Question

An organic primary amide is treated with bromine (\( \text{Br}_2 \)) and an aqueous solution of sodium hydroxide (\( \text{NaOH} \)) to yield a primary amine. Which of the following statements correctly describes this transformation (Hofmann Bromamide Degradation)?

• A. The resulting primary amine contains one more carbon atom than the starting amide.
• B. The resulting primary amine contains the exact same number of carbon atoms as the starting amide.
• C. The resulting primary amine contains one less carbon atom than the starting amide due to the loss of the carbonyl group as a carbonate ion.
• D. The reaction converts a secondary amide into a tertiary amine via a molecular rearrangement.

Hint:

Hofmann Bromamide Degradation is a vital tool for organic "step-down" convergence conversions. For example, treating Ethanamide (\(\text{CH}_3\text{CONH}_2\)) under these reaction conditions skips the carbonyl group entirely to produce Methanamine (\(\text{CH}_3\text{NH}_2\)).

Answer 1

The Correct Option is C

Concept: The Hofmann Bromamide Degradation Reaction is a classic step-down degradation method used in organic synthesis to convert a primary amide into a primary amine with a shorter carbon chain length. The general chemical equation is: \[ R-\text{CONH}_2 + \text{Br}_2 + 4\text{NaOH} \quad \longrightarrow \quad R-\text{NH}_2 + \text{Na}_2\text{CO}_3 + 2\text{NaBr} + 2\text{H}_2\text{O} \]

Step 1: Analyze the migration mechanism of the reaction.
During the reaction pathway, an intermediate *nitrene* or *isocyanate* is generated. The alkyl or aryl group (\(R\)) migrates directly from the carbonyl carbon to the adjacent nitrogen atom.

Step 2: Track the carbon atom balance across the products.
The central carbonyl carbon (\(-\text{C}=\text{O}\)) of the primary amide is completely extruded from the organic chain and eliminated as a mineral byproduct in the form of sodium carbonate (\(\text{Na}_2\text{CO}_3\)). As a direct consequence, the resulting primary amine (\(R-\text{NH}_2\)) contains exactly one less carbon atom than the parent starting amide.