Bechamp reduction

The Béchamp reduction is the oldest reaction in industrial organic chemistry for the production of primary aromatic amines from nitroaromatic compounds by reduction with iron and mineral acids. The Bechamp reduction is now largely replaced by the catalytic hydrogenation, but is still used in particular in the dye industry and for the production of iron oxide pigments.

History

The fact that the reduction of aromatic nitro compounds to the corresponding amines with iron or iron (II ) salts in aqueous hydrochloric acid pathway was discovered in 1854 by Antoine J. Béchamp as a special case of reduction with base metals in acids.

Mechanism

The given reaction equation is contrary to the general process that can be considered as a result of the following reaction steps:

Iron (II ) chloride ( FeCl2 ) is formed continuously from the hydrochloric acid and iron.

Pros and Cons

The most important advantage is the low process costs. Iron is cheap, the resulting iron (II, III ) oxide can be resold as a color pigment and is therefore not to be regarded as waste, but as a product of value. The reaction requires a strict observance carefully elaborated reaction parameters. In large-scale systems, this is easier to control in general as a laboratory scale. The precise elaboration of the method is time-consuming. Laboratory therefore it often reduced catalytically or with other base metals such as zinc.

Another advantage of the method is that the aromatic and double bonds are not hydrogenated.

On an industrial scale, however, often catalytic hydrogenation for the reduction of aromatic nitro compounds to anilines is used today.