see Instructions below

JME Editor courtesy of Peter Ertl, Novartis

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Useful Commands in JSmol:

1) ALT + mouse drag --> rotate on the screen x y plane

2) CTRL+ ALT + drag mouse --> move horizontally / vertically on the screen x y plane

3) using mouse wheel --> increase / reduce zoom

4) mouse --> rotate in the three dimensions

Background Color

Choose the Priority

Choose: R / S?

Check your Answer

Mostra tutti i Carboni Chirali

Instructions and Rules:

1) to assign priority, click on"Initialize".

2) click on the chiral carbon in JSMol and after click on "Chiral Carbon" button

3) repeat the step 2 for each atom directly linked to the Chiral Carbon to assign CIP Priority

4) orientate the molecule properly, with the priority 4 group point away from you

5) assign the chirality, R or S, by clicking on the chiral carbon and after on the proper "R" or "S" button

6) check your answer by clicking on the "Check Chirality" button

  • Enantiomers

  • Sequence Rules

    Sequence Rules



    Assign the priority order to the susbtituents on the asymmetric carbon according to the Cahn-Ingold-Prelog rules.


    1. For every substituent, look at the first atom linked to the asymmetric carbon: the atom having the highest atomic number has the highest priority
    2. 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.
    3. 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

    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