Phenylhydrazine has been prepared by the reduction of benzene diazonium
salts with sulfites;[1] by the reduction of benzene diazonium
chloride with stannous chloride;[2] by the reduction of benzene
diazonium hydrate with zinc or sulfur dioxide;[3] by the reduction
of sodium benzene diazotate with sodium stannite;[4] by the reduction
of diazoamino benzene;[5] by the reduction of nitrosophenyl
hydroxylamine or its methyl ether;[6] and by the action of hydrazine
hydrate on phenol.[7]
[1] Ann. 190, 79 (3878); Ber. 20, 2463, (1887).
[2] Ber. 16, 2976 (1883); 17, 572, footnote (1884).
[3] Ber. 31, 346 (1898).
[4] Ber. 36, 816 (1903).
[5] Ber. 31, 582 (1898).
[6] Ann. 190, 77 (1878).
[7] Ber. 31, 2910 (1898).
The most feasible method consists in the reduction of diazonium
salts with sodium sulfite. Although this method is given in several
laboratory manuals, the results were not found entirely satisfactory.
The present directions provide for a lengthy but essential
heating of the diazonium-sulfite mixture, omit the useless zinc
dust reduction, and supply exact details for preparation on a fairly
large laboratory scale.