Catalytic Action of Imidazole in Nonaqueous Solutions of Nonionic Surfactants

Abstract

In order to examine the catalytic action of imidazole in nonaqueous solutions of nonionic surfactants, the pseudo-first-order rate constants (k_obs) for the reaction between p-nitrophenyl acetate and imidazole in carbon tetrachloride was measured as a function of the concentration of imidazole at fixed molar ratios (0.5, 1.0, 2.0) of imidazole to surfactants. By analyzing of k_obs-[Imidazole] profile obtained, the second and third rate constants (k_{2, m} and k_{3, m}) for imidazole monomer and the catalytic rate constant (k_A) for imidazole aggregates were obtained. Both k_{2, m} and k_A values increase with the increase in the molar ratio or the oxyethylene chain length of surfactants, but the increase is small for k_{2, m}. The catalytic action of imidazole in water solubilized into the imidazole/surfactant/CCl₄ systems is enhanced with decrease in polarity of the interior of aggregates.