Which compounds is achiral in the following?

Options

A. 1- chloro-2- methyl pentane
B. 2- chloropentane
C. 1- chloropentane
D. 3- chloro- 2-methyl pentane

Answer

To determine which compound is achiral among the given options, we need to identify whether each compound has a chiral carbon center. A chiral carbon center is a carbon atom that is bonded to four different groups. If a compound does not have any chiral carbon centers, it is considered achiral.

### Step-by-Step Solution:

1. **Understand the Definition of Chirality**:
- A compound is chiral if it has at least one chiral carbon center (a carbon atom bonded to four different groups).
- A compound is achiral if it does not have any chiral carbon centers.

2. **Analyze Each Compound**:
- We have four compounds to analyze:
1. 1-chloro-2-methylpentane
2. 2-chloropentane
3. 1-chloropentane
4. 3-chloro-2-methylpentane

3. **Draw and Examine the Structure of Each Compound**:
- **1-chloro-2-methylpentane**:
- Structure:
- Carbon chain: C-C-C-C-C
- Chloro (Cl) at position 1 and methyl (CH3) at position 2.
- Check for chiral centers:
- The carbon at position 1 has two hydrogen atoms (not chiral).
- The carbon at position 2 has Cl, CH3, H, and the rest of the chain (chiral).
- Conclusion: This compound has a chiral center.

- **2-chloropentane**:
- Structure:
- Carbon chain: C-C-C-C-C
- Chloro (Cl) at position 2.
- Check for chiral centers:
- The carbon at position 2 has Cl, CH3, H, and the rest of the chain (chiral).
- Conclusion: This compound has a chiral center.

- **1-chloropentane**:
- Structure:
- Carbon chain: C-C-C-C-C
- Chloro (Cl) at position 1.
- Check for chiral centers:
- The carbon at position 1 has two hydrogen atoms (not chiral).
- The other carbons are either similar or have two of the same groups (not chiral).
- Conclusion: This compound does not have any chiral centers, making it achiral.

- **3-chloro-2-methylpentane**:
- Structure:
- Carbon chain: C-C-C-C-C
- Chloro (Cl) at position 3 and methyl (CH3) at position 2.
- Check for chiral centers:
- The carbon at position 3 has Cl, H, and two CH3 groups (not chiral).
- The carbon at position 2 has Cl, CH3, H, and the rest of the chain (chiral).
- Conclusion: This compound has a chiral center.

4. **Final Conclusion**:
- The only compound that does not have any chiral centers is **1-chloropentane**.

### Answer:
The achiral compound among the options is **1-chloropentane**.