1. Select the molecule by clicking on it;
  2. Select the molecule configuration and click on "Check Answer". At the bottom of the page there are instructions on how to assign the correct configuratiomn to the molecule.



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.