Optical activity is expected for .

Answer

To determine which compound exhibits optical activity, we need to analyze the structures of the given acids: 2-methylpropenoic acid and 2-chloropropenoic acid. Optical activity arises from the presence of chiral centers in a molecule. A chiral center is typically a carbon atom that is sp3 hybridized and bonded to four different substituents.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **2-Methylpropenoic Acid**: The structure can be drawn as follows:
- It has a double bond between the first and second carbon atoms, with a methyl group attached to the second carbon.
- **2-Chloropropenoic Acid**: The structure can be drawn as follows:
- It has a double bond between the first and second carbon atoms, with a chlorine atom and a methyl group attached to the second carbon.

2. **Determine Hybridization**:
- For **2-methylpropenoic acid**, the second carbon (the one with the methyl group) is sp2 hybridized because it is involved in a double bond.
- For **2-chloropropenoic acid**, the second carbon is also sp2 hybridized due to the presence of a double bond.

3. **Check for Chiral Centers**:
- A chiral center must be sp3 hybridized and bonded to four different groups.
- In **2-methylpropenoic acid**, the second carbon has two identical methyl groups, which means it does not have four different substituents. Therefore, it is not chiral.
- In **2-chloropropenoic acid**, the second carbon is bonded to a chlorine atom, a methyl group, a hydrogen atom, and the rest of the molecule, making it a chiral center since all four substituents are different.

4. **Conclusion**:
- Since only **2-chloropropenoic acid** has a chiral center, it is the only compound that exhibits optical activity.

### Final Answer:
Optical activity is expected for **2-chloropropenoic acid**.

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