Catalytic hydrogenation of the C=N bond 3. Hydrogenation of the salicylidene schiff bases and the temperature variation of the rates of hydrogenation of certain azomethines

Abstract

1. Study has been made of the catalytic hydrogenation of salicylidene azomethines in ethanol containing 5% Pd/C at 20°C. It has been shown that C=N bond hydrogenation is not accompanied by hydrolysis and hydrogenolysis, possibly because of intramolecular hydrogen bonding in these compounds. 2. The introduction of hydroxy groups in the o-position of the aldehyde ring reduces the rate of azomethine hydrogenation. The introduction of electron-donor substituants into the p and m positions in the amine ring brings about an insignificant reduction in the hydrogenation rate, while substitution in the o position of the amine ring increases it somewhat. 3. Introduction of electron donor substituants into the amine ring reduces the azomethine hydrogenation, activation energy slightly. Substitution into the aldehyde ring markedly reduces the activation energy in the case of the p-methoxy group, and increases it in the case of the o-hydroxy group.