Mechanism of benzidine and semidine rearrangements. Part XX. Kinetics and products of the acid conversions of 2,2′-dichloro-,4-chloro-, and 4,4′-dichloro-hydrazobenzene

Abstract

In ‘60%’ aqueous dioxan at 0° the acid conversion of 2,2′-dichlorohydrazobenzene is much slower than that of the difluoro-analogue but has the same kinetic form : it is of first order in hydrazo-compound and second order in hydrogen ions. Independently of the acidity, this conversion leads to 94% of the corresponding benzidine and 6% of the products of disproportionation. The acid conversion of 4-chlorohydrazobenzene in similar conditions has an identical kinetic form. Independently of the acidity, it gives 19% of the corresponding diphenyline, 30% of the o-semidine, 20% of the p-semidine, and 31% of the products of disproportionation. The acid conversion of 4,4′-dichlorohydrazobenzene also has the same kinetic form. Independently of the acidity, it produces 22% of the o-semidine and 75% of the products of disproportionation. These findings lead to the conclusion that each of the simultaneous reactions of these hydrazo-conversions, whether it leads to a benzidine, a diphenyline, an o-semidine, a p-semidine, or products of disproportionation, has individual kinetics of the same form, viz. of first order in hydrazo-compound and second order in hydrogen ion.