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Question #44442

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The Question

Compound $\mathbf{X}$ is 5,5-dimethylcyclohexane-1,3-dione. Oxidation of $\mathbf{X}$ with \ce{SeO2} yields a vicinal tricarbonyl compound $\mathbf{Y}$ . In aqueous medium, $\mathbf{Y}$ exists almost exclusively as a stable gem-diol $\mathbf{Z}$ due to strong intramolecular dipole repulsion. Complete oxidative cleavage of 1 mole of $\mathbf{Z}$ with an excess of periodic acid (\ce{HIO4}) at 298 K yields 1 mole of a dicarboxylic acid $\mathbf{W}$ and 1 mole of a gas $\mathbf{G}$ .

Identify $\mathbf{W}$ , $\mathbf{G}$ , and the total number of moles of \ce{HIO4} consumed per mole of $\mathbf{Z}$ .

Options

A.
\textbf{W} = 3,3-dimethylpentanedioic acid; \textbf{G} = \ce{CO2}; Moles of \ce{HIO4} = 2
B.
\textbf{W} = 2,2-dimethylpentanedioic acid; \textbf{G} = \ce{CO2}; Moles of \ce{HIO4} = 2
C.
\textbf{W} = 3,3-dimethylpentanedioic acid; \textbf{G} = \ce{CO}; Moles of \ce{HIO4} = 1
D.
\textbf{W} = 3,3-dimethylhexanedioic acid; \textbf{G} = \ce{CO2}; Moles of \ce{HIO4} = 3

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

Hydrate Stability vs. Carbonyl|Glycol Periodic Acid Cleavage

Why This Question Is Tricky

Common Mistakes

This problem tests the student's ability to recognize that while isolated ketones do not react with \ce{HIO4}, vicinal tricarbonyls exist as hydrates (gem-diols) in aqueous media.

This hidden intermediate acts as an $\alpha$ -hydroxy ketone equivalent, triggering a cascade of oxidative cleavages.

A common trap is failing to recognize the second cleavage of the resulting $\alpha$ -keto acid, which leads to the extrusion of \ce{CO2} and the consumption of a second equivalent of \ce{HIO4}.

Distractors exploit incorrect regioselectivity of \ce{SeO2} oxidation or incomplete cleavage.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Aldehydes, Ketones, and Carboxylic Acids - Class 12
Concept	Hydrate Stability vs. Carbonyl
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free