Molecular Topology and Molecular Properties I. »Sequence« Labels of Cata-Condensed Benzenoid Hydrocarbons Containing up to Five Rings

An algorithm ds described for the systematic numbering o,f benz,enoid hydrocarbons. The sum of decimal contributions of all vertices (carbon atoms) in th.e molecular graph is called the hydrocarbon label, L. These labels, which are based on pua:ely structural elements order a set o{ isomeric benzenoid hydrocarbons according to their properties including resonance and total pi-energies, ionization potent~als, heats of atomization, energies of lowest vacant and lo·west filled molecular orbitals and polarographic haLf-wave reduction potentials. Such hydrocarbon labels might easily be computed without resort to a computer