Question

Which of the following statement(s) about the given structures is/are correct?

• A. (I) and (IV) are C-3 epimers
• B. (II) and (III) are C-4 epimers
• C. (I) and (III) are C-2 epimers
• D. (II) and (IV) are C-3 epimers

Answer 1

Answer: (B), (D)

(II) and (IV) are C-3 epimers

When there is a change in configuration at only one chiral centre in a pair of molecule, this pair is called as epimers.

(I) and (II) are C-2 epimers
(II) and (III) are C-4 epimers
(II) and (IV) are C-3 epimers
(I) and (IV) are not epimers because more than one chiral centre has change in configuration. Similarly (I) and (III) are not epimers.

Trick: MAGI; for remembering epimers of glucose.
M-mannose; epimer at $C-2$
A-allose; epimer at $C-3$
G-galactose; epimer at $C-4$
I-Idose; epimer at $C-5$