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Question #43956

Difficulty: 8/10 | 🟢 Free

The Question

An organic compound $\mathbf{X}$ ( $\ce{C11H12O2}$ ) is identified as 2,2-dimethyl-3-oxo-3-phenylpropanal.

Reaction I: $\mathbf{X}$ is treated with an excess of $\ce{LiAlH4}$ in anhydrous ether, followed by mild acidic workup, to yield the major product $\mathbf{Y}$ .

Reaction II: $\mathbf{X}$ is heated with concentrated aqueous $\ce{NaOH}$ , followed by acidic workup, to yield a major organic product $\mathbf{Z}$ containing a benzene ring, along with a one-carbon byproduct.

Identify $\mathbf{Y}$ and $\mathbf{Z}$ .

Options

A.
$\mathbf{Y}$ : 2,2-dimethyl-1-phenylpropane-1,3-diol; $\mathbf{Z}$ : 2-methyl-1-phenylpropan-1-one
B.
$\mathbf{Y}$ : 2,2-dimethyl-1-phenylpropane-1,3-diol; $\mathbf{Z}$ : 3-hydroxy-2,2-dimethyl-3-phenylpropanoic acid
C.
$\mathbf{Y}$ : 2,2-dimethyl-1-phenylpropane-1,3-diol; $\mathbf{Z}$ : 2,2-dimethyl-3-oxo-3-phenylpropanoic acid
D.
$\mathbf{Y}$ : 3-hydroxy-2,2-dimethyl-3-phenylpropanal; $\mathbf{Z}$ : 3-hydroxy-2,2-dimethyl-3-phenylpropanoic acid

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

Reduction Selectivity (Hydrides)|Alpha-Hydrogen Acidity|Cannizzaro Mechanism

Why This Question Is Tricky

Common Mistakes

The question tests the kinetic competition between hydride transfer (Cannizzaro reaction) and enolate expulsion (retro-Claisen cleavage).

Students often blindly apply the heuristic 'no alpha-hydrogens + strong base = Cannizzaro', leading them to incorrectly predict an intramolecular Cannizzaro product (Option B).

The hidden variable is the leaving group ability: an enolate is a significantly better leaving group than a hydride ion, making C-C bond cleavage (deformylation) the dominant pathway for alpha,alpha-disubstituted beta-keto aldehydes.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Aldehydes, Ketones, and Carboxylic Acids - Class 12
Concept	Reduction Selectivity (Hydrides)
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free