5 Difference Between Anomers And Epimers
Stereoisomers are pairs of compounds that have the same chemical formula and the same atom connectivity, but they differ in their three-dimensional orientation. Monosaccharide like glucose, fructose, mannose and galactose can show different isomerism. For example glucose and fructose are functional isomers of each other as glucose contains aldehyde group and fructose contains ketonic group in molecule. They can also show stereoisomerism due to the presence of chiral carbon atoms.
Those stereoisomers which are differing in configuration at only one chiral carbon atom are referred to as Epimers whereas those that differ in configuration at the hemiacetal carbon are referred to as anomers.
Anomers
Anomers are stereoisomers of cyclic forms of sugars or similar molecules that differ in configuration only at the hemiacetal or hemiketal carbon. The cyclic forms of carbohydrates can exist in two forms α- and β- based on the position of the substituent at the anomeric center. Anomers are designated α- if the configuration at the anomeric carbon is the same, however if the configuration differs, the anomer is designated β.
Example Of Anomers
- α-D-Glucopyranose and β-D-glucopyranose
- α-D-Fructofuranose and β-D-fructofuranose
- Methyl α-D-glucopyranoside and methyl-β-D-glucopyranoside
Anomers are different in structure and thus have different stabilizing and destabilizing effects from each other. The major contributors to the stability of certain anomers are: the anomeric effect which stabilizes the anomer that has an electron withdrawing group, hydrogen bonds between the anomeric group and other groups on the ring and dipolar repulsion between the anomeric group and other groups.
What You Need To Know About Anomers
Epimers
An epimer are a specific type of stereoisomer that have multiple stereocenters, but only differ from one another by the configuration at one of the stereogenic centers. A stereocenter or stereogenic center is a carbon atom that has four different atoms or group of atoms bonded to it.
Epimers have opposite configuration at only one of two or more chiral centers present in the respective molecular entities. For example D-glucose and D-mannose which differ only in the stereochemistry at C-2, are epimers. Also glucose and galactose are epimers of each other as they only differ in the position of hydroxyl group at C4 (chiral carbon atom).
What You Ned To Know About Epinomers
Also Read: Difference Between Aldose And Ketose
Difference Between Anomers And Epimers In Tabular Form
| BASIS OF COMPARISON | ANOMERS | EPIMERS |
| Description | The anomer is a type of stereoisomer differing in the configuration at the acetal/hemiacetal carbon (also referred to as anomeric carbon). | The epimers are a type of stereoisomers that contain more than one chiral center but differ from each other in the absolute configuration at only one chiral center. |
| Epimers | Anomers are cyclic molecules. | Epimers can be either acyclic or cyclic molecules. |
| Carbon Atom | The carbon atom where stereoisomerism occurs is the acetal/hemiacetal carbon (also referred to as anomeric carbon). | The carbon atom where stereoisomerism occurs can be any single stereogenic center. |
| Examples | Examples of anomers are α-D-Fructofuranose and β-D-Fructofuranose. | Examples of epimers are galactose and glucose. |
Similarities Between Anomers And Epimers
- They are both formed due to the difference in the position of only one hydroxyl group.
- They are both present in sugar molecules.
- Both different in one carbon atom.
- Anomers and epimers are both structural isomers.
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