Question

The C-2 epimer of D-glucose is

• A. D-Mannose
• B. D-Fructose
• C. D-Galactose
• D. D-Gulose

Hint:

When identifying epimers, focus on the specific chiral center that differs in configuration between the two sugars.

Answer 1

The Correct Option is A

The question asks for the C-2 epimer of D-glucose. In carbohydrate chemistry, epimers are pairs of monosaccharides that differ only at one chiral center. To solve this, we need to identify the C-2 epimer of D-glucose from the given options. Let's go through each option:

1. D-Glucose: The structure of D-glucose is: 
   \(\text{H--(C=O)--(CHOH)--(CHOH)--(CHOH)--CH}_2\text{OH}\) But C-2 epimer of D-glucose would have a different configuration at the C-2 chiral center.
2. D-Mannose: D-Mannose is the C-2 epimer of D-glucose. In the Fischer projection, D-mannose has the hydroxyl group on the left side at the C-2 position, which is opposite to the configuration in D-glucose. Hence, the correct answer is D-Mannose.
3. D-Fructose: D-fructose is a ketohexose and not an epimer of D-glucose as it differs at the carbonyl group (C=O position).
4. D-Galactose: D-Galactose differs from D-glucose at the C-4 position, not the C-2 position, so it is not the C-2 epimer of D-glucose.

Therefore, the C-2 epimer of D-glucose is D-Mannose.