The aqueous solution of D - glucose contains two forms of D - glucopyranose , which are :

Options

A. Tautomers
B. Anomers
C. Epimers
D. Enantiomers

Answer

To solve the question regarding the two forms of D-glucopyranose present in an aqueous solution of D-glucose, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Forms of D-Glucopyranose**:
- D-glucose exists in two anomeric forms when it cyclizes to form a pyranose ring: **alpha (α)** and **beta (β)** D-glucopyranose.

2. **Draw the Structures**:
- **Alpha D-Glucopyranose**:
- In this form, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned **below** the plane of the ring.
- The structure can be represented as follows:
- C1: OH (down)
- C2: OH (down)
- C3: OH (up)
- C4: OH (down)
- C5: CH2OH (up)

- **Beta D-Glucopyranose**:
- In this form, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned **above** the plane of the ring.
- The structure can be represented as follows:
- C1: OH (up)
- C2: OH (down)
- C3: OH (up)
- C4: OH (down)
- C5: CH2OH (up)

3. **Understand the Difference**:
- The key difference between alpha and beta forms lies in the orientation of the hydroxyl group on the anomeric carbon (C1).
- In alpha D-glucopyranose, the -OH group is down, while in beta D-glucopyranose, the -OH group is up.

4. **Terminology**:
- The difference in the configuration at the anomeric carbon (C1) leads to the classification of these two forms as **anomers**.
- Anomers are a type of stereoisomer that differ in configuration at the anomeric carbon.

### Final Answer:
The two forms of D-glucopyranose present in an aqueous solution of D-glucose are **alpha (α) D-glucopyranose** and **beta (β) D-glucopyranose**.