Kinetics and mechanisms of decarboxylation of 4-phenylallophanate anions

Abstract

The decarboxylation of a series of 4-phenylallophanate anions has been studied as a function of pH and buffer concentration. A changeover in mechanism is revealed from Hammett and Brønsted correlations, entropy values, and solvent isotope effects. A concerted mechanism in acid and neutral media is proposed, whereas in basic media the results may be explained by a spontaneous decomposition or by a cyclic reaction with involvement of a molecule of water.