Conformational and configurational isomerism.

What is conformational and configurational isomerism? 

What is conformational isomerism ?

Conformational isomerism  is a part of stereo isomerism that arises owing to the rotation of one part of the molecule with respect to another part about a single bond.The most stable conformation is also called conformers or rotamers.

What is conformation of a molecule ?

In stereochemistry conformation  of a molecule is the different spatial arrangement of its atom and groups that arises owing to the rotation of one part of the molecule with respect to another part about a single bond. Conformation are non isolable .

Conformation are easily inter-convertible. They are inter-convertible  even at room temperature .

              

3D conformation of ethane molecule.Eclipsed conformation of ethane molecule in flying wedge formula.

What is conformational isomers ?

 Conformational isomers are a number of stereo isomers  that arises  owing to the rotation of one part of the molecule with respect to another part about a single bond.

The confomational isomers of ethane molecule in flying wadge, Fisher, Newman form are shown here below.

What is configurational isomerism ?

Configurational isomerism is a part of stereo isomerism that arises due to the spatial arrangement of atoms and groups about a rigid part of the molecule,that is, about a double bond or ring and about a dissymmetric part of the molecule.

Actually, geometrical and optical isomerism are together called configurational isomerism.

An example of configurational isomerism is 1-bromo-1-chloro-ethanol.

What is configuration of a molecule ?

In stereochemistry configuration of a molecule is the different spatial arrangement of its atom and groups  about a rigid part of the molecule that is, about a double bond or ring and about a dissymmetric part of the molecule .

Configuration are  isolable . Configuration are not easily inter-convertible.

What is configurational isomers ? 

Configurational  isomers are a number of stereo isomers that arises owing to spatial arrangement of atoms and groups about a rigid part of the molecule,that is, about a double bond or ring and about a dissymmetric part of the molecule.

An example of configurational  isomers are shown by  hexa-2,4-diene.

Practice problems

• What is conformation of a molecule ? 
• What is configuration of a molecule ? 
• What is difference between conformation and configuration of a molecule ?
• What is confomational isomerism ?
• What is configurational isomerism ? 

Racemic modification and epimers.