Question

Aniline reacts with acetic anhydride in pyridine to give a product which reacts with Br2 in CH3COOH to get

• A. o-bromoaniline
• B. p-bromoaniline
• C. p-bromoacetanilide
• D. o-bromoacetanilide
• E. m-bromoacetanilide

Hint:

Protection of aniline with acetic anhydride is a standard lab procedure to avoid multi-substitution and to direct the incoming group to the para position.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Aniline is highly reactive towards electrophilic substitution. Directly brominating aniline often results in trisubstitution (\(2,4,6\)-tribromoaniline).
To get a monosubstituted product, the amino group must be protected/deactivated.

Step 3: Detailed Explanation:
1. Acetylation: Aniline reacts with acetic anhydride in pyridine to form acetanilide. This "protects" the \(-NH_2\) group by converting it to the \(-NHCOCH_3\) group, which is less activating due to resonance with the carbonyl group.
2. Bromination: When acetanilide is treated with \(Br_2\) in acetic acid, electrophilic substitution occurs. The acetamido group is ortho-para directing.
3. Due to the steric hindrance of the bulky acetamido group, the para-product is formed as the major product.
The final product is p-bromoacetanilide.

Step 4: Final Answer:
The product obtained is p-bromoacetanilide.