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Alkenes in nature
Systems for Designating Alkene
Diastereomers
1. cis and trans system: to designate the stereochemistry of alkene
diastereomers (cis–trans isomers).
• These terms are only applied to disubstituted alkenes. Cis–trans
stereoisomerism in alkenes is not possible when one of the doubly
bonded carbons bears two identical substituents.
• If the alkene is trisubstituted or tetrasubstituted, the terms cis and
trans do not apply at all.
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