Liquid-Phase Hydrogenation of 2-Nitro-2'-hydroxy-5'-methylazobenzene on Raney Nickel at Low Temperatures

摘要

The character of changes in the concentrations of intermediate products at the initial stage of the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene (I) on Raney nickel at 275 K and the reasons for their dependence on the composition of the solvent were determined. The smallest amount of I and the largest yield of substituted benzotriazole N-oxide were obtained when the reaction was conducted in a 2-propanol-water solvent containing sodium hydroxide. Conversely, the addition of acids to the solvent sharply increased the yield of the nitrohydrazo derivative. The selectivity of hydrogenation with respect to the substituted benzotriazole was determined by the ratio between the rales of hydrogenation of the nitro and azo groups in the initial compound and intramolecular homogeneous rearrangements ofinter-mediate products.