The Hofmann degradation reaction (also called the Hofmann rearrangement) is an organic reaction in which a primary amide is converted into a primary amine with one carbon atom fewer.
Key Features
- Starting compound: Primary amide (–CONH₂).
- Reagent: Bromine (Br₂) or chlorine (Cl₂) with a strong base (usually NaOH or KOH).
- Product: Primary amine (–NH₂) with one fewer carbon atom.
- By-products: Carbon dioxide and salts (like sodium bromide).
General Idea
- The carbonyl carbon of the amide is lost as carbon dioxide.
- The nitrogen atom stays and becomes part of the new primary amine.
Stepwise Mechanism (Simple Explanation)
- Halogenation – The amide reacts with bromine (or chlorine) in base, forming an N-haloamide.
- Deprotonation and Rearrangement – The nitrogen group shifts, and the carbonyl carbon is expelled as carbonate.
- Formation of Amine – The rearranged intermediate reacts with water, producing the primary amine.
Example
- If you start with acetamide (CH₃–CONH₂), Hofmann degradation produces methylamine (CH₃–NH₂).
- Notice that the carbonyl carbon (C=O) is lost.
Applications
- Laboratory synthesis of primary amines.
- Useful in reducing the carbon chain by one unit (“chain-shortening reaction”).
- Applied in pharmaceutical and dye synthesis where smaller amines are needed.
In short:
The Hofmann degradation is a reaction where primary amides are converted into primary amines with one less carbon atom, using halogen (Br₂/Cl₂) and a strong base.