D - Glucose and D - Mannose are :

Options

A. enantiomers
B. functional isomers
C. epimers
D. metamers

Answer

To solve the question regarding D-Glucose and D-Mannose, we need to understand their structural characteristics and how they relate to each other.

### Step-by-Step Solution:

1. **Identify the Structures**:
- D-Glucose and D-Mannose are both six-carbon sugars (hexoses) and belong to the class of monosaccharides.
- D-Glucose has the following structure:
```
CHO
|
C1 - OH
|
C2 - OH
|
C3 - OH
|
C4 - OH
|
C5 - CH2OH
```
- D-Mannose has a similar structure, but the configuration at the second carbon (C2) is different:
```
CHO
|
C1 - OH
|
C2 - H
|
C3 - OH
|
C4 - OH
|
C5 - CH2OH
```

2. **Compare the Structures**:
- Both sugars have the same molecular formula (C6H12O6) and differ only in the configuration around one specific carbon atom (C2).
- In D-Glucose, the hydroxyl group (OH) is on the right side at C2, while in D-Mannose, it is on the left side.

3. **Define Epimers**:
- Sugars that differ in configuration at only one specific carbon atom are termed epimers.
- Since D-Glucose and D-Mannose differ at C2, they are classified as C2 epimers.

4. **Conclusion**:
- Therefore, the relationship between D-Glucose and D-Mannose is that they are epimers, specifically C2 epimers.

### Final Answer:
D-Glucose and D-Mannose are C2 epimers.

---