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Question #44205
The Question
When 1-bromo-3,3-dimethylbicyclo[3.3.1]nonane is heated with sodium methoxide in methanol at , a single major product is formed. Identify the major product.
Options
- A.
3,3-dimethylbicyclo[3.3.1]non-1-ene
- B.
7,7-dimethylbicyclo[3.3.1]non-1-ene
- C.
3,3-dimethylbicyclo[3.3.1]non-1(9)-ene
- D.
1-methoxy-3,3-dimethylbicyclo[3.3.1]nonane
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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
Bond Angle Variations|SN1 Carbocation Rearrangement|E1/E2 Solvent and Base Effects
Why This Question Is Tricky
Common Mistakes
This question tests the limits of Bredt's Rule, Wiseman's rule for anti-Bredt alkenes, and steric control in E2 regioselectivity.
Students often memorize that 'bridgehead double bonds are impossible' and might erroneously choose the substitution product (Option D).
However, Wiseman's rule states that anti-Bredt alkenes can form if the trans-double bond is in an 8-membered or larger ring.
The strong base forces an E2 pathway.
Elimination at C9 forms a highly strained trans-cyclohexene, while elimination at C2 or C8 forms a stable trans-cyclooctene derivative.
The key trap is regioselectivity: students must recognize the severe neopentyl-like steric hindrance at C2 caused by the 3,3-dimethyl group, which directs the base to abstract the proton at C8.
Finally, the numbering shift from 3,3-dimethyl to 7,7-dimethyl rigorously tests IUPAC nomenclature mastery.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Bonding and Molecular Structure - Class 11 Part 1 |
| Concept | Bond Angle Variations |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |