At which carbon are the following sugars epimers of each other?

Question

Quizplus · Accepted Answer

Epimers are two sugars that differ in the configuration at only one carbon atom. In this case, since the two sugars are different by only one OH group, they must differ at the anomeric carbon (carbon 1) or at one of the other hydroxyl-bearing carbons (carbons 2-5). Inspecting the two sugars, we can see that they differ at carbon 3 (the carbon bearing the OH group in the middle of the molecule), so the correct answer is C) C-3.

At Which Carbon Are the Following Sugars Epimers of Each