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Question #45056
The Question
Consider the organic compound \textbf{P}, 3-(2-ethoxy-2-oxoethyl)-5,5-dimethylcyclohex-2-en-1-one. \textbf{P} is subjected to the following reaction sequence:
Step 1: \ce{Li} (2.0 eq.), liquid \ce{NH3}, \ce{t-BuOH} (1.0 eq.), ; then evaporate \ce{NH3} and replace solvent with \ce{Et2O}. Step 2: \ce{CH3MgBr} (excess), warm to . Step 3: \ce{H3O+} (aqueous workup).
Identify the major product \textbf{Q} formed at the end of the sequence.
Options
- A.
3-(2-hydroxy-2-methylpropyl)-5,5-dimethylcyclohexan-1-one
- B.
3-(2-hydroxy-2-methylpropyl)-1,5,5-trimethylcyclohexan-1-ol
- C.
3-(2-ethoxy-2-oxoethyl)-1,5,5-trimethylcyclohex-2-en-1-ol
- D.
3-(2-ethoxy-2-oxoethyl)-1,5,5-trimethylcyclohexan-1-ol
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
Resonance Energy and Stability|Reduction Selectivity (Sn/HCl vs LiAlH4)|Grignard Reagent Sensitivity
Why This Question Is Tricky
Common Mistakes
This problem tests the concept of 'in-situ protection' and the kinetic control of chemoselectivity.
Normally, ketones are significantly more electrophilic than esters and react faster with Grignard reagents.
Students often fall into the trap of assuming the Grignard reagent will attack the ketone (leading to Option B or D).
However, the hidden variable here is the intermediate generated by the dissolving metal reduction: a stable lithium enolate.
This enolate acts as an internal protecting group, reversing the inherent electrophilicity trends by rendering the ketone inert.
The Grignard reagent is forced to selectively attack the latent ester group.
This highlights the importance of tracking the exact state of intermediates before workup.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Resonance Energy and Stability |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |