Kinetic study on the alkaline hydrolysis of 1‐aryl‐2‐phenyl‐2‐imidazolines. Basicity‐rate of hydrolysis and structure relationships

Abstract

Abstract Rate constants (k obs ) of hydrolysis in boiling alkaline ethanolic solution for six 1‐aryl‐2‐phenyl‐2‐imidazolines were determined. The influence of substituents in the phenyl group at N‐1 upon rate of hydrolysis was studied. When the imidazoline ring is considered to be a substituent of the benzene ring at N‐1, a good correlation with the Hammett equation is found. It was observed that reaction rates were enhanced by electron‐releasing phenyl substituents of N‐1 and reduced by electron‐withdrawing groups, providing a change in the mechanism of the reaction in the first case that was not observed in the second. Agreement with the Hammett equation allowed comparison between experimental and “calculated” rate constants which are nearly equal. An equation relating the rate constants with the ionization constants of imidazolinium ions is given.