Hofmann rearrangement

The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atom.^[1][2][3]

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The reaction of bromine with sodium hydroxide forms sodium hypobromite in situ, which transforms the primary amide into an intermediate isocyanate. The intermediate isocyanate is hydrolyzed to a primary amine giving off carbon dioxide.

The reaction is named after its discoverer: August Wilhelm von Hofmann. This reaction is also sometimes called the Hofmann degradation, and should not be confused with the Hofmann elimination.

Variations

Several reagents can substitute for bromine. N-Bromosuccinimide and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) can effect a Hofmann rearrangement. In the following example, the intermediate isocyanate is trapped by methanol forming a carbamate.^[4]

A mild alternative to bromine is also (bis(trifluoroacetoxy)iodo)benzene.^[5]

References

See also

• Curtius rearrangement
• Iodoform reaction
• Lossen rearrangement
• Schmidt reaction
• Weerman degradation