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Question #44615
The Question
Optically pure -2-chloro-3-methylbutane is subjected to solvolysis in glacial acetic acid () at . The reaction yields a major rearranged substitution product and a minor unrearranged substitution product . Which of the following best describes the stereochemical outcome of and the primary mechanistic phenomenon responsible for it?
Options
- A.
Net inversion via an intimate (tight) ion pair shielding the front face
- B.
Complete racemization via a fully solvated, free secondary carbocation
- C.
Net retention via a solvent-separated ion pair facilitating front-side attack
- D.
Complete inversion via a concerted mechanism bypassing the carbocation
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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
SN1 Carbocation Rearrangement|SN2 Stereochemical Inversion
Why This Question Is Tricky
Common Mistakes
Students are typically taught a rigid dichotomy: leads to complete inversion, while leads to complete racemization via a 'free' carbocation.
When students see a rearranged product, they correctly identify the mechanism.
However, they falsely assume the unrearranged minor product must be completely racemic (Option B).
They overlook the Winstein ion-pair mechanism, where low-dielectric solvents stabilize an 'intimate ion pair'.
The leaving group shields the front face of the carbocation, resulting in net inversion for the pathway.
Option D is a trap for students who see inversion and incorrectly assume a competing mechanism, ignoring that weak nucleophiles like acetic acid do not favor on sterically hindered secondary substrates.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Haloalkanes and Haloarenes - Class 12 |
| Concept | SN1 Carbocation Rearrangement |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |