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

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.

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.

(from biochemnoob.wordpress.com)

D-Galactose is an epimer of D-glucose because the two sugars differ only in the configuration at ##"C-4"##.

D-Mannose is an epimer of D-glucose because the two sugars differ only in the configuration at ##"C-2"##.

Anomers

When a molecule such as glucose converts to a cyclic form, it generates a new chiral centre at ##"C-1"##.

(from www.chem.ucalgary.ca

The carbon atom that generates the new chiral centre (##"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 ##"OH"## group at ##"C-1"## on the opposite side of the ring from the ##"CH"_2"OH"## group at ##"C-5"##.

The β form has the anomeric ##"OH"## group on the same side as the ##"CH"_2"OH"##.

In D-fructose, the carbonyl group is at ##"C-2"##.

(fromweb.pdx.edu)

Here, ##"C-2"## is the anomeric carbon.

(from science.uvu.edu

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