The amino acid which Is not optically active is

Options

A. lactic acid
B. serine
C. alanine
D. glycine

Answer

To determine which amino acid is not optically active, we need to understand the concept of optical activity and chirality.

### Step-by-Step Solution:

1. **Understanding Optical Activity**:
- An amino acid is optically active if it has a chiral center. A chiral center is typically a carbon atom that is bonded to four different groups.

**Hint**: Remember that chirality is essential for optical activity.

2. **Identifying Chiral Centers**:
- For an amino acid to be optically active, it must not have a plane of symmetry or a center of symmetry. If it has either, it will be optically inactive even if it has a chiral center.

**Hint**: Look for the presence of symmetry in the molecular structure.

3. **Analyzing the Given Amino Acids**:
- The options provided are lactic acid, serine, alanine, and glycine.
- Let's analyze each:
- **Lactic Acid**: Has a chiral center (one carbon bonded to four different groups).
- **Serine**: Has a chiral center (one carbon bonded to four different groups).
- **Alanine**: Has a chiral center (one carbon bonded to four different groups).
- **Glycine**: The structure of glycine is NH2-CH2-COOH. The central carbon (C) is bonded to two hydrogen atoms and two other groups (NH2 and COOH).

4. **Determining the Optical Activity of Glycine**:
- Glycine does not have a chiral center because it has two identical hydrogen atoms attached to the central carbon. Therefore, it does not meet the requirement of having four different groups.

**Hint**: Identify if the central carbon has four distinct substituents.

5. **Conclusion**:
- Since glycine does not have a chiral center, it is not optically active. Thus, the answer to the question is glycine.

### Final Answer:
The amino acid which is not optically active is **glycine**.