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

摘要

Pseudo-first-order rate constants (k_obs), 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: k_obs = (k_0 + #theta# 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 #theta# and K are explained in terms of a pseudophase model of the micelle coupled with an empirical relationsphip: K_S = K_S~0/(1 + k_X/S[MX]), where K_S is the CTABr micellar binding constant of PS~- in the presence of MX. The value of K_X/S, for the o-toluate ion is nearly 2.5-fold smaller than those for the m-and p-toluate ions. The values of #theta#/(k_w~n[Pip]_T) {where k_w~n[Pip]_T = k_obs 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).