Ken Tao is the MedSchoolCoach expert on MCAT, and helps you remember E-Z notation for double bonds by recalling that E is for Enemy (opposite sides) and Z is for Zame side (same side).
So as a quick review of how this works, let’s take a look at a couple example molecules we have here. You can see that they both have a double bond and there are three substituents. Two fluorine atoms and a methyl group.
So the way you assign E-Z notation is you want to focus on the two highest priority substituents on the two carbons in the double bond. So on this carbon, it’s going to be the fluorine, because fluorine has a greater atomic number than hydrogen.
On this other carbon, it’s also going to be fluorine because fluorine has a greater atomic number than carbon.
So now looking at this molecule you’ll notice that the two fluorine atoms, the two highest priority substituents are on opposite sides of the double bond. We would assign this molecule an E notation. E for opposite sides.
And the way you can remember this is by using the mnemonic E is for energy. So if you’re in a fight the enemy is going to be on the opposite side. So e molecules have the highest party groups on opposite sides of the double bond. Over here we have a similar molecule but now you can see that the two highest party groups the two flurries are on the same side of the double bond. This molecule is given the Z notation and the way you can remember this is the Z. As for Zane side so we essentially took the word same and just replace the S with a Z To help us remember this.
So remember if you have a Z molecule that’s because the two highest priority groups are on the same side.
All right. So that should help you keep track of easy notation for the MCAT.