Sequence Rules

Assign the priority order to the susbtituents on the asymmetric carbon according to the Cahn-Ingold-Prelog rules.

1. For every substituent, look at the first atom linked to the asymmetric carbon: the atom having the highest atomic number has the highest priority
2. If it is not possible to define all the priorities in this way, look at the second atom away form the double bond carbon atom, and so on, until a point of difference can be found.
3. The atoms having multiple bonds are equivalents to the same number of atoms linked by single bonds.

Configuration Assignment

Observe the two carbon of the double bond separately. Look at the substituents on each carbon atom.

Consider the relative priority between the two substituents on each double bond carbon atom, following the Cahn-Ingold-Prelog rules.

If the groups having the highest priority for each double bond carbon atom are placed on the same side the configuration is Z (Zusammen, "together")

If the groups having the highest priority for each double bond carbon atom are placed on opposite sides the configuration is E (Entgegen, "opposite")