Question

\(\alpha\)-D-glucose and \(\beta\)-D-glucose differ from each other with respect to the:

• A. size of the hemiacetal ring
• B. configuration at the C₂ carbon
• C. number of -OH groups
• D. configuration at the C₁ carbon

Hint:

The two cyclic forms are anomers: only the -OH at the anomeric carbon C1 points in a different direction.

Answer 1

The Correct Option is D

Step 1: Start from the open chain:
Open-chain D-glucose is a single compound with an aldehyde group at C1 and four chiral carbons C2 to C5.
When it cyclises, the C5 oxygen attacks C1.

Step 2: Count what changes:
Only C1 becomes a new stereocentre during this ring closure. The other carbons keep their configuration.
The product with -OH at C1 trans to the CH₂OH group (down) is the \( \alpha \) form. The cis arrangement (up) is the \( \beta \) form.
Because they differ at just one stereocentre and are not mirror images, they are diastereomers called anomers.

Step 3: Rule out the others:
Ring size, the number of -OH groups and the configuration at C2 are identical in both anomers. These points can be used to tell glucose from fructose or from furanose forms, but not \( \alpha \) from \( \beta \).

Final Answer:
\( \alpha \)- and \( \beta \)-glucose differ in the configuration at C1, option (D).