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: Understanding the question:
\( \alpha \)-D-glucose and \( \beta \)-D-glucose are cyclic forms of D-glucose. We must find the one structural point where they differ.

Step 2: How the ring forms:
In open-chain glucose, the -OH on C5 adds to the aldehyde group on C1 and gives a six-membered hemiacetal (pyranose) ring.
This makes C1 a new chiral centre. It is called the anomeric carbon.
The -OH on C1 can point down (the \( \alpha \) form) or up (the \( \beta \) form) in the Haworth structure.

Step 3: Check each option:
(A) Both forms are six-membered pyranose rings, so the ring size is the same.
(B) C2 has the same configuration in both forms.
(C) Both have five -OH groups, so the number is the same.
(D) They differ only in the configuration at C1. This is correct. Such a pair is called anomers.

Final Answer:
The two forms differ in the configuration at the C1 (anomeric) carbon, option (D). \[ \boxed{\text{configuration at } C_1} \]