Catalysis of carbaryl hydrolysis in micellar solutions of cetyltrimethylammonium bromide.

Abstract

Carbaryl hydrolysis was studied in micellar solutions of cetyltrimethylammonium bromide (CTAB) at pH 7.5 The hydrolysis followed first-order kinetics with respect to carbaryl concentration. Above the critical micelle concentration (CMC) the rate of hydrolysis increased with increasing CTAB concentration. A plateau was ultimately reached, at which the rate constant was 30 times the rate constant in an equivalent solution without CTAB. Entropies of activation were calculated to prove that the reaction mechanism did not change in the micellar environment. The binding constant of the micelle for carbaryl and the rate constant in the micellar pseudophase were determined from kinetic data using the pseudophase model. To verify this binding constant, a study of the solubility of carbaryl in CTAB solutions was performed. The results were found to be in very good agreement with those from the kinetic studies.