MolSynapsequestion bank
MolSynapse / Question bank / Amines and Aromatic Nitrogen Compounds / Preparation of amines: Gabriel, Hofmann bromamide, reduction routes
JEE Advanced levelSingle correct optionDifficulty 3 of 3nc012

(R)-2-Methylbutanamide, , is treated with . The chiral product is:

  1. A(R)-butan-2-amine, formed with retention of configuration
  2. Bracemic butan-2-amine
  3. C(S)-butan-2-amine, formed with inversion of configuration
  4. D(R)-pentan-2-amine

Answer: A

In the Hofmann degradation the alkyl group migrates from carbon to nitrogen in the isocyanate-forming step with retention of configuration, and the stereocentre is never broken. The amide group is replaced by at the same position. In both compounds the priority order is (\ce{CONH2} in the amide, \ce{NH2} in the amine) ethyl methyl H, so the descriptor stays R. The carbon count falls by one, giving butan-2-amine.
Practice Amines and Aromatic Nitrogen Compounds More on Preparation of amines: Gabriel, Hofmann bromamide, reduction routes
Previous questionNext question

More questions on Preparation of amines: Gabriel, Hofmann bromamide, reduction routes