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 CIBrClH.
• Since Iodine has the largest atomic number it gets the highest priority (1), while hydrogen get the lowest priority (4).

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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?

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