Resonance energy of giant benzenoid hydrocarbon C78H26

Abstract

We calculated the molecular resonance energy for a recently synthesized giant benzenoid hydrocarbon C78H26 having 27 fused benzene rings. Using the method of conjugated circuits, we derived the expression for the molecular resonance energy (RE) in terms of contributing conjugated circuits of size 6, 10, and 14. The method of conjugated circuits makes it possible to express the qualitative method of Clar into a quantitative form by deriving the contributions to RE of the individual benzene rings of a molecule. The results support the π-sextet model of Clar in which the contributions to the molecular resonance energy of rings depends on the assignment of π-sextets to a selection of individual benzene rings. The ring RE is sensitive to the immediate geometrical environment of the individual benzene rings which allows classification of benzene rings according to their relative contributions to the molecular RE. Such classification facilitates the calculation of reasonably accurate RE for even larger systems built from fused benzene rings. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 697–708, 1999