  Chirality is of primary importance in many areas of chemistry and has been
extensively investigated since its discovery. We introduce here the description
of central chirality for tetrahedral molecules using a geometrical approach
based on complex numbers. According to this representation, for a molecule
having n chiral centres, it is possible to define an index of chirality.
Consequently a chirality selection rule has been derived which allows the
characterization of a molecule as achiral, enantiomer or diastereoisomer.
