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 (k(obs)), obtained for the cleavage of io nized phenyl salicylate (PS-) at constant [NaOH]; [C6H5COONa]; [MeCN]; [CTA Br](T) (total concentration of cetyltrimethylammonium bromide) and varying concentrations of n-butylamine and piperidine ([Am](T)), follow the relatio nship: k(obs) = k(0) + k(n)(obs)[Am](T). The values of k(0) and k(n)(obs) a t different [CTABr](T) and [C6H5COONa] are explained in terms of pseudophas e model of micelle coupled with an empirical relationship: K-S = K-S(0)/(1 + psi[C6H5COONa]) where K-S is the CTABr micellar binding constant of PS-. The calculated respective values of k(M)(ns)K(N) (where K-N is the micellar binding constant of amine and k(M)(ns) = k(M)(n)/V-M with k(M)(n) and V-M representing nucleophilic second-order rate constant for the reaction of am ine with PS- in the micellar pseudophase and micellar molar volume, respect ively) and psi are (12.2 +/- 0.6) x 10 (-3) M (-1) s (-1) and 127 +/- 10 M (-1) for n-butylamine and (14.8 +/- 1.7) x 10 (-3) M (-1) s (-1) and 124 +/ - 5 M (-1) for piperidine. The values of K-N for both amines turn out to be so small that they could not be determined kinetically. The values of k(0) for n-butylamine are relatively more reliable and these k(0) values yield k(M)(h) (pseudo-first-order rate constant for hydrolysis of PS- in the mice llar pseudophase) and psi as (7.0 +/- 1.9) x 10 (-5) s (-1) and 104 +/- 21 M (-1), respectively. (C) 2000 Elsevier Science B.V. All rights reserved.