Synthesis of hippuric acid with inverse phase transfer catalyst in a heterogeneous liquid-liquid reaction system

Abstract

The synthesis of hippuric acid from benzoyl chloride and glycine in the presence of 4-dimethylaminopyridine as an inverse phase transfer catalyst was carried out in heterogeneous liquid-liquid reaction system using an agitated vessel with a flat interface. By this synthetic technique, the hippuric acid of high product yield could be obtained without the addition of alkali. The observed overall reaction rates were proportional to the interfacial concentration of salt, 1-benzoyl-4-dimethylaminopyridinium chloride in the aqueous phase, which is formed by the reaction between benzoyl chloride and 4-dimethyl-aminopyridine in the organic phase. The overall reaction rates could be reasonably explained by the proposed theoretical model for the inverse phase transfer catalysis considering the mass transfer resistance of relevant reaction species. The reaction rate constant evaluated by fitting the rate data to the model prediction was 6.50 m 3 / (kmol s) at 303 K.