Which of the following acids does not exhibit optical isomerism?

Options

A. Maleic acid
B. `alpha`-amino acids
C. Lactic acid
D. Tartaric acid

Explanation

To determine which of the following acids does not exhibit optical isomerism, we need to analyze the structures of the given acids and identify whether they have chiral centers or symmetry elements.

### Step-by-Step Solution:

1. **Understanding Optical Isomerism**:
- Optical isomerism occurs in compounds that are optically active, meaning they have chiral centers or lack symmetry elements (like a plane of symmetry, center of symmetry, or axis of symmetry).

2. **Analyzing Malic Acid**:
- Draw the structure of malic acid. It has the formula C4H6O5.
- Check for chiral centers: Malic acid has no carbon atom bonded to four different groups.
- Conclusion: Malic acid is optically inactive.

3. **Analyzing Alpha Amino Acids**:
- Draw the general structure of an alpha amino acid (R-CH(NH2)-COOH).
- Identify the chiral center: The carbon atom (C) attached to the amino group (NH2), carboxylic acid (COOH), hydrogen (H), and the R group is a chiral center.
- Conclusion: Alpha amino acids are optically active.

4. **Analyzing Lactic Acid**:
- Draw the structure of lactic acid (C3H6O3).
- Identify the chiral center: The carbon atom bonded to the hydroxyl group (OH), carboxylic acid (COOH), methyl group (CH3), and hydrogen (H) is a chiral center.
- Conclusion: Lactic acid is optically active.

5. **Analyzing Tartaric Acid**:
- Draw the structure of tartaric acid (C4H6O6).
- Identify chiral centers: Tartaric acid has two carbon atoms that are each bonded to four different groups.
- Conclusion: Tartaric acid is optically active.

6. **Final Conclusion**:
- Among the acids analyzed, malic acid is the only one that does not exhibit optical isomerism because it lacks a chiral center.
- Therefore, the correct answer is **malic acid**.