The two cyclic hemiacetal forms of glucose differing only in the configuration of the hydroxyl group at C-1 are called

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question regarding the two cyclic hemiacetal forms of glucose that differ only in the configuration of the hydroxyl group at C-1, we can follow these steps:

### Step by Step Solution:

1. **Understanding the Structure of Glucose**:
Glucose is a six-carbon sugar (hexose) that can exist in a cyclic form. The cyclic form is created when the carbonyl group (C=O) reacts with a hydroxyl group (–OH) to form a hemiacetal.

2. **Identifying the Cyclic Forms**:
The cyclic forms of glucose can be represented as a pyranose (six-membered ring). In these forms, the carbon atom that was part of the carbonyl group (C-1) becomes a new chiral center.

3. **Differentiating the Anomers**:
The two cyclic forms of glucose that differ only at the configuration of the hydroxyl group at C-1 are:
- **Alpha (α) D-Glucose**: In this form, the hydroxyl group (-OH) at C-1 is positioned on the opposite side (trans) of the CH2OH group at C-5.
- **Beta (β) D-Glucose**: In this form, the hydroxyl group (-OH) at C-1 is positioned on the same side (cis) as the CH2OH group at C-5.

4. **Defining Anomers**:
The terms used to describe these two forms are known as **anomers**. Anomers are a specific type of epimer that differ in configuration at the anomeric carbon (C-1 in this case).

5. **Conclusion**:
Therefore, the two cyclic hemiacetal forms of glucose differing only in the configuration of the hydroxyl group at C-1 are called **anomers**.

### Final Answer:
The two cyclic hemiacetal forms of glucose differing only in the configuration of the hydroxyl group at C-1 are called **anomers**.