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SolutionsRearrangement Reactions

1. Rearrangement product

  1. Benzamide, Br2, NaOH
  2. Hexanamide, Br2, NaOH
  3. Benzoyl chloride, NaN3; heat; H2O
  1. Aniline.
  2. Pentylamine (one carbon less than the amide).
  3. Aniline, via benzoyl azide and phenyl isocyanate (Curtius rearrangement).

2. Balance the equation

Write the balanced equation for the Hofmann rearrangement of propanamide.

CH3CH2CONH2 + Br2 + 4 NaOH → CH3CH2NH2 + Na2CO3 + 2 NaBr + 2 H2O.

The carbonyl carbon is lost as carbonate: the intermediate isocyanate is hydrolysed to a carbamic acid, which decarboxylates.

3. Configuration

The Hofmann rearrangement of (S)-2-methylbutanamide gives 2-butylamine. With which configuration?

(S)-2-Butylamine: the alkyl group migrates from carbon to nitrogen with retention of configuration, because it never fully leaves the molecule.

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