Question

Which of the following is the CORRECT statement about hexoses?

• A. D-mannose is C-4 epimer of D-glucose
• B. D-galactose is C-2 epimer of D-glucose
• C. D-glucose and L-glucose are diastereomers
• D. D-glucose and D-galactose are diastereomers

Hint:

Diastereomers are stereoisomers that are not related as mirror images, whereas epimers differ only at one chiral center.

Answer 1

The Correct Option is D

Step 1: Understanding epimers and diastereomers.
- Epimers are sugars that differ in configuration at only one chiral center. - Diastereomers are stereoisomers that are not mirror images of each other.
Step 2: Analyzing the options.
- (A) D-mannose is C-4 epimer of D-glucose: This is incorrect because D-mannose is actually a C-2 epimer of D-glucose. - (B) D-galactose is C-2 epimer of D-glucose: This is correct. D-galactose differs from D-glucose only at the C-4 position, making them C-2 epimers. - (C) D-glucose and L-glucose are diastereomers: This is true. D-glucose and L-glucose are non-mirror image stereoisomers (diastereomers). - (D) D-glucose and D-galactose are diastereomers: This is correct. D-glucose and D-galactose are diastereomers as they differ in the configuration at one or more chiral centers.
Step 3: Conclusion.
The correct answer is (D) because D-glucose and D-galactose are diastereomers, differing at one chiral center (C-4).