Electron content of rings of fully benzenoid hydrocarbons

: The distribution of -electrons in rings of fully benzenoid hydrocarbonswas investigated. It was found that the electron content EC of “full” rings varies sig-nificantly (between 5.5 and 2.5 electrons), and depends on the annelation mode,mainly on the number of adjacent rings. “Full” rings belonging to the same annela-tion class have nearly equal EC -values. The EC -values of all “empty” rings are alsonearly equal (around 2 electrons). Keywords : fully benzenoid hydrocarbons, -electron content of ring, “full” rings,“empty” rings.INTRODUCTION The use of Kekule structural formulas in the analysis of the -electron struc-tureofbenzenoidhydrocarbonsdatesbacktothe1930s,andsincethenhasbecomeone of the standard methods of the theoretical chemistry of conjugated mole-cules. 1,2 It is therefore somewhat surprising that the idea of assessing the distribu-tion of -electrons into rings by means of Kelule structures was put forward onlyquite recently. 3,4 According to the proposed method,