Stereogenic center or Stereocenter

The stereogenic center is also known as the stereocenter. In the stereogenic center exchange of two groups bonded to the same atom produce new stereoisomers. It may have a single bond or a double bond around the central atom. This is used to explain the stereochemistry of a molecule. Stereocenters may be tetrahedral or trigonal.

example of stereocenter

When an atom is bonded to three or more different groups and the exchange of two groups led to the formation of new stereoisomers then the central atom of the molecule is known as the stereogenic center. Stereoisomers have the same connectivities but are different in position of the same group in three-dimensional space.

At the stereogenic center interchange of two groups produce two stereoisomers. Interchange of groups means breaking of covalent bonds because we are dealing with the molecular model. Any atom having a stereocenter is known as a stereogenic atom. Stereogenic atoms may be sp3 or Sp2 hybridized.

Stereocenters have different configurations. These are drawn with dashes and wedges to show the configurations. They may have R or S configuration. The molecule may have one or more stereocenters. A molecule with one stereocenter can have two isomers.

Formula:

1 Stereocenters = 2 Stereoisomers or (maximum stereoisomers)

n = 2n

Here,

  • n = stereocenters
  • 2n = stereoisomers

Chiral center

The chiral center is the type of stereocenter. When an atom is bonded to four different groups then the central atom is called as chiral central. It is the origin of chirality. All the chiral centers are stereocenters but all stereocenters are not chiral centers. These are tetrahedral stereocenters.

2-butanol example of chiral center

2-Butanol is an example of a chiral center. The red star represents the chiral center. They must have four different groups attached to the central atom. These are Sp3 hybridized. They are asymmetric centers. Their mirror images are non-superimposable. They do not have a plane of symmetry.

Identification of stereocenters

We can identify the stereocenter in the molecule as.

  • If the central atom is connected to four different groups then the central atom is a stereocenter. Because the exchange of two groups produces new stereoisomers. For example,

example of stereocenter identification of stereocenter tetrahedral stereocenter

These two molecules have the same constitution but they differ in the arrangement of the same groups in three-dimensional space. They have different configurations.

  • If a central atom is bonded to three different groups and the exchange of two groups produces new stereoisomers then it is a stereocenter.

This molecule has two stereocenters. And swapping of groups around any stereocenter leads to the formation of a new stereoisomer. example of stereocenter identification of stereocenter trigonal steeocenter

Sterocenter Vs Chiral Center

ComparisonStereocenter Chiral center
Definition The central atom is attached to three or more different groups.The central atom is attached to four different groups.
Hybridization Sp3 or Sp2Sp3
BondingSingle or double bond around central atomSingle bonds
Plane of symmetry May or may notA symmetrical
Geometry Trigonal or tetrahedraltetrahedral
Swapping of groupsResults in stereoisomersResults in enantiomers

Examples of the stereogenic center

Trigonal stereocenter

When a central atom is bonded to the three different groups then they have trigonal stereocenters. They have a double bond around the central atom. Similarly, they have Sp2 hybridization. They result in cis, trans isomers.

cis-1,2-dicholorethene example of trigonal stereoenter

Cis-1,2-Dichloroethene is an example of a stereogenic center. It has two stereogenic centers. The exchange of two groups around any stereocenter produces a new stereoisomer. This is the molecule that has a stereocenter but not a chiral center.

Tetrahedral stereocenter

When a central atom is bonded to four different groups then they have tetrahedral stereocenters. They have single bonds around the central atom. Similarly, they have Sp3 hybridization. They result in enantiomers. These can also be classified as chiral centers.

example of tetrahedral sterogenic center

Molecules having more than one stereocenter and a plane of symmetry are also called as meso compounds.

Molecules with multiple stereogenic centers

glucose molecule example of molecule with multiple stereocenters example of multiple stereocenters

Concepts berg

What is a stereogenic center?

An atom bonded to three or four different groups and exchange of two groups produce new stereoisomers then this atom is known as a stereogenic center.

How we can identify a stereogenic center?

We can identify the stereogenic center as

  • They have three or four different substituents.
  • Exchange of two groups produces new stereoisomers.
  • They have different configurations.

Give examples of chiral molecules without the stereogenic center.

The substituted biphenyls and substituted allenes are examples of chiral molecules without stereocenters.

Is the chiral center the same as the stereogenic center?

The chiral center is the type of stereocenter. All the chiral centers are stereocenters but all stereocenters are not chiral centers.

What is stereogenic carbon?

A carbon atom bonded to three or four different groups and exchange of two groups produce a new stereoisomer is called stereogenic carbon.

What is chiral carbon?

A carbon atom that has four different substituents is called chiral carbon.

What is the difference between a stereogenic center and a chiral center?

How many stereogenic centers are there in a compound?

Is stereogenic center same as chiral

Do chiral molecules have to have a stereocenter

References

  • 12th edition of Organic Chemistry by T.W Graham Solomons, Craig B. Fryhle, and Scott A. Synder.
  • Chiral vs Achiral vs Meso compounds by psiberg.com
  • 4th edition of Organic Chemistry As a second language by David Klein.

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