Which of the following is optically active

Options

A. Ethylene glycol
B. Oxalic acid
C. Glycerol
D. Tartaric acid

Explanation

To determine which of the given compounds is optically active, we need to identify if any of them possess a chiral center. A chiral center is typically a carbon atom that is bonded to four different substituents. Here’s how we can analyze each compound step by step:

### Step-by-Step Solution:

1. **Understanding Optical Activity**:
- Optical activity refers to the ability of a compound to rotate plane-polarized light. This property is generally associated with chiral molecules, which lack an internal plane of symmetry.

2. **Identifying Chiral Centers**:
- A chiral center is a carbon atom that is bonded to four different groups. If a molecule has at least one chiral center, it is considered optically active.

3. **Analyzing Ethylene Glycol**:
- Ethylene glycol has the structure:
\[ \text{HO-CH}_2\text{-CH}_2\text{-OH} \]
- In this molecule, both carbons are attached to two hydrogen atoms and one hydroxyl group. Since there are no carbon atoms with four different substituents, ethylene glycol is **not optically active**.

4. **Analyzing Oxalic Acid**:
- Oxalic acid has the structure:
\[ \text{HOOC-COOH} \]
- Both carbon atoms are bonded to two identical carboxylic acid groups. Therefore, there are no chiral centers in oxalic acid, making it **not optically active**.

5. **Analyzing Glycerol**:
- Glycerol has the structure:
\[ \text{HO-CH}_2\text{-CHOH-CH}_2\text{-OH} \]
- The first and last carbon atoms are each bonded to two hydrogen atoms, and the middle carbon is bonded to one hydroxyl group and one hydrogen atom, but it also has two identical groups. Thus, glycerol does not have any chiral centers and is **not optically active**.

6. **Analyzing Tartaric Acid**:
- Tartaric acid has the structure:
\[ \text{HOOC-CHOH-CHOH-COOH} \]
- In tartaric acid, the two middle carbons are bonded to different groups (hydroxyl and hydrogen) and thus can be considered chiral centers. Therefore, tartaric acid has chiral centers and is **optically active**.

### Conclusion:
Based on the analysis, the compound that is optically active is **tartaric acid**.