cis-trans isomers

https://doi.org/10.1351/goldbook.C01093
@S05983@ @O04281@ or @C01497@ (or hetero-analogues) which differ in the positions of atoms (or groups) relative to a reference plane: in the cis-@I03289@ the atoms are on the same side, in the @C01092@-@I03289@ they are on opposite sides.
C01093.png
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2204 [Terms] [Paper]