Mechanism of benzidine and semidine rearrangements. Part XIX. Kinetics and products of the acid conversion of 2,2′-difluorohydrazobenzene

Abstract

The acid conversion of 2,2′-difluorohydrazobenzene in ‘60%’ aqueous dioxan at 25° is of first order in the hydrazo-compound and second order in hydrogen ions. The reaction is slower by a factor of 640 than the acid conversion in like conditions of hydrazobenzene, which has the same kinetic form. The sole rearrangement product from 2,2′-difluorohydrazobenzene is 3,3′-difluorobenzidine, 86 mol.% of which is formed in the conditions. The products of disproportionation accounted for the balance of the material, and, as analytically determined, they comprised 7 mol.% 2,2′-difluoroazobenzene and 2 × 6 mol. of 2-fluoroaniline. It is suggested that the thermodynamic effects of halogen substituents on aniline bases may be taken as a guide to the interpretation of their kinetic effects in benzidine rearrangements.