Benzoquinone imines. Part 18. Kinetics and mechanism of oxidative coupling reactions involving N,N-bis-(2-hydroxyethyl)-p-phenylenediamine

Abstract

A kinetic and mechanistic study of oxidative coupling reactions of N,N-bis-(2-hydroxyethyl)-p-phenylenediamine with m-phenylenediamines, phenols, and acetoacetanilide is described. The reactions involve the rapid establishment of an equilibrium between N,N-bis-(2-hydroxyethyl)-p-benzoquinone di-imine and a hydroxy-amine intermediate (3). Competition between direct coupling of N,N-bis-(2-hydroxyethyl)-p-benzoquinone di-imine and hydrolysis to p-benzoquinone monomine via(3) with subsequent coupling leads to a mixture of two dye products. The relative yields are dependent on pH and coupler concentration. Kinetic evidence for the formation of the intermediate (3) is presented.