1.

Explain Hoffmann degradation of amides. OR Write a note on Hoffmann bromide reaction.

Answer»

Solution :The conversion of amides into aminse in the PRESENCE of
bromine and alkali is known as Hoffmann degradation of amides. An
important characteristic of this reaction is that an amine with one
carbon LESS than those in the amide is formed. This reaction is an
example of molecular rearrangement and involves the migration of an
alkyl or aryl group from the carbonyl carbon to the adjacent nitrogen
atom.
For example,
(1) When propanamide is treated with bromine and aqueous or
alcoholic sodium hydroxide, ethanamine is obtained which has one
carbon atom less.
`underset("Propanamide")(CH_(3)-C)H_(2)-overset(overset(O)(||))(C)- NH_(2) + br_(2)+4NaOH rarr`
`underset("Ethanamine")(CH_(3)-C)H_(2)- NH_(2) + Na_(2)CO_(3)+2NaBr+2H_(2)O`
(2) When benzamide is treated with bromine and aqueous of
alcoholic sodium Hydeoside, aniline is obtained.


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