Question

What are the rules for defining E-Z configuration?

Answer 1

Consider two alkenes,

This is very reminiscent of the `R` and `S` configuration assignments. We find an double bond that has a few different substituents, such as those above.

In the former molecule, it's `Z` since the highest priority substituents are on the same side of double bond.

In the latter molecules, it's `E` since the highest priority substituents are on different sides of the double bond.

It's very straightforward compared when you first learned absolute configuration!