Rank the following groups in order of decreasing priority according to the Cahn-Ingold-Prelog system.
A)I III IV II
B)III IV I II
C)IV III I II
D)IV I III II

Question

Rank the following groups in order of decreasing priority according to the Cahn-Ingold-Prelog system. 
A)I > III > IV > II 
B)III > IV > I > II 
C)IV > III > I > II 
D)IV > I > III > II

Quizplus · Accepted Answer

According to the Cahn-Ingold-Prelog system, the priority of groups is determined by the atomic number of the atoms directly attached to the stereocenter. In this case, group IV is attached to a carbon with a double bond to another carbon (double bond has priority over single bond), which is attached to group III which is attached to group II, and group I is attached to the same carbon as group III. Therefore, the order of decreasing priority is IV > III > I > II, which corresponds to choice C.

Rank the Following Groups in Order of Decreasing Priority According