Effects of inert organic and inorganic anions on the rates of intramolecular general base-catalyzed reactions of ionized phenyl salicylate (PS-) withpiperidine in the presence of cationic micelles

Pseudo-first-order rate constants (k(obs)) for piperidinolysis of PS- follo w the relationship k(obs) - k(0)= k(n)(obs) [Pip](T) ([Pip](T) = total conc entration of Pip) at a constant [CTABr](T) (total concentration of cetyltri methylammonium bromide), [MX] (inert salt concentration) and 35 degreesC. T he values of k(n)(obs) at different [CTABr]T (ranging from 0.005 to 0.02 M) and [MX] follow the relationship k(n)(obs) = (k(w)(n) + k(w)(n) Psi [MX] KnsM K-N K-S(0)[CTABr](T))/( 1 + Psi [MX] + K-S(0) [CTABr](T)), where k(w) (n) = k(n)(obs) at [CTABr](T) = [MX] = 0, Psi is an empirical parameter and K-S(0) is the CTABr micellar binding constant of PS- in the absence of MX. The magnitude of Psi is attributed to the ability of X- to expel PS- from micellar pseudophase to the aqueous pseudophase. The values of Psi vary in the order Psi (sodium cinnamate) >Psi (sodium 4-methoxybenzoate) >Psi (sodi um 2-chlorobenzoate) >Psi (disodium isophthalate) >Psi (disodium phthalate) >Psi (sodium sulfate) >Psi (disodium fumarate). The values of k(M)(ns) K-N (k(M)(ns) = k(M)(n)/V-M, where k(M)(n) is the second-order rate constant f or the reaction of Pip with PS- in the micellar pseudophase and V-M is the micellar molar volume in M-1 and K-N represents CTABr micellar binding cons tant of Pip) are not significantly affected by the presence of MX into the reaction mixtures. Copyright (C) 2000 John Wiley & Sons, Ltd.