Editing Cahn–Ingold–Prelog priority rules (section)

==== Double bonds: ''E''/''Z'' ====
{{Main article|E-Z notation}}

For double bonded molecules, Cahn–Ingold–Prelog priority rules (CIP rules) are followed to determine the priority of substituents of the double bond. If both of the high priority groups are on the same side of the double bond ([[Cis-trans isomerism|''cis'' configuration]]), then the [[stereoisomer]] is assigned the configuration ''Z'' (''zusammen,'' [[German language|German]] word meaning "together").  If the high priority groups are on opposite sides of the double bond ([[Cis-trans isomerism|''trans'' configuration]]), then the stereoisomer is assigned the configuration ''E'' (''entgegen'', German word meaning "opposed")<ref>{{Cite book |last=International Union of Pure and Applied Chemistry. Commission on the Nomenclature of Organic Chemistry |url=https://www.worldcat.org/oclc/27431284 |title=A guide to IUPAC nomenclature of organic compounds : recommendations 1993 |date=1993 |publisher=Blackwell Scientific Publications |others=Robert Panico, Warren H. Powell, Jean-Claude Richer |isbn=0-632-03702-4 |location=Oxford |oclc=27431284}}</ref>