Béchamp reduction

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For method to prepare aromatic arsonic acids, see Bechamp reaction.
Bechamp reduction
Named after Antoine Béchamp
Reaction type Organic redox reaction
Identifiers
RSC ontology ID RXNO:0000498

The Béchamp reduction (or Béchamp process) is a

aromatic nitro compounds to their corresponding anilines using iron as the reductant:[1]

4 C6H5NO2 + 9 Fe + 4 H2O → 4 C6H5NH2 + 3 Fe3O4

This reaction was once a major route to aniline, but

catalytic hydrogenation is the preferred method.[2]

Reaction history and scope

Main article: Reduction of nitro compounds

The reaction was first used by

Aliphatic nitro compounds are however more difficult to reduce, often remaining as the hydroxylamine. Tertiary aliphatic nitro compounds, however, are converted in good yield to the amine using the Béchamp reduction.[6]

The reduction proceeds in a multistep manner. First, the nitro group is reduced to nitroso, which undergoes hydrogenation to a hydroxylamino group prior to further reduction to the amine.[7]

Proposed mechanism of the Bechamp reduction
Proposed mechanism of the Bechamp reduction

Laux process

The traditional Béchamp reduction cogenerates gray-black iron oxides. The Laux process is based on the finding that the oxide coproduct is strongly affected by various additives, such as

ferrous chloride, aluminium chloride, and even simply sulfuric acid, which are added before heating the iron-nitrobenzene mixture. The innovations from Laux have shifted the emphasis of the Béchamp reduction for the manufacture of anilines to the production of valuable iron oxide pigments.[8] The method is still effective for reduction of nitroaromatics.[9]

Further reading

  • Organic Reactions 2, 428 (1944)

References

  1. ISBN 978-3527306732
    .
  2. ISBN 978-0-8247-2481-8
    .
  3. ^ Béchamp, Antoine (1854). "De l'action des protosels de fer sur la nitronaphtaline et la nitrobenzine. nouvelle méthode de formation des bases organiques artificielles de Zinin". Annales de chimie et de physique. 42: 186–196.
  4. doi:10.15227/orgsyn.040.0005
    .
  5. doi:10.15227/orgsyn.046.0085
    .
  6. doi:10.1039/c4ra00332b. Archived from the original
    (PDF) on 12 February 2023. Retrieved 29 April 2022.
  7. ISBN 9780470638859
    .
  8. ISBN 978-3527306732
    .
  9. doi:10.15227/orgsyn.011.0032
    .
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