In Conjunction with an attempt to prepare hydrazobenzene by alkaline sulfide reduction of nitrobenzene, the reduction of azoxybenzene, a reduction intermediate, has been studied kinetically under the synthetic conditions. The rates of reduction are markedly affected by the solubility or the dispersibility of azoxybenzene in the solution of reducing agent. During the course of reaction, the product hydra-zobenzene is again oxidized to azobenzene by the disulfide formed through autoxidation of hydrosulfide.
Quinones and aromatic ketones have been found to serve as effective catalysts for the removal of the disulfide formed during the course of alkaline sulfide reduction of azoxybenzene or azobenzene into hydrazobenzene. It seems reasonable to assume that they retarded the oxidation of hydrazobenzene by the disulfide, and furthermore, they acted as hydrogen carriers in the reducion of azobenzene to hydrazobenzene.
Catalytic reduction of N-substituted cyanamides was investigated in order to prepare N-substituted formamidines or other reduction products, which had previously been prepared with difficulty. Methyl-, dimethy l-, and di-n-propyl-cyanamides were reduced to the corresponding formamidines in good yield by using Pd black catalyst in an acid medium. Dimethylformamidine was also obtained by electrolytic reduction of dimethylcyanamide on a Pd cathode.