Anomers are stereoisomers differing in configuration at the anomeric carbon, typically found in cyclic sugar molecules, while epimers differ at only one chiral carbon. Both types are formed due to variations in the position of an –OH group and are commonly associated with sugar structures. The key distinction is that anomers specifically involve the anomeric carbon, whereas epimers can be either acyclic or cyclic.

1. What are Anomers
Anomers are stereoisomers that occur due to the difference in the configuration at their
anomeric carbon. Anomeric carbon is the carbon atom that has an aldehyde and
ketone group in the acyclic form of a sugar molecule. Sugar molecules are composed of
an aldehyde or ketone group at one end and an alcohol group at the other end of the
acyclic form of the sugar molecule. In order to become more stable, these groups of the
two ends can react with each other forming a cyclic sugar 3molecule. In this cyclic form,
the anomeric carbon has a –OH group attached to it. The position of this –OH group in
one anomeric molecule is in the opposite direction to that of the other molecule
The conversion of one anomeric form to the other anomeric form is called anomerization. This
is a reversible process. However, both anomers are stable molecules with a cyclic structure.
The two anomers are named alpha (α) anomer or beta (β) anomer. As shown in the above
image, the –OH group attached to the anomeric carbon of alpha anomer is in the opposite
direction to that of the beta anomer of glucose. The anomeric carbon is given in a green color.
What are Epimers
Epimers are a type of stereoisomers that are different from each other only at one chiral
carbon. Epimers are a type of diastereomers Although there are more than one chiral
carbons, epimers differ from each other only at one carbon center. Epimers are not
mirror images of each other.

2. As shown in the above image, D-glucose and D-mannose are epimers of each other. The blue
colored part indicates the location where isomerism has occurred. Here, the –OH group is
directed to the left side in D-mannose where it is in the right side for D-glucose. Other carbon
atoms are also chiral carbons in those molecules, but are identical to each other. Therefore,
the carbon atom where the isomerism has occurred is called the epimeric carbon.
Similarities Between Anomers and Epimers
• Anomers and epimers types are stereoisomers.
• Both types are formed due to the difference at one carbon atom.
• Both types are commonly found in sugar molecules.
• Isomerism occurs due to the differences in the position of one –OH group
attached to a carbon.
Difference Between Anomers and Epimers
Definition

3. Anomers: Anomers are stereoisomers that occur due to the difference in the
configuration at their anomeric carbon.
Epimers: Epimers are a type of stereoisomers that are different from each other only
at one chiral carbon.
Carbon where Isomerism occurs
Anomers: Isomerism occurs at anomeric carbon of the anomers.
Epimers: Isomerism occurs at the epimeric carbon of the epimers.
Structure of Sugar Molecule
Anomers: Anomers are cyclic molecules.
Epimers: Epimers can be either acyclic or cyclic molecules.
Prepared by : Afaq Miraj ( Dept Of Chemistry , University Of Wah)