E Z CIS TRANS question

[SonhosDaVida]

Hey guys, so I am a bit confused on naming structures.... For E/Z and Cis/Trans, are they named such that you first look at one C of the double bond and determine which group has higher priority, and then look at the other C on the double Bond and see which group is higher priority to determine Cis/Trans and E/Z?

Also, what would this hand drawn figure below be called?

And why is this figure Z when it has both of the high priority groups on the same side of the double bond?

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[SweetBurger]

Z places both highest priority groups on the same side of the double bond. Priority is given by molar mass (with more elaborate details when you get groups which branch). The top drawn figure is Z as the Br and Methyl group are on the same side of the double bond.

Generally E Z notation overrides cis trans notation, as cis trans notation falls short in naming certain structures.

 

[esob]

Go to the bottom of the page and read why here: Alkene Nomenclature: Cis and Trans and E and Z — Master Organic Chemistry

tldr: cis/trans nomenclature doesn't hold up for alkenes if you lack two common substituents.

 

[BerkReviewTeach]

For your first structure (hand drawn), there is no E or Z, because the right carbon has two hydrogens. It is 2-bromo-prop-2-enaldhyde, with no chiral designation.

For the second example, taken from Figure 2-14 on page 94 of the Berkeley Review Organic Chemistry book 1, consider the double bon carbons. The left carbon of the double bond has a CH3 group and a CH=O group. The CH=O group gets higher priority, because O outweighs H. The right carbon of the double bond has a CH3 group and an H. The CH3 group gets higher priority, because C outweighs H. The CH=O group on the left carbon is above the double bond and the CH3 group on the right carbon is also above the double bond. The highest priority groups on each carbon are both above the double bond, meaning they are on the 'zame' (same) side, so they are 'zis' (cis) to one another.

Zame zide iz zis!