Chiral molecules II R or S

Background Colour:

Consider this hypothetical molecule. Assign the priorities, rotate into the correct orientation and decide if it is R or S.

Step 1
Assign the atoms numbers 1 to 4 based on highest atomic number. In this example chlorine has the highest atomic number and is assigned 1 whereas hydrogen has the lowest atomic number and is assigned 4
Step 2
Arrange the molecule so that the lowest priority substituent faces backwards in this case number 4
Step 3
Mentally move from substituent 1 to 2 to 3. If you are moving clockwise assign the label R. If anticlockwise assign the label S


R as clockwise

Next Example

Back to previous page