E,Z System

The E,Z system is used to assign the configuration of a highly-substituted alkene as follows:

1. The relative priorities of the two groups attached to each of the sp2 carbons of the double bond are assigned as per the rules in Table 9.1.
2. If the high priority groups are on the same side of the double bond, the isomer is allocated the Z configuration, and if they are on opposite sides of the double bond, the configuration is designated as E.

Table 9.1