This drill requires the latest version of the Java platform.  You can get this (free download) by following the link at the bottom of the page.

This drill tests one's ability to interpret a Fischer projection and to determine the chiral center's absolute stereochemistry.  You can use the buttons R and S to submit your answer or you can use the mouse (LMB for S, RMB for R)  In number mode (indicated by button with the '#'), the program will tell you the priorities of the substituents.  In atom mode (the button with the 'A'), you must determine the priorities yourself.  If you are having trouble determining priorities, you might want to try the following drill :

Cahn-Ingold-Prelog Drill

Remember, in a Fischer projection, the vertical substituents are going into the page and the horizontal substituents are coming out of the page.

This program determines the relative priorities of the substituents "on site", ie the priorities are not determined by us beforehand but rather by an algorithm "live".  While we have not yet seen it happen, there is always a chance that the algorithm may be flawed.  Use this knowledge at your own risk. 

If you do see any errors, inaccuracies, or bugs, please notify us immediately via feedback.  Also let us know if the program appears awkward on your machine, fonts are too big or small, etc.


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