Which of the following compounds is not chiral?

Options

A. 1-Chloropentane
B. 2- Chloropentane
C. 1-Chloro-2-methyl pentane
D. 3-Chloro-2-methyl pentane.

Explanation

To determine which of the given compounds is not chiral, we need to analyze each compound based on the presence of a chiral center. A chiral center is typically a carbon atom that is bonded to four different groups. If a carbon atom has two or more identical groups, it is not chiral.

Let's analyze the options step by step:

### Step 1: Analyze 1-Chloropentane
1. **Structure**: The molecular structure of 1-chloropentane can be represented as follows:
- CH3-CH2-CH2-CH2-Cl
2. **Chiral Center Check**: The carbon atom at position 1 (the one bonded to chlorine) is bonded to:
- Chlorine (Cl)
- Three hydrogen atoms (H)
- Therefore, this carbon has two identical hydrogen atoms.
3. **Conclusion**: Since there are two identical groups (hydrogens), 1-chloropentane is **not chiral**.

### Step 2: Analyze 2-Chloropentane
1. **Structure**: The molecular structure of 2-chloropentane can be represented as follows:
- CH3-CH(Cl)-CH2-CH2-CH3
2. **Chiral Center Check**: The carbon atom at position 2 (the one bonded to chlorine) is bonded to:
- Chlorine (Cl)
- Methyl group (CH3)
- Ethyl group (CH2-CH3)
- Hydrogen (H)
3. **Conclusion**: All four groups are different, so 2-chloropentane is **chiral**.

### Step 3: Analyze 1-Chloro-2-methylpentane
1. **Structure**: The molecular structure of 1-chloro-2-methylpentane can be represented as follows:
- CH3-CH(Cl)-CH(CH3)-CH2-CH3
2. **Chiral Center Check**: The carbon atom at position 2 (the one bonded to chlorine and methyl) is bonded to:
- Chlorine (Cl)
- Methyl group (CH3)
- Ethyl group (CH2-CH3)
- Hydrogen (H)
3. **Conclusion**: All four groups are different, so 1-chloro-2-methylpentane is **chiral**.

### Step 4: Analyze 3-Chloro-2-methylpentane
1. **Structure**: The molecular structure of 3-chloro-2-methylpentane can be represented as follows:
- CH3-CH(Cl)-CH(CH3)-CH2-CH3
2. **Chiral Center Check**: The carbon atom at position 3 (the one bonded to chlorine and methyl) is bonded to:
- Chlorine (Cl)
- Methyl group (CH3)
- Ethyl group (CH2-CH3)
- Hydrogen (H)
3. **Conclusion**: All four groups are different, so 3-chloro-2-methylpentane is **chiral**.

### Final Conclusion
Based on the analysis:
- The only compound that is **not chiral** is **1-chloropentane**.

### Answer: 1-Chloropentane

---