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Question #45086
The Question
Consider the following reaction sequence:
Which of the following correctly identifies the products \textbf{R} and \textbf{S}?
Options
- A.
4,4-dimethylpentan-2-one and formaldehyde
- B.
Propan-2-one and 2,2-dimethylpropanal
- C.
3,3-dimethylbutan-2-one and acetaldehyde
- D.
2,2-dimethylpropanal and acetaldehyde
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
Reaction Intermediates Stability|Steric Hindrance (B-Strain)|Williamson Ether Synthesis Constraints
Why This Question Is Tricky
Common Mistakes
This question tests the student's ability to recognize when steric effects (B-strain) override standard empirical rules (Zaitsev's rule) in elimination reactions.
Students typically memorize that small bases like ethoxide () favor the more substituted Zaitsev alkene.
However, in highly branched systems like 2-bromo-2,4,4-trimethylpentane, the transition state leading to the Zaitsev product suffers from severe steric hindrance (B-strain) between the bulky \textit{tert}-butyl group and the base/leaving group.
Consequently, the reaction is kinetically controlled to proceed via the less hindered pathway, yielding the Hofmann alkene (2,4,4-trimethyl-1-pentene) as the major product.
The trap lies in blindly applying Zaitsev's rule without analyzing the 3D steric environment of the transition state.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Reaction Intermediates Stability |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |