Which of the following be optically active ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given compounds is optically active, we need to identify if they possess a chiral carbon atom. A chiral carbon atom is one that is bonded to four different groups. Let's analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Requirement for Optical Activity**:
- A compound is optically active if it has at least one chiral carbon atom.

2. **Analyze Option 1**:
- In the first compound, we examine a carbon atom that is bonded to:
- A methyl group (−CH₃)
- An ethyl group (−C₂H₅)
- A propyl group (−C₃H₇)
- A hydroxyl group (−OH)
- Since all four groups attached to this carbon are different, this carbon is a chiral center.
- **Conclusion**: This compound is optically active.

3. **Analyze Option 2**:
- In the second compound, we find a carbon atom bonded to:
- Two methyl groups (−CH₃)
- An ethyl group (−C₂H₅)
- Here, two of the groups are identical (the two methyl groups), meaning this carbon does not have four different groups.
- **Conclusion**: This compound is not optically active.

4. **Analyze Option 3**:
- In the third compound, we look at a carbon atom that is bonded to:
- Two hydrogen atoms (−H)
- Another group (not specified)
- Since two of the groups are identical (the two hydrogen atoms), this carbon does not have four different groups.
- **Conclusion**: This compound is not optically active.

5. **Analyze Option 4**:
- In the fourth compound, we check a carbon atom that is bonded to:
- An isopropyl group (−C₃H₇)
- A hydroxyl group (−OH)
- Two hydrogen atoms (−H)
- Again, since two of the groups are identical (the two hydrogen atoms), this carbon does not have four different groups.
- **Conclusion**: This compound is not optically active.

### Final Answer:
- The only optically active compound is from **Option 1**, which has a chiral carbon center.