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Narrative
Orient the molecule so that you are looking down the bond from the chiral carbon atom to the lowest priority group. Counterclockwise orientation of the three visible substituents gives the S- configuration. Clockwise orientation gives the R- configuration.

Discussion
The assignment of R- and S- configurations of chiral carbon atoms is demonstrated. The four substituents about a chiral carbon atom are assigned priority according to increasing atomic number. The molecule is oriented so that the observer looks down the bond from the chiral carbon atom to the lowest priority group (4). If the other three groups are arranged clockwise from highest (1) to lowest priority (3), the configuration is R-. If the orientation is counterclockwise, the configuration is S-.