Preferred Label : cis, trans;
IUPAC definition : Descriptors which show the relationship between two ligands attached to separate atoms
that are connected by a double bond or are contained in a ring. The two ligands are
said to be located i cis /i to each other if they lie on the same side of a plane.
If they are on opposite sides, their relative position is described as i trans /i
. The appropriate reference plane of a double bond is perpendicular to that of the
relevant σ-bonds and passes through the double bond. For a ring (the ring being in
a conformation, real or assumed, without re-entrant angles at the two substituted
atoms) it is the mean plane of the ring(s). For alkenes the terms i cis /i and
i trans /i may be ambiguous and have therefore largely been replaced by the em E,
Z /em convention for the nomenclature of organic compounds. If there are more than
two entities attached to the ring the use of i cis /i and i trans /i requires
the definition of a reference substituent.;
Origin ID : C01092;
See also
Descriptors which show the relationship between two ligands attached to separate atoms
that are connected by a double bond or are contained in a ring. The two ligands are
said to be located i cis /i to each other if they lie on the same side of a plane.
If they are on opposite sides, their relative position is described as i trans /i
. The appropriate reference plane of a double bond is perpendicular to that of the
relevant σ-bonds and passes through the double bond. For a ring (the ring being in
a conformation, real or assumed, without re-entrant angles at the two substituted
atoms) it is the mean plane of the ring(s). For alkenes the terms i cis /i and
i trans /i may be ambiguous and have therefore largely been replaced by the em E,
Z /em convention for the nomenclature of organic compounds. If there are more than
two entities attached to the ring the use of i cis /i and i trans /i requires
the definition of a reference substituent.
