cis vs trans alkenes

Geometric Isomers

The E/Z naming system

E -entgegen, opposite sides Z - zusammen, together on the same side

Ranking Priorities: Cahn-Ingold-Prelog Rules

Must rank atoms that are connected at comparison point

Higher atomic number gets higher priority

Br > Cl > O > N > C > H

In this case, the higher priority groups are opposite: (E )-2-bromo-2-chloro-propene

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If atomic numbers are the same, compare the next connection point at same distance

Compare until you get the higher atomic number

Extended Comparison

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Dealing With Multiple Bonds