A Kinetic Study of the Metal Ion-catalyzed Glycolysis of Benzonitrile

Abstract

Abstract The kinetics of the lead ion-catalyzed glycolysis of benzonitrile were studied in the presence of water. The experimental results indicated that the rate of the formation of ammonia followed the first-order rate law with respect to the concentrations of benzonitrile and of water. For the concentration of the catalyst, the rate found was of a 0.44 order. It was observed that the product, β-hydroxyethyl benzoate, exhibited an inhibiting effect on the glycolysis. The effects of substituents on benzonitrile were found to fit the Hammett rule. The reaction was remarkably influenced by the type of glycol used. The reaction also proceeded through the hydrolysis of benzonitrile, followed by the glycolysis of the benzamide thus formed. The rate of the glycolysis of benzamide was about one-third that of benzonitrile, which is the main reaction in the system. The reaction of imidate formation possessed a small equilibrium constant at a high temperature, but it had a high reaction rate. The proposed mechanism for these glycolysis reactions is as follows: the addition of glycol to benzonitrile yields imidate, which then forms a chelate compound with a metal ion. The imidate activated by the formation of the chelate is easily hydrolyzed by water to form ester and ammonia. This ester tends to chelate to the metal ion and so inhibits the reaction.