transesterification of ethyl butyrate with methanol on the organic cation-exchanged mordenite ([bmim]M20) was studied in order to examine the reactivity of the methoxide ions that were generated on [bmim]M20 by the dissociation of methanol Since transesterification occurred by addition of NaCl the methoxide ions on [bmim]M20 were demonstrated to be utilizable in the reaction The activity improved with a concentration of NaCl below 3 mmol L-1 whereas it was constant at concentrations above 3 mmol L-1 The adsorption of ethyl butyrate on the partially ion-exchanged [bmim]M20 samples was observed by FT-IR spectroscopy It was found that it was difficult for ethyl butyrate to enter the micro-pores of [bmim]M20 From these results a reaction mechanism was proposed in which the methoxide ions generated in the micropores of [bmim]M20 reacted with ethyl butyrate after they diffused outside of the micropores (C) 2010 Elsevier B V All rights reserved