Structure-reactivity correlation in the pyridinolysis of substituted phenyl acetates

Abstract

The pyridinolysis of substituted phenyl acetates in acetonitrile was investigated with an electric conductivity method. The rates of these reactions were increased with electron-donating group in pyridine and electron-withdrawing group in phenyl acetate, ϱ x (X;substituents in phenyl ring) values increase gradually according to the electron-donating ability in pyridine substituents, but the |ϱ y|(Y;substituents in pyridine ring) values decrease with that of substituents. The β values increase with increasing electron-withdrawing ability of the substituents in the phenyl ring, it can be inferred that N---C bond formation increases progressively p-methyl to p-nitrophenyl acetates. This is in agreement with prediction of substituent effects for a simple S N2 displacement reaction. The sensitivity parameters, β and ϱ, are inter-related and are themselves sensitive to the reactivity of the system. All above results are interpreted in terms of a dissociative S N2 mechanism involving a metastable tetrahedral intermediate.