What are chiral centres and chirality?

A chiral centre is an atom that has four different groups bonded to it in such a manner that it has a non-superimposable mirror image. The term “chiral centre” nowadays is also referred to the term chirality centre.

Chirality

  • Chirality is defined as an object which is asymmetric and cannot be superimposed over its mirror image is known as chiral or stereocenter. This property is known as chirality. For example- our Hand, legs etc.
  • The object which is symmetric in nature and can be superimposed over its mirror image is known as achiral. For example- cube, cone etc.
  • The chirality is due to the three-dimensional or spatial arrangements of molecules.

Stereoisomers

The isomerism that is caused by the non-similar arrangements of atoms or functional groups belonging to an atom in space is called Stereoisomers. These types of isomers have the same constitutions, but different geometric arrangements of atoms. Stereoisomers can be broadly classified into two types, namely enantiomers and diastereomers.

Enantiomers and diastereomers are two types of stereoisomers.

  • Enantiomers include mirror images and non-superimposable chiral centres.
  • Diastereomers contain non-superimposable chiral centres, but are not mirror images. Depending on the number of stereocenters, there could be far more than 2.

Enantiomers

  • When two isomers are mirror images of each other, the type of isomerism is called enantiomerism and these isomers are referred to as enantiomers.
  • Enantiomers are the stable and isolable compounds that differ in their spatial arrangements in 3-D space.
  • They generally exist as discreet pairs.
  • The properties of enantiomers are identical. However, their interaction with a plane of polarized light can vary.
  • The direction in which they rotate the plane-polarized light is different, that is, if one rotates in the right direction, the other rotates towards the left.

Enantiomers

Diastereomers

  • When two isomers do not behave as mirror images of each other, they are called diastereomers.
  • A molecule with ‘n’ number of asymmetric carbon atoms can have up to ‘2n’ diastereomers.
  • When two diastereomers differ at only one stereocenter, they are referred to as epimers.
  • These isomers vary in physical properties and chemical reactivity.

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