Which of the following compounds is not chiral ?

Options

A. 1-chloropentane
B. 2-chloropenatne
C. 1-chloro-2-methylpentane
D. 3-chloro-2-methylpentane

Explanation

To determine which of the given compounds is not chiral, we need to identify the presence of chiral centers in each compound. A chiral center is typically an sp3 hybridized carbon atom that is bonded to four different groups. If a compound has a chiral center, it is considered chiral; if it does not, it is achiral.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to analyze:
- 1-chloropentane
- 2-chloropentane
- 1-chloro-2-methylpentane
- 3-chloro-2-methylpentane

2. **Draw the Structures**:
- **1-chloropentane**: This compound has a straight-chain structure with chlorine attached to the first carbon.
- **2-chloropentane**: Here, chlorine is attached to the second carbon of the pentane chain.
- **1-chloro-2-methylpentane**: This structure has a chlorine atom on the first carbon and a methyl group on the second carbon.
- **3-chloro-2-methylpentane**: In this case, chlorine is on the third carbon and a methyl group on the second carbon.

3. **Analyze Each Compound for Chiral Centers**:
- **1-chloropentane**: The first carbon has two hydrogens attached, making it not a chiral center. Therefore, 1-chloropentane is achiral.
- **2-chloropentane**: The second carbon has four different groups (Cl, CH2, CH3, and H), making it a chiral center. Thus, it is chiral.
- **1-chloro-2-methylpentane**: The carbon with the chlorine and methyl groups also has four different groups attached, making it chiral.
- **3-chloro-2-methylpentane**: Similar to the previous case, the carbon with chlorine and methyl groups is also chiral.

4. **Conclusion**: Among the four compounds, only **1-chloropentane** does not have a chiral center and is therefore not chiral. The other three compounds are chiral.

### Final Answer:
The compound that is not chiral is **1-chloropentane**.