What is Epimer?

Epimer:

Epimers are the optical stereoisomers which differ with respect to the spatial configuration around only one asymmetric carbon out of more than one asymmetric carbon in the molecule.

 e,g.  Glucose and Mannose (they are C2 epimers)
         Glucose and Galactose (they are C4 epimers)

Isomer: Definition, Types.

Isomer:

Definition:

Isomers are substances having same molecular (chemical) formula, but different structure or having
same molecular formula and identical structural form, but different spatial configuration around one
or more carbon. Isomerism is the processes of formation of isomers.

Types of isomer:

1. Structural isomer
2. Stereo isomer (Space isomer)
• Geometric isomer
• Cis variety
• Trans variety

•  Optical isomer
• Optical enantiomers
• Diasteroisomers

Structural Isomer:

These are the substances having same molecular (chemical) formula, but different structure. These
type of isomers differ with respect to physical and chemical properties.
e.g.     CH3-CH2-CH2-CH3 (Butane)
           
                     CH3

           CH3-CH-CH3 (Isobutane)

Stereo Isomer (Space Isomer)

Substances having same molecular formula as well as identical structural form, but different with
respect to the spatial configuration of atoms or groups around one or more carbon. This type of
isomers sometimes shows identical physical and chemical properties.
Spatial configuration means
o Arrangement of atoms or groups around a carbon in relation to space,
o Three dimensional space relationship of atoms or groups around a carbon.

Types of stereo isomer:

1. Geometric isomer
2. Optical isomer
• Optical enantiomers
• Diastereoisomers