Cis and Trans, E and Z Nomenclature

Since double bonds and rings can’t rotate, we need different names for the different arrangements they can create. 

Two groups coming off the same carbon never have a cis/trans relationship. In case you are wondering, they are called geminal (you don’t need to know this yet.) 

E/Z Nomenclature

The cis/trans nomenclature system is awesome, but it breaks down with multisubstituted alkenes. 

So the E/Z naming system allows us to name tri- and tetra- substituted alkenes.

The difference between E and Z

Using the periodic table to assign priorities, trans = E, and cis = Z. 

Example: Assign an (E) – (Z) designation to the following alkenes if applicable

2m

Great! Now let’s combine this with what we’ve learned about functional groups (alkyl halides and alcohols) to name some more complex molecules. 

Problem: Determine the IUPAC name of the following molecule 

4m

This was a great example of how the root chain must always have the functional group within it, even if it is shorter!

Problem: Determine the IUPAC name of the following molecule 

7m

Hope you don’t hate me for throwing two alcohols in there! This is great practice though.