Determining R/S Configuration

Determine R/S Configuration

1) Prioritize the 4 groups around the chiral carbon.

• Use the CIP System as discussed earlier.
• The structure below is CBrIClH.
• Since Iodine has the largest atomic number it gets the highest priority (1), while hydrogen get the lowest priority (4).

Show Priorities

2) Orient the molecule such that lowest priority group is facing away from you.

• Rotate the structure above such that the H atom is hidden behind the C atom.

3) Assign R/S based on remaining three substituents facing you.

• If remaining three substituents are clockwise its R configuration.
• If remaining three substituents are counter-clockwise its S configuration.
• The symbol R comes from the Latin rectus for right, and S from the sinister for left.
• Our example above is the S configuration.

What is the R/S configuration of the following structure?

How does this structure relate to the structure above?

Show Priorities