The temperature dependence of the pH-dependence of the hydrolysis of p-nitrophenylacetate catalyzed by 4(β-hydroxyethyl)-imidazole, imidazole-propionic acid, cis- and trans-urocanic acid, mercaptoethanole, cysteamine and mercaptomethyl-imidazole was investigated in order to determine the dissociation energy of the catalytic active group. Bifunctional catalysts like mercaptomethyl-imidazole and mercaptoethanole gave wrong kinetic pk-values and non-linear pk/I/T plots.
