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Question #43972

Difficulty: 8/10 | 🟢 Free

The Question

Compound $\mathbf{X}$ is 2-(4-oxopentyl)benzaldehyde. It is heated with concentrated aqueous $\ce{KOH}$ at $353\text{ K}$ to yield a major organic product $\mathbf{Y}$ . Subsequently, $\mathbf{Y}$ is treated with $\ce{I2}$ in excess aqueous $\ce{NaOH}$ at $298\text{ K}$ , followed by careful acidification with dilute $\ce{HCl}$ , to produce compound $\mathbf{Z}$ . Identify the structure of $\mathbf{Z}$ .

Options

A.
3,4-Dihydronaphthalene-2-carboxylic acid
B.
A 1:1 mixture of 2-(3-carboxypropyl)benzoic acid and 2-(3-carboxypropyl)benzyl alcohol
C.
Naphthalene-2-carboxylic acid
D.
1H-Indene-2-carboxylic acid

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

Cannizzaro Mechanism|Reduction Selectivity (Hydrides)|Haloform Reaction Logic

Why This Question Is Tricky

Common Mistakes

The question tests the student's reliance on the 'Cannizzaro Rule of Thumb' (non-enolizable aldehydes undergo disproportionation in concentrated base).

By presenting a molecule with both an alpha-less aldehyde and a methyl ketone, the trap exploits the assumption that Cannizzaro is a fixed outcome.

In reality, the kinetic speed of the intramolecular enolate attack (Aldol condensation) completely bypasses the slow, bimolecular hydride transfer of the Cannizzaro mechanism.

Furthermore, it tests the regioselectivity of ring formation (6-membered over 8-membered) and the chemoselectivity of the Haloform reaction on an alpha,beta-unsaturated system.

Quick Facts About This Question

Question Information

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