Effects of organic salts on the rate of intramolecular general base-catalyzed piperidinolysis of ionized phenyl salicylate in the presence of cationic micelles

Abstract

Pseudo-first-order rate constants (kobs), obtained for the cleavage of ionized phenyl salicylate (PS−) at constant [NaOH], [MeCN], [CTABr]T (total concentration of cetyltrimethylammonium bromide), [Pip]T (total concentration of piperidine) and varying concentrations of sodium o-, m- and p-toluate ([MX]), follow the relationship: kobs = (k0 + θK[MX])/(1 + K[MX]), where θ and K are empirical parameters. The values of θ are almost independent of [CTABr]T, while the K values decrease with increasing [CTABr]T within its range 0.005–0.020 mol dm−3. The values of θ and K are explained in terms of a pseudophase model of the micelle coupled with an empirical relationship: KS = KS0/(1 + kX/S[MX]), where KS is the CTABr micellar binding constant of PS− in the presence of MX. The value of KX/S, for the o-toluate ion is nearly 2.5-fold smaller than those for the m- and p-toluate ions. The values of θ/(knW[Pip]T) {where knW[Pip]T = kobs at [CTABr]T = [MX] = 0} vary from nearly 0.5 to 0.6 within the [CTABr]T range 0.005–0.020 mol dm−3.