Kinetics of oxidative condensation of p-phenylenediamines with mono- and poly-substituted benzoylacetanilides

Abstract

The kinetics of the oxidative condensation of NN-dialkyl-p-phenylenediamines and mono- and poly-substituted benzoylacetanilides in aqueous alkaline solution, in the pH range 7·5–10·8, have been investigated by the stopped-flow technique. In this pH range the rate is proportional to the concentration of the positively charged p-benzoquinone di-imine and of the anion corresponding to the benzoylacetanilide. It is suggested that the rate-determining step is the formation of the leuco-dye. The reactivity of the benzoylacetanilide anions increases with increasing basicity. A linear relationship between log (k_c^–/k_0c^–)(where k_0c^– is the specific rate constant of the unsubstituted benzoylacetanilide) and the σ values of the substituents was obtained for both mono- and poly-substituted benzoylacetanilides.