Out of the following the alkene that exhibits optical isomerism is

Options

A. 3-methyl-2-pentene
B. 4-methyl-1-pentene
C. 3-methyl-1-pentene
D. 2-methyl-2-pentene

Answer

To determine which alkene exhibits optical isomerism, we need to identify if any of the given alkenes contain a chiral carbon. A chiral carbon is defined as a carbon atom that is bonded to four different substituents.

### Step-by-Step Solution:

1. **Identify the Alkenes**: The question provides four alkenes. We will analyze each one to see if it has a chiral carbon.
- **Alkene 1**: 3-methyl-2-pentene
- **Alkene 2**: 4-methyl-1-pentene
- **Alkene 3**: 3-methyl-1-pentene
- **Alkene 4**: 2-pentene

2. **Draw the Structures**: We will draw the structures of each alkene to visualize the arrangement of atoms.
- **3-methyl-2-pentene**:
```
CH3-CH=C(CH3)-CH2-CH3
```
- **4-methyl-1-pentene**:
```
CH2=CH-CH2-CH(CH3)-CH3
```
- **3-methyl-1-pentene**:
```
CH2=CH-CH(CH3)-CH2-CH3
```
- **2-pentene**:
```
CH3-CH=CH-CH2-CH3
```

3. **Analyze Each Structure for Chirality**:
- **Alkene 1 (3-methyl-2-pentene)**: The carbon with the double bond (C2) cannot be chiral as it is bonded to two identical methyl groups. No chiral carbon.
- **Alkene 2 (4-methyl-1-pentene)**: The carbon with the double bond (C1) is also not chiral as it is bonded to two hydrogen atoms. No chiral carbon.
- **Alkene 3 (3-methyl-1-pentene)**: The carbon at position 3 is bonded to:
- Ethyl group (C2H5)
- Methyl group (CH3)
- Hydrogen (H)
- The rest of the carbon chain (C1)
This carbon is a chiral center because all four substituents are different. Thus, this alkene can exhibit optical isomerism.
- **Alkene 4 (2-pentene)**: The carbon with the double bond (C2) is not chiral as it is bonded to two identical groups. No chiral carbon.

4. **Conclusion**: Only **3-methyl-1-pentene** has a chiral carbon and can exhibit optical isomerism.

### Final Answer:
The alkene that exhibits optical isomerism is **3-methyl-1-pentene**.