Ranking Priorities:Cahn-Ingold-Prelog Rules Rule 1:Considering the double-bond carbons separately, look at the two atoms directly attached to each and rank them according to atomic number Br>CI>O>N>C>H higher In this case,the higher priority groups are opposite: (E)-2-bromo-2-chloro-propene Br higher Ranking Priorities: Cahn-Ingold-Prelog Rules Rule 1: Considering the double-bond carbons separately, look at the two atoms directly attached to each and rank them according to atomic number Br > Cl > O > N > C > H In this case,the higher priority groups are opposite: (E )-2-bromo-2-chloro-propene