Correct option is D
The term "epimer" refers to a stereoisomer that differs in configuration at only one specific carbon atom. In the context of monosaccharides like D-glucose, epimers are sugars that differ in configuration at a single chiral center other than the anomeric carbon.
Let’s analyze the correct epimeric relationships:
- D-mannose and D-glucose differ at C-2, so D-mannose is correctly classified as a C-2 epimer of glucose.
- D-allose and D-glucose differ at C-3, so D-allose is correctly a C-3 epimer of glucose.
- D-galactose and D-glucose differ at C-4, so D-galactose is a C-4 epimer of glucose.
- D-talose, however, differs from D-glucose at both C-2 and C-4, not at C-5. Hence, it is not a C-5 epimer. Therefore, statement (d) is incorrect.
Information Booster:
- Epimers differ in configuration around only one carbon atom (except the anomeric carbon).
- D-mannose and D-glucose differ only at C-2, making D-mannose a C-2 epimer.
- D-galactose differs from D-glucose at C-4, classifying it as a C-4 epimer.
- D-allose and D-glucose differ at C-3, hence D-allose is a C-3 epimer.
- D-talose differs from D-glucose at C-2 and C-4, so it is not a simple epimer at C-5.
- The C-5 position in glucose remains the same in all its common aldose epimers, and there is no well-defined C-5 epimer of glucose.
- Knowledge of epimers is important in carbohydrate chemistry and stereochemistry, particularly in biochemical transformations and enzymatic reactions.
