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Question #44509
The Question
Consider the reaction of (1-cyclopropylethyl)benzene with anhydrous \ce{HBr} at . Assuming thermodynamic control for the intermediate rearrangement steps, identify the major organic product.
Options
- A.
3-bromo-2-phenylpentane
- B.
2-bromo-2-phenylpentane
- C.
1-bromo-2-methyl-3-phenylbutane
- D.
(1-bromo-1-cyclopropylethyl)benzene
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
Cycloalkane Ring Strain|Bond Angle Variations|Molecular Orbital Mixing
Why This Question Is Tricky
Common Mistakes
This question tests two critical exceptions and hidden variables.
First, it traps students who rely on the heuristic that 'all alkanes/cycloalkanes are inert to electrophilic addition', forcing them to recognize the unique Molecular Orbital mixing (banana bonds) of cyclopropane that allows it to react with HBr.
Second, it tests the stability of intermediates: even if a student correctly predicts the Markovnikov-like ring opening (leading to Option A), they will fail if they overlook the subsequent 1,2-hydride shift.
The shift is thermodynamically driven by the transition from a standard secondary carbocation to an exceptionally stable tertiary benzylic carbocation.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Hydrocarbons - Class 11 Part 2 |
| Concept | Cycloalkane Ring Strain |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |