Electron and energy content of hexagons in benzenoid hydrocarbons

Abstract

In this paper we first define the recently proposed (by Randić and Balaban, in 2004) π-electron content (EC) of hexagons in benzenoid hydrocarbons. In full analogy to it one may conceive also the π-electron energy content (ec) of hexagons. These contents are mutually related, but in a somewhat perplexed manner. We establish the actual relation between EC and ec in the case of catacondensed benzenoid hydrocarbons. In catacondensed benzenoid systems there are only four types of hexagons: terminal, linearly annelated, angularly annelated, and branched. We show that within hexagons of the same type the relation between ec and EC is nearly linear and the respective regression lines are nearly parallel and equidistant. The analogous relations between EC and ec in pericondensed benzenoids are essentially the same, yet significantly more complicated because in pericondensed benzenoids there exist 12 distinct annelation modes of hexagons.