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Question #44409
The Question
Consider the specific stereoisomer of 2-amino-5-(tert-butyl)-1-phenylcyclohexan-1-ol where, in its most stable chair conformation, the \textit{tert}-butyl, phenyl, and amino groups are all equatorial, and the hydroxyl group is axial. This compound is treated with \ce{NaNO2} and aqueous \ce{HCl} at . Identify the major organic product formed.
Options
- A.
(3-(tert-butyl)cyclopentyl)(phenyl)methanone
- B.
5-(tert-butyl)-2-phenylcyclohexan-1-one
- C.
4-(tert-butyl)-2-phenylcyclohexan-1-one
- D.
5-(tert-butyl)-1-phenylcyclohex-1-ene
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
Pinacol-Pinacolone Rearrangement|Optical Isomerism Logic
Why This Question Is Tricky
Common Mistakes
This question tests the supremacy of Stereoelectronic Control over inherent Migratory Aptitude in rigid cyclic systems.
A common trap for students is to blindly apply the rule that 'Phenyl has a higher migratory aptitude than alkyl groups' and incorrectly predict phenyl migration (which would yield 5-(tert-butyl)-2-phenylcyclohexan-1-one).
However, in the semi-pinacol rearrangement, the transition state requires the migrating group to be anti-periplanar to the leaving group.
Because the diazonium leaving group is equatorial, the anti-periplanar group is the adjacent C-C ring bond, forcing a ring contraction regardless of the phenyl group's higher electronic migratory aptitude.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Alcohols, Phenols, and Ethers - Class 12 |
| Concept | Pinacol-Pinacolone Rearrangement |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |