Effects of [C6H5COONa] on rates of intramolecular general base-catalyzed piperidinolysis and n-butylaminolysis of ionized phenyl salicylate in the presence of cationic micelles

Pseudo-first-order rate constants (kobs), obtained for the cleavage of ionized phenyl salicylate (PS−) at constant [NaOH]; [C6H5COONa]; [MeCN]; [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of n-butylamine and piperidine ([Am]T), follow the relationship: kobs=k0+knobs[Am]T. The values of k0 and knobs at different [CTABr]T and [C6H5COONa] are explained in terms of pseudophase model of micelle coupled with an empirical relationship: KS=KS0/(1+ψ[C6H5COONa]) where KS is the CTABr micellar binding constant of PS−. The calculated respective values of knsMKN (where KN is the micellar binding constant of amine and knsM=knM/VM with knM and VM representing nucleophilic second-order rate constant for the reaction of amine with PS− in the micellar pseudophase and micellar molar volume, respectively) and ψ are (12.2±0.6)×10−3 M−1 s−1 and 127±10 M−1 for n-butylamine and (14.8±1.7)×10−3 M−1 s−1 and 124±5 M−1 for piperidine. The values of KN for both amines turn out to be so small that they could not be determined kinetically. The values of k0 for n-butylamine are relatively more reliable and these k0 values yield khM (pseudo-first-order rate constant for hydrolysis of PS− in the micellar pseudophase) and ψ as (7.0±1.9)×10−5 s−1 and 104±21 M−1, respectively.