BENZOQUINONE IMINES .2. HYDROLYSIS OF P-BENZOQUINONE MONOIMINE AND P-BENZOQUINONE DI-IMINE

Kinetic studies of the hydrolysis of p-benzoquinone monoimine, over the pH range 2-10, have shown that the reaction exhibits first-order kinetics over the whole pH range. The pH dependence indicates a rate-controlling step involving the reaction of both the free imine and its protonated form with water, the latter being 1.8 × 103 more reactive than the former. The reaction was found to be catalysed by phosphate ions. Similarly the hydrolysis of p-benzoquinone di-imine involves reaction of the free base and its mono- and di-protonated forms with water. Phosphate ions do not catalyse the reaction, but, in the pH range 5.5-8, polymerisation of the di-imine occurs as a significant side-reaction, even at low concentrations.