Bechamp reaction

For Bechamp reduction of aromatic nitro compounds, see Bechamp reduction.

In organic synthesis the Béchamp reaction is used for producing arsonic acids from activated aromatic substrates. The reaction is an electrophilic aromatic substitution, using arsenic acid as the electrophile. The reaction proceeds according to this idealized stoichiometry for the preparation of arsanilic acid:^[1]

C₆H₅NH₂ + H₃AsO₄ → H₂O₃AsC₆H₄NH₂ + H₂O

Reaction scope

The reaction was first reported in 1863 by Antoine Béchamp.^[2][3] It is very analogous to the sulfonation of arenes.

The Béchamp reaction was employed in the Nobel Prize-winning work on organoarsenicals by Paul Erlich.^[4]

In one commercial application, the Béchamp reaction is reaction is used to produce roxarsone, which exhibits an anticoccidial action and promotes growth in animals.^[5]

Further reading

• H. P. Brown & C. S. Hamilton (1934). "Naphthalenearsonic Acids. The Application of the Béchamp Reaction to α-Naphthylamine". J. Am. Chem. Soc. 56: 151. doi:10.1021/ja01316a047.