Reduction of nitro compounds


The reduction of nitro compounds are chemical reactions of wide interest in organic chemistry. The conversion can be affected by many reagents. The nitro group was one of the first functional groups to be reduced. Alkyl and aryl nitro compounds behave differently. Most useful is the reduction of aryl nitro compounds.

Aromatic nitro compounds

Reduction to anilines

The reduction of nitroaromatics is conducted on an industrial scale. Many methods exist, such as:
Metal hydrides are typically not used to reduce aryl nitro compounds to anilines because they tend to produce azo compounds.

Reduction to hydroxylamines

Several methods have been described for the production of aryl hydroxylamines from aryl nitro compounds:
Treatment of nitroarenes with excess zinc metal results in the formation of N,''N'''-diarylhydrazine.

Reduction to azo compounds

Treatment of aromatic nitro compounds with metal hydrides gives good yields of azo compounds. For example, one could use:

Reduction to hydrocarbons

Hydrodenitration is difficult to achieve but can be affected by catalytic hydrogenation over platinum on silica gel at high temperatures.
The reaction can also be effected through radical reaction with tributyltin hydride and a radical initiator, AIBN as an example.

Reduction to amines

Aliphatic nitro compounds can be reduced to aliphatic amines by several reagents:
α,β-Unsaturated nitro compounds can be reduced to saturated amines by:
Aliphatic nitro compounds can be reduced to aliphatic hydroxylamines using diborane.
The reaction can also be carried out with zinc dust and ammonium chloride:

Reduction to oximes

Nitro compounds are typically reduced to oximes using metal salts, such as tin chloride or chromium chloride. Additionally, catalytic hydrogenation using a controlled amount of hydrogen can generate oximes.