Question

X and Y (major products) in the following reaction sequence are

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Hint:

Understand the role of protecting groups in electrophilic aromatic substitution. Acetylation of aniline converts the strongly activating \( -NH_2 \) group to the moderately activating and ortho/para-directing \( -NHCOCH_3 \) group, allowing for better control of subsequent substitution reactions. Consider the directing effects and steric hindrance when predicting the major product of electrophilic aromatic substitution on substituted benzene rings.

Answer 1

The Correct Option is D

The reaction sequence starts with aniline reacting with acetic anhydride in the presence of pyridine.
Acetic anhydride is an acetylating agent, and pyridine acts as a base to facilitate the reaction by removing the \( H^+ \) byproduct.
This reaction will acetylate the amino group (\( -NH_2 \)) of aniline to form an amide (\( -NHCOCH_3 \)), which is acetanilide.
The amino group is a strong activating and ortho/para-directing group in electrophilic aromatic substitution.
By converting it to an amide, we make it moderately activating and still ortho/para-directing, but less so.
This step is done to control the subsequent bromination.
Thus, X is acetanilide.
The structure of X (acetanilide) is: In the second step, acetanilide reacts with \( Br_2 \) in acetic acid (\( CH_3COOH \)).
Bromine is an electrophile, and acetanilide will undergo electrophilic aromatic substitution.
The amide group (\( -NHCOCH_3 \)) is an ortho/para-directing group.
However, due to steric hindrance at the ortho positions (adjacent to the bulky amide group) and the slightly higher activation of the para position, the major product will be the para-substituted bromoacetanilide.
The structure of Y (para-bromoacetanilide) is: Comparing these structures with the options, option (D) correctly shows X as acetanilide and Y as para-bromoacetanilide.