In order to examine the catalytic action of imidazole in nonaqueous solutions of nonionic surfactants, the pseudo-first-order rate constants (
kobs) 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
kobs-[Imidazole] profile obtained, the second and third rate constants (
k2, m and
k3, m) for imidazole monomer and the catalytic rate constant (
kA) for imidazole aggregates were obtained. Both
k2, m and
kA values increase with the increase in the molar ratio or the oxyethylene chain length of surfactants, but the increase is small for
k2, m. The catalytic action of imidazole in water solubilized into the imidazole/surfactant/CCl
4 systems is enhanced with decrease in polarity of the interior of aggregates.
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