SO3H-functionalized ionic liquids for selective alkylation of m-cresol with tert-butanol

The SO3H-functionalized ionic liquids were synthesized by using tri-alkylamine and 1,4-butanesultone as the source, and characterized by NMR and TOF-MS, and their catalytic performance for the tert-butylation of m-cresol with tert-butanol (TBA) were investigated. The reaction time, reaction temperature, molar ratio of m-cresol to TBA, and the recycle number of the spent ionic liquid were examined. Under optimum reaction conditions, the conversion of m-cresol and the selectivity to 2-tert-butyl-5-methyl phenol (2-TBC) were 81% and 96%, respectively. No apparent loss of activity and selectivity of the ionic liquid were observed after four recycles. The acidity of ionic liquids determined by Hammett method is about the same as that of conventional acid, such as H2SO4. The possible mechanism for this reaction system was discussed based on the reaction results and the ab initio calculation results.