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Question #44610
The Question
An equimolar mixture of bromocyclohexane and 3,3-dimethylbut-1-yne is dissolved in dry THF. To this solution, 1.0 equivalent of magnesium turnings is added, and the mixture is stirred at until the magnesium is completely consumed. Subsequently, 1.0 equivalent of acetaldehyde () is added to the reaction mixture, followed by a standard acidic workup (). Identify the major organic product isolated from this sequence.
Options
- A.
5,5-Dimethylhex-3-yn-2-ol
- B.
1-Cyclohexylethan-1-ol
- C.
1-Cyclohexyl-3,3-dimethylbut-1-yne
- D.
4,4-Dimethylpent-2-yn-1-ol
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
C-X Bond Polarization and Polarizability|Grignard Reaction Pathways|Grignard Reagent Sensitivity
Why This Question Is Tricky
Common Mistakes
The hidden variable being tested is the strict hierarchy of Grignard reagent reactivity.
Students often memorize the 'Umpolung' concept (polarization inversion) where Grignard reagents act as nucleophiles toward carbonyls.
However, they overlook the extreme sensitivity of organometallics to protic sources.
Here, the terminal alkyne acts as an internal 'protic trap'.
The chemical exception is that the thermodynamics of the acid-base reaction (forming a much weaker conjugate base) is diffusion-controlled and completely outcompetes the intended nucleophilic addition pathway of the original alkyl Grignard, fundamentally altering the terminal fate of the reagent.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Haloalkanes and Haloarenes - Class 12 |
| Concept | C-X Bond Polarization and Polarizability |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |