Which of the following are optically active?

Options

A.
B.
C.
D.

Explanation

To determine which of the given compounds are optically active, we need to follow these steps:

### Step 1: Understand the criteria for optical activity
A compound is considered optically active if:
1. It has at least one chiral carbon atom (a carbon atom that is bonded to four different groups).
2. It does not possess a plane of symmetry.

### Step 2: Analyze each compound

**Compound 1:**
- Check for chiral carbon: Identify if there is a carbon atom bonded to four different groups.
- Check for plane of symmetry: Determine if the compound can be divided into two symmetrical halves.
- **Conclusion:** This compound has a chiral carbon, but it has a plane of symmetry, so it is not optically active.

**Compound 2:**
- Check for chiral carbon: Identify if there is a carbon atom bonded to four different groups.
- Check for plane of symmetry: Determine if the compound can be divided into two symmetrical halves.
- **Conclusion:** This compound has a chiral carbon with four different substituents and does not have a plane of symmetry, making it optically active.

**Compound 3:**
- Check for chiral carbon: Identify if there is a carbon atom bonded to four different groups.
- Check for plane of symmetry: Determine if the compound can be divided into two symmetrical halves.
- **Conclusion:** This compound has groups that are not different (due to the presence of CS2 groups), and it may also have a plane of symmetry, thus it is not optically active.

### Step 3: Final determination
Based on the analysis:
- **Optically Active Compound:** Only the second compound is optically active.
- **Not Optically Active Compounds:** The first and third compounds are not optically active.

### Final Answer:
The optically active compound among the given options is the second compound.

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