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Question #44443

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The Question

Compound $\textbf{X}$ (1,1,1,3,3,3-hexafluoropropane-2,2-diol) is the stable crystalline hydrate of hexafluoroacetone. When 1.0 mole of $\textbf{X}$ is treated with an excess of methylmagnesium bromide (\ce{CH3MgBr}) in anhydrous diethyl ether at 298 K, a gas $\textbf{G}$ is evolved. The reaction mixture is subsequently subjected to mild aqueous acidic workup to yield the major organic product $\textbf{Y}$ . Identify the total moles of gas $\textbf{G}$ evolved during the Grignard reaction per mole of $\textbf{X}$ , and the identity of product $\textbf{Y}$ .

Options

A.
2 moles of \ce{CH4}; $\textbf{Y}$ is 1,1,1,3,3,3-hexafluoropropane-2,2-diol
B.
1 mole of \ce{CH4}; $\textbf{Y}$ is 1,1,1,3,3,3-hexafluoro-2-methylpropan-2-ol
C.
2 moles of \ce{CH4}; $\textbf{Y}$ is 1,1,1,3,3,3-hexafluoro-2-methylpropan-2-ol
D.
0 moles of \ce{CH4}; $\textbf{Y}$ is 1,1,1,3,3,3-hexafluoro-2,2-dimethylpropane

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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

Hydrate Stability vs. Carbonyl|Grignard Reaction Pathways

Why This Question Is Tricky

Common Mistakes

This question tests the kinetic vs thermodynamic control and the dual nature of Grignard reagents.

Students often fall into the trap of assuming the hydrate is merely a source of water and ketone, predicting that water consumes 1 eq of Grignard (yielding 1 mole CH4) and the ketone undergoes nucleophilic addition to form a tertiary alcohol (Option B).

However, they fail to recognize that the stable gem-diol itself acts as a di-acid.

The kinetically favored acid-base reaction completely outcompetes any equilibrium-driven nucleophilic attack, trapping the molecule as an unreactive dianion until workup restores the original compound.

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