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Question #43989

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following reaction sequence: $\ce{Phenol ->[\text{1. } CO_2, NaOH, 400 \text{ K, 4-7 atm}][\text{2. } H_3O^+] P ->[CH_3OH][H^+ \text{ (cat.)}] Q ->[NH_3 \text{ (aq)}] R ->[Br_2, KOH \text{ (aq)}][\Delta] S \text{ (Major Product)}}$ Identify the major organic product S.

Options

A.
2-Aminophenol
B.
1,3-Benzoxazol-2(3H)-one
C.
4-Aminophenol
D.
3,5-Dibromo-2-hydroxybenzamide

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

Carboxylic Acid Strength|Hoffmann Bromamide Rearrangement|Nucleophilic Acyl Substitution

Why This Question Is Tricky

Common Mistakes

The problem tests the regioselectivity of the Kolbe-Schmitt reaction and a critical exception in the Hoffmann Bromamide Rearrangement (HBR).

While HBR typically converts primary amides to primary amines, an ortho-substituent capable of acting as a nucleophile (like a phenoxide ion in basic medium) intercepts the isocyanate intermediate.

Instead of undergoing hydration and decarboxylation to form 2-aminophenol, the isocyanate undergoes rapid intramolecular nucleophilic attack by the phenoxide oxygen.

This Neighboring Group Participation (NGP) forms a stable cyclic carbamate (1,3-benzoxazol-2(3H)-one).

Students failing to account for this intramolecular trapping will incorrectly predict 2-aminophenol.

Furthermore, the use of NaOH in the first step specifically directs ortho-substitution, whereas KOH would have favored the para-isomer, leading to 4-aminophenol.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Aldehydes, Ketones, and Carboxylic Acids - Class 12
Concept	Carboxylic Acid Strength
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free