Bechamp aromatic nitro compounds

The traditional technique of reducing nitro compounds with iron powder in dilute acid (Bechamps-Brimmeyr reduction) continues to be used for nitro compounds that are adversely affected by the catalytic reduction method with hydrogen. The list of examples includes aromatic nitro compounds carrying halogen substituents, especially if these are attached in ortho or para position to the nitro group. The solution containing only a small amount of acid (such as acetic acid) is almost neutral and allows iron to precipitate as Fe304. 

Bechamp A process for reducing organic nitro-compounds to amines, using iron, ferrous salts, and acetic acid. Invented by A. J. Bechamp in 1854 and still used for making certain aromatic amines. 

The property of being converted by energetic reduction into primary amines belongs to the nitro-compounds both of the aliphatic and of the aromatic series. Six atoms of hydrogen are required for the reduction of each nitro-group. In industry nitrobenzene is reduced, not with expensive tin, but with iron filings or iron powder according to the old method of Bechamp, which is still in use at the present time. The amount of hydrochloric acid indicated by the equation... 

The main method, both in the laboratory and in technical practice, for the introduction of an amino group into an aromatic compound, is nitration and reduction. Reduction of nitro compounds is accomplished by (1) catalytic hydrogenation, (2) iron reduction (Bechamp method), (3) sulfide reduction, or (4) zinc reduction in an alkaline medium. 

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