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What is Stereoisomerism?

by Joy_Chemistry

Stereoisomerism is a kind of isomerism, that occurs by arrangements of atoms or the functional groups that belong to atoms that are not similar in nature.

Isomerism are compounds that have different structure but same formulaI

In other words, similar terms they have the same constituents but differ in structure and characteristics. These compounds also differ in their physical and chemical properties

Isomers  can be generally classified into two types:

1.Constitutional Isomers- These isomers have the same parts but differ in connectivity. They can be classified into chain, position and functional group isomers

2. Stereoisomers- On the contrary, the stereoisomer of a molecule will have the same connectivity, but differ in orientation in space


Stereoisomerism refers to “this type of isomerism occurs by arrangements of atoms or the functional groups that belong to atoms that are not similar in nature. In this type of isomers, there are different geometric  arrangements of atoms, but the same constitution of atoms. Stereoisomers are classified broadly into two types, namely enantiomers and diastereomers.

1. Enantiomers

  • Isomers that are mirror images of each other , in other words this type of isomerism is enantiomerism and the respective isomers are enantiomers.
  • These compounds show differences in their spatial arrangement in 3-D space, however they are stable and can be isolated.
  • Additionally ,Enantiomers are present in pairs that are discrete.
  • Identical properties are seen in enantiomers, but their plane polarization of light interactions can differ.
  • The rotation about the plane polarized light is different , which means that if one rotates towards the left the other rotates toward the right.

2. Diastereomers

  • They are diastereomers ,as these isomers are not mirror images of each other..
  • Molecules that show asymmetric carbon atoms can possess ‘2n’ diastereomers.
  • When both diastereomers , differ only at the stereocenter, they are called as Epimers, and differ in chemical reactivity and physical properties

In the 19th century Emil Fischer a German chemist proved that carbohydrates, like fructose and glucose have similar molecular formula.

They vary in properties and structural arrangements, very simple and relative variations in geometric and spatial arrangements.

All biological systems exhibit stereoisomerism

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