The reactivity of nitro and azo groups in liquid-phase hydrogenation of 2-nitro-2 '-hydroxy-5 '-methylazobenzene

The hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene can proceed by the addition of hydrogen at either the nitro group or the azo group of the initial compound. The product of hydrogen addition at the azo group identif ied as 2-nitro-2'-hydroxy-5'-methylhydrazobenzene can transform into substi tuted benzotriazole N-oxide in solution. The ratio between the rates of int ermediate product hydrogenation and rearrangement to benzotriazole determin es the yield of the desired product and depends on the nature and compositi on of the solvent in which the reaction is conducted.