In which of the following reactions the correct major products are mentioned

Options

A.
B.
C.
D.

Answer

To determine the correct major products in the given reactions, we will analyze each reaction step by step, focusing on the E2 elimination mechanism, which requires an anti-periplanar arrangement of the leaving group and the hydrogen atom being removed.

### Step-by-Step Solution:

1. **Identify the Reactions**: We have four reactions to analyze. Each involves an E2 elimination mechanism.

2. **Understand E2 Mechanism**:
- E2 elimination requires the leaving group and the hydrogen atom being eliminated to be in an anti-periplanar arrangement. This means they should be on opposite sides of the molecule.

3. **Analyze the First Reaction**:
- **Reaction**: 2-methyl-hydrocyclohexane → cyclohexene
- **Structure**: Iodine (I) is in a wedge position, and the methyl (CH3) is in a dash position.
- **Analysis**: The hydrogen atom that would be eliminated is not in an anti-periplanar position with the iodine. Therefore, the major product cannot be formed as suggested.
- **Conclusion**: This reaction is incorrect.

4. **Analyze the Second Reaction**:
- **Reaction**: CD3 and CH3 groups present.
- **Structure**: The hydrogen from the CH3 group is in a wedge position.
- **Analysis**: The hydrogen atom is anti-periplanar to the leaving group (Br). Thus, the elimination can occur, leading to the correct product.
- **Conclusion**: This reaction is correct.

5. **Analyze the Third Reaction**:
- **Reaction**: CH3 and OTS (a leaving group).
- **Structure**: The hydrogen is in a dash position, and OTS is positioned such that they are not anti-periplanar.
- **Analysis**: The hydrogen and OTS are not anti-periplanar, so the elimination cannot occur as suggested.
- **Conclusion**: This reaction is incorrect.

6. **Analyze the Fourth Reaction**:
- **Reaction**: OH group in a wedge position.
- **Structure**: The hydrogen is in a dash position.
- **Analysis**: The hydrogen can be eliminated as it is anti-periplanar to the OH group. However, the product shown is incorrect as it does not reflect the correct double bond formation.
- **Conclusion**: This reaction is incorrect.

### Final Conclusion:
- The correct major products are only from the **Second Reaction**.
- The **First**, **Third**, and **Fourth Reactions** are incorrect.

### Summary of Correctness:
- **1st Reaction**: Incorrect
- **2nd Reaction**: Correct
- **3rd Reaction**: Incorrect
- **4th Reaction**: Incorrect