E,Z Convention

E,Z Convention is a method used to specify relative configuration at carbon atoms in alkene groups.  According to E,Z convention, if the pair of carbon atoms in an alkene group could exist in two relative configurations, one is designated using the label E and the other the label Z.

eg:



To determine whether an alkene group is E or Z, use the following two-step procedure.

Step 1:
Assign priority numbers to the two ligands on each carbon atom in the alkene group.  (See R,S convention for the procedure.)

eg. 1:



eg. 2:



Step 2:



eg. 1:



eg. 2:



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