One of the subjects of special interest in chemical structure handling is to be able
to associate a unique quantitative value to each and every chemical compound. The job is
not only huge from the stand point of the number of compounds known and to be known,
but quite difficult as well from the angle of developing a suitable method. One of the
common situations is to be able to discriminate isomeric structures where a large number of
compounds having closely related structures for same number of atoms come into picture
and this number grows very fast as the number of atoms increases. Getting quantitative
descriptors having power of discriminating one compound from another is an important
requirement for storage, retrieval and handling of chemical structures as well as for
predicting molecular properties/activities. In this chapter, we review several molecular
descriptors, mostly topological distance based, in the form of topological indices
considering the connectivity aspect of molecular structures only, that have useful
discriminative power.
Keywords: Chemical documentation, discrimination of graphs, distance based
topological index, distance sum, graph distance complexity, graph vertex
complexity, information content of a graph, information-theoretical topological
index, molecular connectivity, molecular graph, paths in a graph, spectra of graph,
structure property/activity analysis, topological distance, topological index.
