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Question #45055
The Question
Consider the reaction of (2R, 3S)-2-bromo-2,3-diphenylbutane with potassium \textit{tert}-butoxide () in \textit{tert}-butanol () at . Identify the major product formed, taking into account both regioselectivity and stereochemistry.
Options
- A.
(3S)-2,3-diphenyl-1-butene
- B.
(3R)-2,3-diphenyl-1-butene
- C.
(2E)-2,3-diphenyl-2-butene
- D.
(2Z)-2,3-diphenyl-2-butene
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
Resonance Energy and Stability|E2 Regioselectivity (Saytzeff vs Hoffmann)|Cahn-Ingold-Prelog (CIP) Priority
Why This Question Is Tricky
Common Mistakes
This question tests the boundary between thermodynamic and kinetic control in E2 eliminations.
Students often fall into the trap of assuming that a highly resonance-stabilized (conjugated) alkene will always be the major product (Saytzeff rule).
Here, the extreme steric bulk of both the base and the substrate's transition state forces an unconventional Hoffmann elimination.
Furthermore, it tests a deep understanding of CIP priority rules; students frequently misassign the priority of the newly formed -C(Ph)=CH2 group relative to a -Ph group, or incorrectly assume that a reaction at an adjacent carbon inherently flips the stereochemical designation.
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 |