Question

Three cyclic structures of monosaccharides are given below which of these are anomers.

• A. I and III
• B. II and III
• C. I and II
• D. III is anomer of I and II

Answer 1

The correct option is C I and II

Anomers are cyclic monosaccharides or glycosides, differing from each other in the configuration of $C-1$ if they are aldose or in the configuration at $C-2$ if they are ketose.

Analysing the options

Option (A):


I and II are stereoisomers, differing in configuration at $C-1$ carbon. So, they are anomers to each other.

Option (B):


II and III are not isomers to each other due to having different molecular formula as II has 6 carbons and III has 7 carbon atoms.

Option (C):



I and III are not isomers to each other due to having different molecular formula as I has 6 carbons and III has 7 carbon atoms.

Option (D):

I and II are anomers but III is not isomers to I and II due to having different molecular formula as I and II has 6 carbons and III has 7 carbon atoms.

​​​​​​​So, the correct answer is option (A).