Hofmann reaction

What is Hofmann reaction?

The Hofmann reaction, also known as the Hofmann degradation, or Hofmann degradation of amides or Hofmann rearrangement, is a chemical process that transforms primary carboxylic amides into primary amines with one fewer carbon atom. Discovered by Hofmann in 1881, this reaction is typically achieved through the use of hypohalites or hydroxide, resulting in the formation of an intermediate isocyanate. Heat is required for the reaction, and cyanate may be formed as a byproduct.

Hofmann reaction - Hofmann degradation of amides - Hofmann rearrangement - Hofmann degradation
Hofmann reaction

When carboxylic amides with α-halogen are used, some ketones may also be produced. This reaction is often employed to remove a single carbon atom from a chain while retaining the configuration of the hydrocarbon chain during migration.

Notably, the corresponding amide of pyrazine-2,5-dicarboxylic acid is stable towards both hypochlorous HOCl and hypobromous acids HOBr.

References

Hofmann, A.W. (1881), Ueber die Einwirkung des Broms in alkalischer Lösung auf Amide.  [On the effect of bromine in alkaline solution on amides.] Ber. Dtsch. Chem. Ges., 14: 2725-2736. https://doi.org/10.1002/cber.188101402242

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