What is Isomer?

An Isomer is molecule that has the same the same chemical formula as another molecule, but with a different molecule structure than the other molecule.

There are several types of isomers:

1. Constitutional Isomers - Isomers that differ in connectivity are called constitutional isomers, or structure isomers. They have the same parts, but those parts are attached to each other differently.

2. Stereoisomers - Isomers that have the same structure parts but that differ in the orientation of those parts in space.

2.1. Enantiomers - Isomers that are mirror images, like the left hand and right hand.

2.2. Diastereomers - Stereoisomers that are not mirror images.

2.2.1. Cis-Trans Isomers - Diastereomers that are have two idential functional groups on the same side or the opposite sides of a double bond. If the two idential functional groups are on the same side, it is called Cis Isomers. If the two idential functional groups are on the same side, it is called Trans Isomers.

2.2.2. Conformers (Conformational Isomers)

2.2.2.1. Rotamers - Conformers that have an identical structure if they are rotated about a single bonds.

Another way of dividing isomers into sub-categories:

1. Configurational Isomers - Stereoisomers that can cannot be converted into one another by rotation around a single bond.

1.1. Optical Isomers - Stereoisomers that have a chiral carbon that can cause the optical activity of a molecule. A chiral carbon is a carbon atom that has four different groups attached to it.

1.2. Geometrical (Cis-Trans) Isomers - Stereoisomers that are have two idential functional groups on the same side or the opposite sides of a double bond. If the two idential functional groups are on the same side, it is called Cis Isomers. If the two idential functional groups are on the same side, it is called Trans Isomers.

⇒ Constitutional Isomer Example

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⇑ Introduction to Molecules

⇑⇑ Molecule FAQ