LewisJS can determine the configurations of trigonal (E/Z) and tetrahedral (R/S) stereocenters. Simply draw a structure and press the Get configurations button. (Because this application is intended for Lewis structures, it does not consider implicit H atoms when determining whether an atom is stereogenic, although one can easily imagine modifying the code to make it do so.)

LewisJS can also determine whether two Lewis structures are identical. Draw a structure, press the clipboard button, copy the source code, and paste it into the box below the drawing canvas. Then draw another structure, and see if it matches to the first one. (Currently, for two structures to match, stereocenter configurations and unshared electron configurations must match as well. Also, again, the application does not consider implicit H atoms.)

If you would like to use this code with or without modification, or if you find a bug, please contact Robert Grossman.