What are Epimers? A complete overview


Epimers are types of stereoisomers of carbohydrates that differ in the location of the -OH group in one location. The best examples are D-glucose and D-galactose.



Epimers are varied in one position for the placement of the -OH group. D-glucose and D-galactose are D-sugars, which means that the -OH group on carbon -5 of these hexoses is located on right in Fischer projection the single difference between D-glucose and D-galactose is on carbon-4 as given in the following image.




  • For D-glucose, the -OH is on the right in Fischer projection and for D-galactose the -OH is on the left.
  • and this difference makes these two hexoses epimers.
  • remember these two are not the enantiomers or diastereomers or isomers these are only epimers.

Characteristics of Epimers:

  • Epimers contain more than one chiral carbon but differ from each other in the configuration of only one chiral carbon.
  • These are different from each other at only or few chiral carbons, but not all.
  • not mirror images of each other.
  • Their physical and chemical properties are different from each other.

Epimeric carbons: In epimers chiral carbon atoms whose absolute configuration makes the two compounds different are called epimeric carbons.



Epimerization: is the chemical process of the interconversion of one epimer to the other epimer and there is a change in one chiral center. It may be spontaneous or catalyzed by enzymes.

For example Stereoisomers, β-D-glucopyranose, and β-D-manno pyranose are epimers because they differ at C-2position. The hydroxy group in β-D– glucopyranose is equatorial & in the case of β-D-mannopyranose, the C-2 hydroxy group is axial. These are epimers because they do not mirror images of each other. Here is the structure of both these two molecules.






Related questions:


  1. What are epimers in biochemistry?

A pair of stereoisomers differ in the configuration of a single stereocentre. sugars glucose and galactose are epimers.

2.How do you find your epimers?

If pair of molecules has 1 stereocenter the epimers are enantiomers. and if the molecule has 2 stereocenters then epimers are diastereomers.

3.What is the difference between epimers and diastereomers?

Diastereomers are compounds consisting of two or more chiral centers and not mirror images of each other. Epimers are diastereomers containing more than one chiral center but they differ in absolute configuration at one chiral center.

4.How many epimers does glucose have?

There are four epimers of glucose with inversion of configuration at single carbon.



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