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Question #44938

Difficulty: 8/10 | 🟢 Free

The Question

Compound \textbf{A} (3,5-dimethylaniline) is treated with 1 equivalent of benzenediazonium chloride at $0-5^\circ \text{C}$ in a weakly acidic medium (pH 4-5). It undergoes exclusive C-coupling to yield compound \textbf{B} as the major product. Compound \textbf{B} is then subjected to exhaustive reductive cleavage using $\ce{SnCl2 / HCl}$ , followed by neutralization, to yield aniline and compound \textbf{C}.

What is the number of distinct signals observed in the proton-decoupled $^{13}\text{C}$ NMR spectrum of compound \textbf{C}?

Options

A.
8
B.
5
C.
6
D.
4

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Ortho-Effect in Anilines|Azo Coupling Regioselectivity|Electrophilic Substitution Control

Why This Question Is Tricky

Common Mistakes

This question tests a critical exception to the general rule of Electrophilic Aromatic Substitution in azo coupling.

Students are taught that bulky diazonium ions exclusively attack the para position of anilines to avoid steric hindrance from the ortho position.

However, in 3,5-dimethylaniline, the para position is flanked by two methyl groups, making it significantly more sterically hindered than the ortho position (which is flanked by one methyl and one smaller amino group).

Failing to account for this specific steric environment leads students to incorrectly predict para-coupling, resulting in a symmetric product (1,4-diamino-3,5-dimethylbenzene) and an incorrect $^{13}\text{C}$ NMR signal count of 5.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Ortho-Effect in Anilines
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free