Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Amines

Question:

Hoffmann bromamide degradation method is used for preparation of

Options:

Primary amines

Secondary amines

Tertiary amines

Both Primary and Secondary amines

Correct Answer:

Primary amines

Explanation:

The correct answer is Option (1) → Primary amines

The Hofmann bromamide degradation (also called Hofmann rearrangement) is a classic method used specifically for the preparation of primary amines (R–NH₂) from primary amides (R–CONH₂).

Reaction: R–CO–NH₂ + Br₂ + 4 KOH → R–NH₂ + K₂CO₃ + 2 KBr + 2 H₂O

Key features:

  • One carbon atom is lost (the carbonyl carbon of the amide becomes CO₃²⁻).
  • The resulting amine has one less carbon than the original amide.
  • Only primary amines with the –NH₂ group are formed.
  • No secondary or tertiary amines are produced.

Example:

CH₃CONH₂ (acetamide) → CH₃NH₂ (methylamine)

Why the other options are wrong:

  • Secondary amines → Prepared by other methods (e.g., reductive amination, alkylation).
  • Tertiary amines → Not formed in this reaction.
  • Both primary and secondary → Incorrect; only primary amines are formed.