Which of the following compounds can exhibit enantiomerism?

Options

A. 3-hydroxy propanoic acid
B. 3-hydroxy butanoic acid
C. 4-hydroxy butanoic acid
D. none of these

Explanation

To determine which of the given compounds can exhibit enantiomerism, we need to identify if any of the compounds contain a chiral carbon. A chiral carbon is a carbon atom that is attached to four different groups, leading to non-superimposable mirror images known as enantiomers.

### Step-by-Step Solution:

1. **Understand Enantiomerism**: Enantiomers are pairs of molecules that are mirror images of each other but cannot be superimposed. For a compound to exhibit enantiomerism, it must have at least one chiral carbon atom.

2. **Identify Chiral Carbons**: A chiral carbon is typically a carbon atom bonded to four different substituents. We will analyze the structures of the given compounds to identify any chiral carbons.

3. **Draw Structures**:
- **3-Hydroxypropanoic Acid**:
- Structure: CH3-CH(OH)-C(=O)OH
- In this structure, the second carbon (C2) has four different groups:
- Hydroxyl group (OH)
- Hydrogen (H)
- Methyl group (CH3)
- Carboxylic acid (COOH)
- Therefore, this carbon is chiral and can exhibit enantiomerism.

- **3-Hydroxybutanoic Acid**:
- Structure: CH3-CH(OH)-CH2-C(=O)OH
- The third carbon (C3) is also attached to four different groups:
- Hydroxyl group (OH)
- Hydrogen (H)
- Methyl group (CH3)
- Ethyl group (C2H5)
- This carbon is also chiral and can exhibit enantiomerism.

- **4-Hydroxybutanoic Acid**:
- Structure: CH3-CH2-CH(OH)-C(=O)OH
- The third carbon (C3) is not chiral because it is bonded to two hydrogen atoms and does not have four different substituents.

4. **Conclusion**: Among the compounds analyzed, both 3-hydroxypropanoic acid and 3-hydroxybutanoic acid can exhibit enantiomerism due to the presence of chiral carbons. However, 4-hydroxybutanoic acid does not have a chiral carbon and cannot exhibit enantiomerism.

### Final Answer:
The compounds that can exhibit enantiomerism are **3-hydroxypropanoic acid** and **3-hydroxybutanoic acid**.