Which of the following molecules are chiral?

Options

A.
B.
C.
D.

Explanation

To determine which of the given molecules are chiral, we need to analyze each option based on the criteria for chirality. A molecule is considered chiral if it cannot be superimposed on its mirror image, which typically means it lacks a plane of symmetry and a center of symmetry.

### Step-by-Step Solution:

1. **Analyze Option A:**
- Check for symmetry: Option A has both a plane of symmetry and a center of symmetry.
- Conclusion: Since it has symmetry, **Option A is achiral**.

2. **Analyze Option B:**
- Check for symmetry: Option B does not have a plane of symmetry or a center of symmetry.
- Check for chirality: The carbon atom in Option B is bonded to four different groups (OH, CH3, and two other distinct groups).
- Conclusion: Since it lacks symmetry and has four different substituents, **Option B is chiral**.

3. **Analyze Option C:**
- Check for symmetry: Option C has a plane of symmetry.
- Conclusion: Because it has symmetry, **Option C is achiral**.

4. **Analyze Option D:**
- Check for symmetry: Option D does not have a plane of symmetry or a center of symmetry.
- Check for chirality: Similar to Option B, it has a carbon atom bonded to four different groups.
- Conclusion: Since it lacks symmetry and has four different substituents, **Option D is chiral**.

### Final Conclusion:
- **Chiral Molecules:** B and D
- **Achiral Molecules:** A and C