Mechanism of benzidine and semidine rearrangements. Part XVII. Kinetics and products of the acid rearrangements of 2,2′-dimethoxy- and 4-methoxy-hydrazobenzene

Abstract

These rearrangements are both of first-order in hydrazo-compound and of first-order in hydrogen ions over the measured 500- or 700-fold range of hydrogen-ion concentration. The sole rearrangement product from 2,2′-dimethoxyhydrazobenzene is 3,3′-dimethoxybenzidine: a small amount of disproportionation accompanies rearrangement. Kinetically, this disproportionation has the same acid-dependence as the accompanying rearrangement. The main rearrangement product from 4-methoxyhydrazobenzene is an o-semidine; but it is accompanied by a substantial amount of the p-semidine, and by a substantial quantity of the products of disproportionation. The data show that this disproportionation has a kinetic form identical with that of the accompanying rearrangements.