E/Z Nomenclature of Alkenes

We are familiar with the cis and trans nomenclature for simple alkenes. However, this designation isn't enough when there are four different groups on the double bond.

We will use the E/Z system of nomenclature to identify these alkenes. It's easy! We will look at each atom directly attached to the carbons of the double bond and assign a priority according to atomic number. If the high-priority groups are on the same side, that will be Z from the German word zusammen, meaning together. If the high-priority groups are on opposite sides, that will be an E alkene for the German word entgegen, meaning opposite.

Check out the video below with several examples of how to apply the rules. We will do another practice problem or two in lecture. These rules will come back again when we determine R or S configuration of chiral centers on Friday.

For additional background and practice, please refer to Chapter 4.1-4.2 of the text and the problems within.

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