R And S enantiomers Example 2

The stereocenters of chiral compounds are labeled as R or S. The R for “right hand”, clockwise and L for “left hand”, anti-clockwise is used to name the enantiomers of a chiral compound. The priorities of the atoms directly connected to the stereocenters are given according to their atomic masses. If some of those atoms have the same mass, the next atom connected is concidred. Therefore bromine has the highest atomic mass and have the highest priority. Hydrogen has the lowest atomic mass and thus the it has the lowest priority as nr 4. The molecule with the lowest priority is places pionting away from the viewer. The molecule needs to be rotated. See the animation. There is two animations. At the bottom, it can be selected. In this case when following the movement of the green arrow, the movement is right handed, clockwise and it is thus R. It is important to view the molecule from the correct side to get the rotation direction correctly.