User:Ol' Dirty Jedi/sandbox

Coming Soon - Stereogenic unit
A stereogenic unit (also known as a stereogenic element, stereoelement or stereogen), is group of connected atoms within a molecule that may be a source of stereoisomerism. A stereogenic unit is a more encompassing concept than the stereocenter.

The presence of a stereogenic unit enables a molecule to exhibit enantiomerism or diastereomerism, however the presence of a stereogenic unit does not necessarily imply chirality.

According to the IUPAC definition, three basic types of stereogenic units are recognized for molecular entities involving atoms having not more than four substituents:


 * A central atom surrounded by a group of distinguishable substituents (or ligands), such that the interchange of any two of the substituents leads to a stereoisomer.


 * A chain of four non-coplanar atoms (or rigid groups) in a stable conformation, with restricted rotation such that (an imaginary or real) rotation about the central bond leads to a stereoisomer.


 * A grouping of atoms consisting of a double bond and substituents which can exhibit cis-trans isomerism.