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Question #44945

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following reaction sequence starting from 4-aminophenol: $\text{4-aminophenol} \xrightarrow[\text{298 K}]{\text{Ac}_2\text{O (1 eq.), H}_2\text{O, pH = 1.0}} \textbf{P}$ $\textbf{P} \xrightarrow[\text{273 K}]{\text{Ph-N}_2^+\text{Cl}^- \text{ (1 eq.), Buffer pH = 5.0}} \textbf{Q}$ Identify the major product \textbf{Q}.

Options

A.
4-amino-3-(phenyldiazenyl)phenyl acetate
B.
4-acetamido-2-(phenyldiazenyl)phenol
C.
4-acetamido-3-(phenyldiazenyl)phenol
D.
4-amino-2-(phenyldiazenyl)phenyl acetate

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Coupling Reactivity|Basicity-Solvation Competition|Amino Acid Zwitterion pH Sensitivity

Why This Question Is Tricky

Common Mistakes

This problem tests the 'pH-Dependent Protonation' exception in chemoselectivity.

The primary trap is the assumption that $-\text{NH}_2$ is always a better nucleophile than $-\text{OH}$ , leading students to incorrectly predict N-acetylation (forming paracetamol) in Step 1, which would subsequently lead to Option B.

By setting the pH to 1.0, the amine is locked as an inert ammonium ion, forcing O-acetylation.

The secondary trap evaluates the student's ability to reassess the molecule's reactivity at pH 5.0, where the amine is liberated and outcompetes the ester group to direct the azo coupling regioselectivity.

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