Configurational stereoisomers of the kind shown above need an additional nomenclature prefix added to the IUPAC name, in order to specify the spatial orientations of the groups attached to the double ...Configurational stereoisomers of the kind shown above need an additional nomenclature prefix added to the IUPAC name, in order to specify the spatial orientations of the groups attached to the double bond. Once the relative priorities of the two substituents on each of the double bond carbons has been determined, a cis orientation of the higher priority pair is designated Z, and a trans orientation is termed E.
