`C_2` - epimer of D - Glucose is

Options

A. D - glucose
B. D - allose
C. D - altrose
D. D - mannose

Answer

To determine the C2 epimer of D-glucose, we will follow these steps:

### Step 1: Understand D-Glucose Structure
D-Glucose is an aldohexose with the molecular formula C₆H₁₂O₆. It has the following structure in its Fischer projection:
- The first carbon (C1) has an aldehyde group (CHO).
- The hydroxyl (OH) groups are arranged around the carbon chain.

### Step 2: Draw the Fischer Projection of D-Glucose
In the Fischer projection of D-glucose, the configuration is as follows:
1. C1: CHO
2. C2: OH on the right
3. C3: OH on the left
4. C4: OH on the right
5. C5: OH on the right
6. C6: CH₂OH

### Step 3: Identify the Chiral Carbons
D-Glucose has four chiral centers at C2, C3, C4, and C5.

### Step 4: Define Epimers
Epimers are diastereomers that differ in configuration at only one specific chiral center. In this case, we want to find the epimer at C2.

### Step 5: Change the Configuration at C2
To create the C2 epimer of D-glucose (which we will call D-mannose), we need to change the configuration at C2:
- In D-glucose, C2 has OH on the right.
- In D-mannose, we will place OH on the left.

### Step 6: Write the Structure of D-Mannose
The structure of D-mannose in Fischer projection will be:
1. C1: CHO
2. C2: OH on the left (changed from D-glucose)
3. C3: OH on the left
4. C4: OH on the right
5. C5: OH on the right
6. C6: CH₂OH

### Final Answer
The C2 epimer of D-glucose is **D-mannose**.

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