Preferred Label : stereogenic unit;
Detailed label : stereogenic unit (stereogen/stereoelement);
IUPAC definition : A grouping within a molecular entity that may be considered a focus of stereoisomerism.
At least one of these must be present in every enantiomer (though the presence of
stereogenic units does not conversely require the corresponding chemical species to
be chiral). Three basic types are recognized for molecular entities involving atoms
having not more than four substituents: br/ ol li A grouping of atoms consisting
of a central atom and distinguishable ligands, such that the interchange of any two
of the substituents leads to a stereoisomer. An asymmetric atom (chirality centre)
is the traditional example of this stereogenic unit. /li li A chain of four non-coplanar
atoms (or rigid groups) in a stable conformation, such that an imaginary or real (restricted)
rotation (with a change of sign of the torsion angle) about the central bond leads
to a stereoisomer. /li li A grouping of atoms consisting of a double bond with
substituents which give rise to cis-trans isomerism. /li /ol ;
Origin ID : S05980;
See also
A grouping within a molecular entity that may be considered a focus of stereoisomerism.
At least one of these must be present in every enantiomer (though the presence of
stereogenic units does not conversely require the corresponding chemical species to
be chiral). Three basic types are recognized for molecular entities involving atoms
having not more than four substituents: br/ ol li A grouping of atoms consisting
of a central atom and distinguishable ligands, such that the interchange of any two
of the substituents leads to a stereoisomer. An asymmetric atom (chirality centre)
is the traditional example of this stereogenic unit. /li li A chain of four non-coplanar
atoms (or rigid groups) in a stable conformation, such that an imaginary or real (restricted)
rotation (with a change of sign of the torsion angle) about the central bond leads
to a stereoisomer. /li li A grouping of atoms consisting of a double bond with
substituents which give rise to cis-trans isomerism. /li /ol
