Question

The C-2 epimer of D-glucose is:

• A. D-Mannose
• B. L-Fructose
• C. D-Gluco pyranose
• D. L-Arabinose

Answer 1

The Correct Option is A

To determine the C-2 epimer of D-glucose, we need to understand the concept of epimers in organic chemistry. Epimers are pairs of stereoisomers that differ in configuration at only one stereogenic center out of the several present in the compound. In the case of aldoses, each carbon atom with a hydroxyl group is a stereogenic center. D-glucose and D-mannose are both aldohexoses that differ only at the C-2 position. Therefore, they are C-2 epimers of each other.

Now, let's analyze the given options to see which one matches the criteria:

1. D-Mannose: It is an epimer of D-glucose at the C-2 position. In D-glucose, the hydroxyl group on C-2 is on the right, whereas in D-mannose, it is on the left.
2. L-Fructose: This is a ketohexose and not an epimer of D-glucose, which is an aldohexose.
3. D-Gluco pyranose: This is simply another form of D-glucose when in cyclic structure; not an epimer.
4. L-Arabinose: This is an aldopentose and not related to D-glucose as a C-2 epimer.

Therefore, the correct answer is D-Mannose as it is the C-2 epimer of D-glucose.

Here is a structural representation of the C-2 configuration difference between D-glucose and D-mannose: