Phenylureas. Part 1. Mechanism of the basic hydrolysis of phenylureas

摘要

The mechanism of the hydrolytic decomposition of phenylureas in basic media in the pH range 12 to 14 isninvestigated. In this pH range a levelling of the rate–pH curve is observed as well as a change of the substituentninfluence on the hydrolysis rate. These experimental findings suggest the formation of an unreactive side productnof the phenylurea in a parasitic side equilibrium at sufficiently high pH. The urea dissociates at the aryl–NH groupnto give its conjugate base. For the hydrolytic decomposition of phenylureas an addition–elimination mechanism isnproposed as has been established for the alkaline hydrolysis of carboxylic acid esters and amides.