Comparative Stability of Benzamide, Salicylamide, and Some N-Substituted Derivatives

Abstract

The comparative stability of benzamide, salicylamide, and some N-substituted derivatives were determined in 1.00 N perchloric acid and 1.00 N sodium hydroxide to elucidate the effect of the substituents on the rates of hydrolysis. Results indicated that in both media benzamide was less stable than salicylamide and N-(2-diethylaminoethyl)-benzamide was less stable than the corresponding salicylamide derivative. This clearly demonstrated the marked stabilizing effect of the hydroxyl group in the ortho position. Benzamide and N-(2-diethylaminoethyl) benzamide were less stable in alkaline than in acid medium. An opposite effect was noticed in salicylamide and other N-substituted salicylamide derivatives. This may be due to stability of the phenolate ions due to resonance effect and consequent resistance to nucleophilic attack by hydroxide ions. Substitution of alkyl or aminoalkyl groups on the amide nitrogen markedly increased the stability of salicylamide; a phenyl group on the nitrogen also had a protective effect, but less than that of alkyl or aminoalkyl groups. The inhibitory effect of these substituents on the rate of hydrolysis of salicylamide is presumed to be due to steric hindrance.