The effect of pressure on the rate of the benzidine rearrangement III : 2,2'-dibromohydrazobenzene

Abstract

The rates of the acid-catalysed rearrangement of 2, 2'-dibromohydrazobenzene in aqueous ethanol (85 vol% EtOH) have been measured at pressures up to 3, 000 kg/cm^2. It was observed that two different reaction: one is of first order with respect to [HCl] (one-proton mechanism), and the other is of second order (two-proton mechanism), occurred concurrently and the former was strongly accelerated by pressure. From the values of volumes, energies and entropies of activation ; ΔV_1≠=-10.7 cc/mole, E_1≠=16.3 kcal/mole, ΔS_1≠=-34 e.u. for the one-proton mechanism and ΔV_2≠=-0.4 cc/mole, E_2≠=29 kcal/mole, ΔS_2≠=7.3 e.u. for the two-proton mechanism, the transition states of the both mechanisms were discussed.