Micellar kinetics of hydrolysis of hydroxamic acids in zwitterionic sulfobetaine surfactants

The effect of zwitterionic micelles of dodecyldimethylammonio-propane-sulfonate (SB3-12) and hexadecyl-dimethyl-ammonio-propanesulfonate (SB3-16) [CnH2n+1N+Me2(CH2)3SO3−, SB3-n, n=12, 16] on the acid and alkaline hydrolyses of some C- and N-substituted hydroxamic acids (RCON(OH)R′) have been studied at 55°C in 5% (v/v) dioxane medium. For acid hydrolysis zwitterionic micelles inhibit the reaction whereas for alkaline hydrolysis, zwitterionic micelles accelerate the rate of hydrolysis. Kinetic data corresponding to the reaction with micelles are analyzed by using the Menger and Portnoy model. Binding constant and first order rate constant for the reaction in micellar pseudophase and in water obtained from kinetic analysis, are reported.