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Question #44946

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following two reaction sequences involving aniline:

\textbf{Sequence 1:} $\ce{C6H5NH2 ->[(CH3CO)2O][\text{Pyridine}] \textbf{P} ->[Ph-N2+Cl^-][\text{pH } 4-5,\ 0-5^\circ C] \textbf{Q}}$

\textbf{Sequence 2:} $\ce{C6H5NH2 ->[Ph-N2+Cl^-][\text{pH } 4-5,\ 0-5^\circ C] \textbf{R} ->[H^+,\ \Delta] \textbf{S} \text{ (Major product)}}$

Identify the products $\textbf{Q}$ and $\textbf{S}$ .

Options

A.
$\textbf{Q}$ = 4-phenylazoacetanilide ; $\textbf{S}$ = 4-aminoazobenzene
B.
$\textbf{Q}$ = No coupling reaction ( $\textbf{P}$ is recovered) ; $\textbf{S}$ = 4-aminoazobenzene
C.
$\textbf{Q}$ = No coupling reaction ( $\textbf{P}$ is recovered) ; $\textbf{S}$ = 1,3-diphenyltriazene
D.
$\textbf{Q}$ = 4-phenylazoacetanilide ; $\textbf{S}$ = 1,3-diphenyltriazene

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

Coupling Reactivity|Aniline Resonance Pitfalls|Electrophilic Substitution Control

Why This Question Is Tricky

Common Mistakes

This question tests a critical 'Chemical Exception' regarding the reactivity threshold in Electrophilic Aromatic Substitution (EAS).

Students often blindly categorize the $\ce{-NHCOCH3}$ group as 'activating' and assume it will undergo all typical EAS reactions like free aniline.

However, diazonium coupling requires an exceptionally high electron density on the ring.

The amide resonance in acetanilide diverts the nitrogen lone pair away from the benzene ring, suppressing its nucleophilicity below the required threshold for coupling with weak diazonium electrophiles.

Additionally, it tests the kinetic N-coupling of primary amines followed by thermodynamic rearrangement to C-coupling.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Amines - Class 12
Concept	Coupling Reactivity
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free