カチオン界面活性剤非水溶液における脂肪酸エステルのアミノリシス

抄録

Aminolysis of p-nitrophenyl acetate (PNPA), p-nitrophenyl laurate (PNPL), phenyl acetate (PA), methyl acetylsalicylate (AMS), and ethyl benzoate (EB) catalyzed by dodecylammonium propionate (DAP) and monoethanolammonium dodecanoate (EAD) was studied in various apolar solvents. The dependence of pseoud-first order rate constants (κ_obs) on the concentration of surfactants in the micellarsystems differed markedly by the combination of the kinds of esters and the surfactants, while all kobsincreased linearly up to the cmc of surfactants in particular slopes. The extent of rate-enhancement was order of PNPA>>PNPL>PA≈AMS>EB in DAP/cyclohexane systems and of heptane>cyclohexane>benzene in PNPA/DAP systems. Further, the thermodynamic quantities of activation in both the monomer and micellar systems were evaluated from the temperature dependence of the rate constants. Remarkable decrease in the entropy of activation was observed and the results were compared with that in the hydrolysis of PNPA by aqueous micellar catalyst or that in the deacetylation of acetyl-enzyme (α-chymotrypsine) by α-chymotrypsine.