Hofmann rearrangement

Hofmann rearrangement
Named after	August Wilhelm von Hofmann
Reaction type	Rearrangement reaction
Identifiers
RSC ontology ID	RXNO:0000410

The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atoms.

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

The reaction of bromine with sodium hydroxide forms sodium hypobromite in situ, which transforms the primary amide into an intermediate isocyanate. The formation of an intermediate nitrene is not possible because it implies also the formation of an hydroxamic acid as a byproduct, which has never been observed. The intermediate isocyanate is hydrolyzed to a primary amine, giving off carbon dioxide.

Several reagents can substitute for bromine. Sodium hypochlorite,Lead tetraacetate,N-bromosuccinimide, (bis(trifluoroacetoxy)iodo)benzene, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) can affect a Hofmann rearrangement. In the following example, the intermediate isocyanate is trapped by methanol, forming a carbamate.

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