Alkaline hydrolysis of dibenzoylaminonaphthalenes in 70%(v/v) Me2SO–H2O and the effect of a neighbouring amide group

Abstract

The rate of hydrolysis of 1-benzoylamino-8-dibenzoylaminonapthalene to 1,8-bis(benzoylamino) naphthalene in 70%(v/v) Me₂SO–H₂O is independent of hydroxide ion concentration in the range 0.001–0.2 mol dm^–3. For 1-benzoylamino-8-dibenzoylamino-2,7-dimethoxynaphthalene the observed rate coefficients show a curvilinear dependence on hydroxide ion concentration. The order of reaction with respect to hydroxide ion changes from first order to zero order as the concentration is increased. The complex dependence on hydroxide ion concentration is due to ionisation of the 1-benzoylamino groups and equilibrium constants for the ionisation have been determined in separate experiments before appreciable hydrolysis has taken place. The kinetics for both imides can be explained by a mechanism involving reaction of undissociated 1-benzoylamino-8-dibenzoylaminonaphthalene with hydroxide ion or by reaction of the dissociated species with solvent. For the latter process the magnitude of the rate coefficient in comparison with that for the spontaneous solvolysis of 1-dibenzoylaminonaphthalene requires that the ionised amide group is involved as an intramolecular base catalyst in assisting the attack of solvent.