Which is the correct relation between glucose and mannose?

Options

A. Structual isomers
B. Disaccharides
C. Epimers
D. Anomers

Answer

To determine the correct relation between glucose and mannose, we can follow these steps:

### Step 1: Understand the Structures of Glucose and Mannose
- **D-Glucose** has the following structure:
- It has an aldehyde group (CHO) at one end and multiple hydroxyl (OH) groups attached to its carbon atoms.

- **D-Mannose** also has the same molecular formula (C6H12O6) but differs in the arrangement of the hydroxyl groups.

### Step 2: Draw the Structures
- Draw the Fischer projection of D-Glucose:
```
CHO
|
C
/ \
OH H
/ \
H OH
\ /
C
/ \
OH H
\ /
C
/ \
H CH2OH
```

- Draw the Fischer projection of D-Mannose:
```
CHO
|
C
/ \
OH H
/ \
H OH
\ /
C
/ \
H OH
\ /
C
/ \
H CH2OH
```

### Step 3: Compare the Structures
- Both structures have the same molecular formula (C6H12O6), indicating they are isomers.
- The only difference lies in the configuration of the hydroxyl group at the C2 position.

### Step 4: Identify the Type of Isomerism
- Since the only difference between glucose and mannose is at the C2 carbon, they are classified as **epimers**.
- Specifically, they are **C2 epimers** because the configuration differs at the second carbon atom.

### Conclusion
The correct relation between glucose and mannose is that they are **C2 epimers**.

### Final Answer
**Option 3: Epimers**

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