Question

E2 elimination converts neomethyl chloride into a mixture of the following compounds:

• A. 4-menthene (75%) and 2-methene (25%)
• B. 3-menthene (25%) and 5-methene (75%)
• C. 1-menthene (50%) and 3-methene (50%)
• D. 3-menthene (75%) and 2-methene (25%)

Answer 1

The Correct Option is D

To solve this question, we need to understand the concept of E2 elimination and how it applies to neomethyl chloride. The E2 elimination reaction typically results in the formation of alkenes by removing a hydrogen and a leaving group (in this case, chloride ion) from adjacent carbon atoms, forming a double bond.

Neomethyl chloride is a quaternary ammonium compound, and under E2 reaction conditions, it can undergo dehydrohalogenation to produce alkenes. The reaction conditions favor the most substituted double bond due to the Zaitsev's rule, which states that the more substituted alkene is the major product.

Analyzing the possible products:

• The major product will likely be the most stable (i.e., the most substituted) alkene.
• The minor product will be the less stable (i.e., less substituted) alkene.

Applying this to the options provided:

1. 4-menthene (75%) and 2-methene (25%): This doesn't adhere to the stability comparison as well as the correct answer.
2. 3-menthene (25%) and 5-methene (75%): Here, 5-methene is assumed to be more stable, which is not correct compared to the third option.
3. 1-menthene (50%) and 3-methene (50%): Equal amounts suggest no preference which does not align with Zaitsev's rule.
4. 3-menthene (75%) and 2-methene (25%): Corresponds well to the Zaitsev's rule as the more substituted 3-menthene is preferred, making this the correct choice.

Conclusion: Based on Zaitsev's rule and the structure of neomethyl chloride, the elimination reaction predominantly produces 3-menthene as the major product with 75%, making it the major alkene, and 2-methene as the minor product with 25%. Thus, the correct answer is 3-menthene (75%) and 2-methene (25%).