# Can anyone explain to me how to identify epimers and anomers in carbohydrates (sugars)? Also, state examples.

Jul 21, 2015

Epimers and anomers are both optical isomers that differ in the configuration at a single carbon atom, but there is a difference in their definitions.

#### Explanation:

Epimers

Epimers are optical isomers that differ in the configuration of a single carbon atom

For example, D-galactose and D-mannose are epimers of D-glucose.

D-Galactose is an epimer of D-glucose because the two sugars differ only in the configuration at $\text{C-4}$.

D-Mannose is an epimer of D-glucose because the two sugars differ only in the configuration at $\text{C-2}$.

Anomers

When a molecule such as glucose converts to a cyclic form, it generates a new chiral centre at $\text{C-1}$.

(from www.chem.ucalgary.ca)

The carbon atom that generates the new chiral centre ($\text{C-1}$) is called the anomeric carbon.

Anomers are special cases — they are epimers that differ in configuration only at the anomeric carbon.

For example, α-D-glucose and β-D-glucose are anomers.

(from wikispaces.psu.edu)

The α form has the anomeric $\text{OH}$ group at $\text{C-1}$ on the opposite side of the ring from the $\text{CH"_2"OH}$ group at $\text{C-5}$.

The β form has the anomeric $\text{OH}$ group on the same side as the $\text{CH"_2"OH}$.

In D-fructose, the carbonyl group is at $\text{C-2}$.

(fromweb.pdx.edu)

Here, $\text{C-2}$ is the anomeric carbon.

(From pinterest.com)

α-D-Fructofuranose and β-D-fructofuranose are anomers.