Which of the following compounds will show meso isomer ?

Options

A. 2-Chlorobutane
B. 2, 3-Dichlorobutane
C. 2, 3-Dichloropentane
D. 2-Hydroxypropanoic acid

Answer

To determine which of the given compounds shows a meso isomer, we need to understand the characteristics of meso compounds. A meso compound has two or more chiral centers but is achiral due to the presence of a plane of symmetry.

Let's analyze each option step by step:

### Step 1: Analyze 2-chlorobutyne
- **Structure**: CH3-CH(Cl)-C≡C-H
- **Chiral Centers**: There is one chiral center at the carbon with the chlorine atom.
- **Plane of Symmetry**: There is no plane of symmetry in this compound.
- **Conclusion**: 2-chlorobutyne is not a meso compound.

### Step 2: Analyze 2,3-dichlorobutyne
- **Structure**: CH3-CH(Cl)-CH(Cl)-CH3
- **Chiral Centers**: There are two chiral centers (the two carbons that have chlorine attached).
- **Plane of Symmetry**: There is a plane of symmetry present in this compound.
- **Conclusion**: 2,3-dichlorobutyne is a meso compound.

### Step 3: Analyze 2,3-dichloropentene
- **Structure**: CH3-CH(Cl)-CH=CH-CH3
- **Chiral Centers**: There are two chiral centers.
- **Plane of Symmetry**: There is no plane of symmetry in this compound.
- **Conclusion**: 2,3-dichloropentene is not a meso compound.

### Step 4: Analyze 2-hydroxypropanoic acid
- **Structure**: CH3-CH(OH)-COOH
- **Chiral Centers**: There is one chiral center.
- **Plane of Symmetry**: There is no plane of symmetry in this compound.
- **Conclusion**: 2-hydroxypropanoic acid is not a meso compound.

### Final Conclusion
Based on the analysis, the only compound that shows a meso isomer is **2,3-dichlorobutyne** (Option B).

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