Which of the isomers of n-butyl alcohol exhibit optical isomerism ?

Options

A. Butyl alcohol
B. Sec.Butyl alcohol
C. 2-Methyl-1-propanol
D. 2-Methyl-2-Propanol

Answer

To determine which isomers of n-butyl alcohol exhibit optical isomerism, we need to analyze the structures of the possible isomers and identify if they have a chiral center. A chiral center is a carbon atom that is bonded to four different groups.

### Step-by-Step Solution:

1. **Identify the Isomers of Butyl Alcohol**:
The isomers of butyl alcohol (C4H10O) include:
- n-Butyl alcohol (1-butanol)
- Isobutyl alcohol (2-methyl-1-propanol)
- Sec-butyl alcohol (2-butanol)
- Tert-butyl alcohol (2-methyl-2-propanol)

2. **Check for Chiral Centers**:
- **n-Butyl Alcohol (1-butanol)**:
Structure: CH3-CH2-CH2-CH2OH
- No chiral center (all carbons have at least two identical groups).

- **Isobutyl Alcohol (2-methyl-1-propanol)**:
Structure: (CH3)2CH-CH2OH
- No chiral center (the carbon with the OH group is attached to two identical CH3 groups).

- **Sec-Butyl Alcohol (2-butanol)**:
Structure: CH3-CH(OH)-CH2-CH3
- Has a chiral center at the second carbon (attached to CH3, OH, CH2, and CH3 - all different).

- **Tert-Butyl Alcohol (2-methyl-2-propanol)**:
Structure: (CH3)3C-OH
- No chiral center (the carbon with the OH group is attached to three identical CH3 groups).

3. **Conclusion**:
The only isomer of butyl alcohol that exhibits optical isomerism is **sec-butyl alcohol (2-butanol)** because it has a chiral center.

### Final Answer:
**Sec-butyl alcohol (2-butanol)** exhibits optical isomerism.