Question

The $\alpha$-D-glucose and $\beta$-D-glucose differ from each other due to difference in carbon atom with respect to its

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

Answer 1

The Correct Option is C

The question asks about the difference between $\alpha$-D-glucose and $\beta$-D-glucose. To understand this, we must explore the concept of anomers in carbohydrate chemistry.

Glucose is an aldohexose, which means it has an aldehyde group and six carbon atoms. When D-glucose forms a cyclic structure, it can form two isomers known as anomers, namely $\alpha$-D-glucose and $\beta$-D-glucose. These isomers differ at the anomeric carbon (C-1 position in the case of glucose).

Here is the difference between $\alpha$-D-glucose and $\beta$-D-glucose:

1. Configuration: The configuration at the anomeric carbon is different. In $\alpha$-D-glucose, the OH group at C-1 is on the opposite side (trans) of the CH₂OH group. In contrast, in $\beta$-D-glucose, the OH group at C-1 is on the same side (cis) as the CH₂OH group.
2. Number of OH-groups: The number of hydroxyl (OH) groups in both $\alpha$-D-glucose and $\beta$-D-glucose is the same; they both have five OH groups. This is a critical point as this option was mentioned in the question but is incorrect.

Given the options provided, let's analyze which is the correct answer:

• Conformation: This usually refers to the spatial arrangement of atoms which can change without breaking bonds. Anomers are due to configurational changes, not conformational.
• Configuration: Correct, as explained, the $\alpha$ and $\beta$ forms differ in the configuration of their anomeric carbon.
• Number of OH-groups: Incorrect, since both forms have the same number of hydroxyl groups.
• Size of hemiacetal ring: This remains unchanged between $\alpha$ and $\beta$ forms.

Based on this analysis, the correct answer is configuration.