R and S Configurations
1) Choose the molecule form the drop-down menu and click on "Select"
2) Select the molecule's configuration and click on "Check Answer"Page 1
Assign the priority order to the susbtituents on the asymmetric carbon according to the Cahn-Ingold-Prelog rules.
- For every substituent, look at the first atom linked to the asymmetric carbon: the atom having the highest atomic number has the highest priority
- If it is not possible to define all the priorities in this way, look at the second atom away form the double bond carbon atom, and so on, until a point of difference can be found.
- The atoms having multiple bonds are equivalents to the same number of atoms linked by single bonds.
Correct Orientation of the Molecule
Correct Orientation of the Molecule - 2
Orient the molecule with the lowest priority group (4) back, away from the observer.
Configuration Assignment - 3
Observe the sequence 1 ---> 2 ---> 3. If, in order to follow the correct order the rotation is:
1) clockwise, the configuration is R
2) counterclockwise, the configuration is S