Question

α-D(+)glucose and β-D(+)glucose are

• A. Geometrical isomers
• B. Epimers
• C. Enantiomers
• D. Anomers

Hint:

They differ only at the anomeric carbon C1 formed on ring closure; such cyclic sugar isomers are anomers.

Answer 1

The Correct Option is D

Step 1: When glucose forms its cyclic (pyranose) structure, the open-chain aldehyde carbon (C1) becomes a new chiral centre called the anomeric carbon. Two ring forms result, differing only in the arrangement of the -OH at this C1.
Step 2: In α-D-glucose the C1 -OH points down (opposite side to the C6 CH₂OH reference), while in β-D-glucose the C1 -OH points up. They differ in configuration only at the anomeric carbon C1.
Step 3: Cyclic sugars that differ in configuration at the anomeric carbon are called anomers.
Conclusion: Option (iv) Anomers is correct. They are not enantiomers (not mirror images at all centres), not epimers (epimers differ at a carbon other than the anomeric one), and not geometrical isomers (no C=C double bond is involved).