Concept Explanation: Hofmann Bromamide Reaction

The Hofmann bromamide reaction is a chemical process where a primary amide is converted into a primary amine with one less carbon atom. This reaction involves treating the amide with bromine and a strong base (like NaOH or KOH). The key steps include the formation of an isocyanate intermediate, which then rearranges and hydrolyzes to yield the amine.

Step-by-Step Mechanism:

Step 1: The amide reacts with bromine and base to form an N-bromoamide.

R - C (= O) - N H_{2} + B r_{2} + NaOH \to R - C (= O) - N H B r + NaBr + H_{2} O

Step 2: The N-bromoamide loses a proton to form a bromoamide anion, which rearranges to an isocyanate.

R - C (= O) - N H B r + O H^{-} \to R - C (= O) - N^{-} B r \to R - N = C = O

Step 3: The isocyanate hydrolyzes to form a primary amine and carbon dioxide.

R - N = C = O + H_{2} O \to R - N H_{2} + C O_{2}

In the given image, the starting material is Ph-CH₂-CONH₂ (phenylacetamide). After Hofmann bromamide reaction, it loses one carbon atom and forms Ph-NH₂ (aniline).

Final Answer:

Ph – NH₂

Related Topics:

Amines and Amides
Rearrangement Reactions
Degradation Reactions
Organic Synthesis

Formulae and Theory:

General Reaction:

R - C O N H_{2} + B r_{2} + 4 N a O H \to R - N H_{2} + 2 N a B r + N a_{2} C O_{3} + 2 H_{2} O

Key Points: The reaction is used for the preparation of primary amines from amides. It involves the loss of the carbonyl carbon as CO₂, resulting in an amine with one fewer carbon atom. The rearrangement step is crucial and follows the Hofmann rule, which favors the least substituted amine.