Which of the following reactions give meso product?

Options

A.
B.
C.
D.

Explanation

To determine which of the given reactions yield meso products, we need to understand what a meso compound is. A meso compound is a molecule that contains chiral centers but is optically inactive due to an internal plane of symmetry.

### Step-by-Step Solution:

1. **Identify Meso Compounds**:
- A meso compound has chiral centers but is achiral due to symmetry. This means that even though it has chiral centers, it does not rotate plane-polarized light.

2. **Analyze Option A**:
- Reaction: CH3C≡CCH3 + Br2 (in CCl4)
- The reaction involves anti-addition of bromine across the double bond. The product will have a center of symmetry, making it a meso compound.
- **Conclusion**: Option A gives a meso product.

3. **Analyze Option B**:
- Reaction: CH3C≡CCH3 + H2O (using B2H6)
- This reaction involves syn-addition of OH groups to the double bond. The resulting product will also have a plane of symmetry.
- **Conclusion**: Option B gives a meso product.

4. **Analyze Option C**:
- Reaction: CH3C≡CCH3 + H2O (using B2H6)
- Similar to option B, but the product does not have a plane of symmetry due to the arrangement of substituents.
- **Conclusion**: Option C does not give a meso product.

5. **Analyze Option D**:
- Reaction: Cyclohexene + Br2 (in CCl4)
- The product will have two chiral centers but lacks an internal plane of symmetry, making it optically active.
- **Conclusion**: Option D does not give a meso product.

### Final Answer:
The reactions that give meso products are **Option A and Option B**.