Graph theoretical descriptors of two-dimensional chirality with possible extension to three-dimensional chirality.

We report on construction of a graph theoretical descriptor of chirality for two-dimensional benzenoid hydrocarbons. For achiral molecules the index is zero, while for chiral molecules it takes a positive or negative value for a molecule and one for its mirror image. Hence, we also have obtained a descriptor that measures chirality on an absolute scale, i.e., it assigns to a molecule a positive (or a negative) value without ever requiring information on the enantiomer of the molecule considered or any other pair of standards. In addition, we have briefly outlined how this is the 2-D approach extended to characterization of chiral objects in 3-D space, at least in the case of n-alkane rotamers.