Chart of Definitions and Interrelationships of the Different Kinds of Isomers

Isomers may be:

• Skeletal (structural) isomers, which have different atom-to-atom connections.

• Stereoisomers, which have the same atom-to-atom connections, but nonsuperimposable shapes. Stereoisomers may be:

  • Diastereomers, which have different internal dimensions (distances between nonbonded atoms, dihedral angles, etc.), and are not mirror images; or,
  • Enantiomers, which have identical internal dimensions, and are nonsuperimposable mirror images.

  Stereoisomers may also be:

  • Configurational stereoisomers, which can be interconverted only by breaking σ or π bonds, or by changing the configurations of stereocenters; or,
  • Conformational stereoisomers, which can be interconverted by rotation about σ bonds (including chair flips) or by lone pair inversion.

Stereoisomers	interconversion requires changing the configurations of stereocenters	can be interconverted by rotation about σ bonds or by lone pair inversion
different internal dimensions	configurational diastereomers (cis/trans, E/Z)	conformational diastereomers (staggered/eclipsed, anti/gauche, axial/equatorial)
nonsuperimposable mirror images	configurational enantiomers	conformational enantiomers

Note: The terms 'diastereomer' and 'enantiomer' refer to 'configurational diastereomer' and 'configurational enantiomer' unless otherwise specified.

You might want to look at a flow chart showing how to determine the isomeric relationship between two structures.

Or you might want to look at some examples of the different kinds of stereoisomers.

Or you might find it useful to see a glossary of stereochemical terms.