Novel graph-theoretical approach to estimating the relative importance of individual Kekulé valence structures. II. Benzenoid systems having four to seven fused benzene rings: “Pseudodegenerate” states

Kekulé structures of 10 nonlinear acenes comprising 83 graphs are studied through the use of connectivities M. Randi?, J. Am. Chem. Soc. 97 , 6609 (1975)] of their corresponding submolecules H. Joela, Theor. Chim. Acta 39 , 241 (1975)]. In certain rare cases states were identified to have identical branching indices but different Kekulé indices A. Graovac, I. Gutman, M. Randi?, and N. Trinajsti?, J. Am. Chem. Soc. 95 , 6267 (1973)]. Such states are termed pseudodegenerate states. A method is described to forecast and another to remedy such situations. The method emphasizes the relation between VB (resonance) and MO theories using graph-theoretical concepts.