Question

Consider the following reactions giving major product. Identify the correct reaction. 

• A. Reaction 1
• B. Reaction 2
• C. Reaction 3
• D. Reaction 4

Hint:

Hofmann bromamide reaction is identified by loss of one carbon atom when an amide is converted into a primary amine.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Let's analyze the validity of each reaction pathway provided in the options.
Step 2: Detailed Explanation:
1. Reaction 1: Gabriel phthalimide synthesis is used to prepare primary aliphatic amines. Aryl halides like chlorobenzene do not undergo nucleophilic substitution with the phthalimide ion because of the partial double bond character of the C-X bond and electronic repulsion. Thus, aniline cannot be prepared this way.
2. Reaction 2: Benzylamine (\( \text{Ph}-\text{CH}_2\text{NH}_2 \)) reacts with \( \text{CHCl}_3/\text{KOH} \) (Carbylamine reaction) to form benzyl isocyanide (\( \text{Ph}-\text{CH}_2\text{NC} \)). Reduction of isocyanides with \( \text{Sn}/\text{HCl} \) or \( \text{LiAlH}_4 \) yields secondary methyl amines (\( \text{Ph}-\text{CH}_2\text{NHCH}_3 \)), not the starting primary amine.
3. Reaction 3: Nitration of acetanilide with \( \text{HNO}_3/\text{H}_2\text{SO}_4 \) gives \( p \)-nitroacetanilide as the major product because the acetamido group (\( -\text{NHCOCH}_3 \)) is activating and ortho/para directing. Para is major due to steric hindrance at the ortho position. While correct, it is a standard electrophilic substitution.
4. Reaction 4: Hoffmann Bromamide degradation involves the reaction of a primary amide with bromine and a base to yield a primary amine with one fewer carbon atom.
\( \text{H}_3\text{CCH}_2\text{CONH}_2 + \text{Br}_2 + 4\text{KOH} \xrightarrow{\Delta} \text{H}_3\text{CCH}_2\text{NH}_2 + 2\text{KBr} + \text{K}_2\text{CO}_3 + 2\text{H}_2\text{O} \)
Propionamide (3 carbons) gives Ethylamine (2 carbons). This is a perfectly correct and balanced major reaction.
Step 3: Final Answer:
The correct reaction is Hoffmann Bromamide degradation of propionamide to ethylamine.