A tautomeric catalyst is a molecule that repeatedly cycles between two tautomeric states in the course of catalyzing a chemical reaction. The stoichiometries and kinetics for four different tautomeric catalysts-2pyridone, benzoic acid, pyrazole, and 1,2,4-triazole-were examined for the aminolysis of 4-nitrophenyl acetate by «-butylamine and glycine ethyl ester in benzene and 1.5% methanol-benzene. The rate law is third order, rate = ¿[4-nitrophenyl acetate][amine][catalyst], and conforms to a reaction with the following stoichiometry: 4-nitrophenyl acetate + amine + catalyst -amide + 4-nitrophenoI + catalyst. The rate constants at 25 °for the above four tautomeric catalysts are (a) n-butylamine, 17, >2, 0.21, and 0.87 M~sec-1, respectively, and (b) glycine ethyl ester, 0.80, 0.36, 0.0086, and 0.021 M-2 sec-1, respectively. 2-Aminophenol exhibited no catalytic activity for (7) P.

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summaryA theory of diffusion control within hollow fiber catalysts is derived for three different types of coordinate geometries: Cartesian, cylindrical, and spherical. Effectiveness factors are calculated and formulas for reactant conversion in both a fixed-bed and a contimunuous-feed stirred-tank reactor are derived. The apparent Michselis constant, K,,,', is a measure of the amount of diffusion control within the catalysts. When K,' is equal to K,,,, the true Michaelis constant, there is no diffusion control. In all other cases K,' is greater than K,. Hollow fibers are attractive alternatives to spherical microcapsules for the encapsulation of enzymes.

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