Kinetic Study on the Effects of Sodium Benzoate on Piperidinolysis of Phenyl Salicylate in Alkaline Pure Cationic and Mixed Cationic-Nonionic Micelles

Pseudo-first-order rate constants (k(obs)) for piperidinolysis of ionized phenyl salicylate (PS(-)), obtained at 0.1 M piperidine (Pip), constant concentration of pure CTABr as well as mixed CTABr-C(12)E(23) micelles and varying values of [C(6)H(5)CO(2)Na], follow the empirical relationship: k(obs) = (k(0) + theta K(X/S)[MX])/(1 + K(X/S)[MX]) where theta and K(X/S) are empirical constants, MX = C(6)H(5)CO(2)Na and k(0) = k(obs) at [MX] = 0. The values of theta and K(X/S) are explained in terms of pseudophase micellar (PM) model coupled with an empirical relationship: K(S) = K(S)(0)/(1 + K(X/S)[MX]) where K(X/S) is an empirical constant as well as K(S) and K(S)(0) are CTABr micellar binding constants of PS(-) (i.e., S = PS(-)) in the presence and absence of MX, respectively.