`alpha`-D - Glucose from `beta`-D-glucose due to difference in one of the carbon atoms with respect to its

Options

A. number of -OH groups
B. configuration
C. conformation
D. size of hemiacetal ring

Answer

To understand the difference between alpha-D-glucose and beta-D-glucose, we need to analyze their structures and the specific carbon atom that differentiates them.

### Step-by-Step Solution:

1. **Understanding the Structure of Glucose**:
- Glucose is a six-membered ring structure known as pyranose. It has a carbonyl group (C=O) that reacts with a hydroxyl group (–OH) to form a hemiacetal.

2. **Identifying the Anomeric Carbon**:
- The anomeric carbon is the carbon atom that was part of the carbonyl group before the ring formation. In D-glucose, this is carbon 1 (C1).

3. **Drawing Alpha-D-Glucose**:
- In alpha-D-glucose, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned downwards (below the plane of the ring).

4. **Drawing Beta-D-Glucose**:
- In beta-D-glucose, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned upwards (above the plane of the ring).

5. **Comparing the Two Forms**:
- The key difference between alpha-D-glucose and beta-D-glucose is the orientation of the hydroxyl group on the anomeric carbon (C1).
- In alpha-D-glucose, it is trans to the CH2OH group on C6, while in beta-D-glucose, it is cis to the CH2OH group.

6. **Conclusion**:
- Therefore, the difference between alpha-D-glucose and beta-D-glucose is due to the configuration of the hydroxyl group on the anomeric carbon. This configuration is what distinguishes the two forms.

### Final Answer:
Alpha-D-glucose differs from beta-D-glucose due to the configuration of the hydroxyl group on the anomeric carbon (C1).

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