Ammonium sulfide, reducing agent reduction

Reducing agents commonly employed are iron, tin, or SnCI2 in hydrochloric acid and ammonium or alkali-metal sulfides catalytic hydrogenation and electrolytic reduction also are employed (see Section 23-12B). 

Partial reduction of aromatic polynitro compounds leads to nitro amines. The most successful reagents are the alkali metal or ammonium sulfides in aqueous alcoholIn some instances, sodium bicarbonate combined with sodium sulfide gives better results because of the formation of sodium hydrosulfide, which is believed to be the main reducing agent. Also, aqueous methanol is preferred to aqueous ethanol. Nitro compounds that are sparingly soluble in alcohol solutions may be reduced by hydrogen sulfide in pyridine solution. ... 

About the same time, Zinin, N. (1812-1880) was able, in 1842, to carry out an original synthesis of aniline, that he named benzidam, and of some other aromatic amines by reduction reaction of nitrobenzenes. As for a reducing agent, Zinin utilized a solution of ammonium sulfide to generate molecular hydrogen14,15. 

Under suitable conditions it is possible to isolate the A-substituted hydroxylamines that are formed as intermediates in the reduction of nitro compounds. For this purpose it is essential in the reduction of aromatic nitro compounds to work with neutral or nearly neutral solutions suitable reducing agents are hydrogen and platinum oxide catalysts in glacial acetic acid,82,83 zinc dust in ammonium chloride solution,84 aluminum amalgam,85 and ammonium sulfide.86 Aliphatic nitro compounds may be reduced as their alkali salts (nitronates) by diborane in tetrahydrofuran, then giving A-alkylhydroxyl-amines 87 for instance, A-cyclohexylhydroxylamine is thus obtained from nitrocyclohexane in 53% yield. However, aliphatic nitro compounds are converted into A-alkylhydroxylamines more simply by catalytic hydrogenation in the presence of palladium-barium sulfate unlike aromatic nitro compounds, aliphatic nitro compounds require an acid medium for reduction to hydroxylamines an oxalic acid medium has proved the most suitable. 

Denitration can be effected by chemical reducing agents (134)- For monomolecular nitrates, reductive denitration with hydrogen and Raney nickel (135) is preferable. Ammonium hydrogen sulfide effectively denitrates the nitrated polysaccharides. 

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