The micelle-catalysed hydrolysis of benzylpenicillin

Micelles of cetyltrimethylammonium bromide catalyse the alkaline hydrolysis of benzylpenicillin with a rate enhancement of ca. 50-fold. However, the rate of reaction is inhibited by increasing concentrations of hydroxide ion and penicillin anion. A saturation phenomenon is observed with increased concentration of surfactant. Attempts are made to determine the binding- and rate-constants using existing kinetic models. These are not completely satisfactory and a model is proposed which assumes that both hydroxide ion and penicillin have to be bound to the micelle for reaction to occur. Bromide, chloride, acetate, fluoride, and benzylpenicilloate ions all inhibit the micellar catalysis.