Question

Aniline on direct nitration yields

• A. 51%-ortho, 47%-para, 2%-meta derivatives
• B. 51%-meta, 47%-ortho, 2%-para derivatives
• C. 51%-para, 47%-meta, 2%-ortho derivatives
• D. 51%-ortho, 47%-meta, 2%-para derivatives

Hint:

To get purely para-nitroaniline, protect the \( -NH_2 \) group by acetylation (\( -NHCOCH_3 \)) first, then nitrate and hydrolyze.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Aniline is ortho-para directing due to the \( +M \) effect. However, nitration is done in a strongly acidic medium (\( HNO_3 + H_2SO_4 \)).
Step 2: Detailed Explanation:
In the acidic nitrating mixture, aniline gets protonated to form the anilinium ion (\( -NH_3^+ \)).
The anilinium ion is strongly electron-withdrawing (\( -I \) effect) and is meta-directing.
As a result, a substantial amount (47%) of the meta-nitroaniline is formed.
The non-protonated aniline still undergoes para-substitution (51%) and ortho-substitution (2%).
Step 3: Final Answer:
The yield is 51% para, 47% meta, and 2% ortho.