Condensed polycyclic benzenoid aromatic

Condensed polycyclic benzenoid aromatic hydrocarbons are customarily regarded as planar molecular structures because of the geometrical constraints of carbon atoms in a state of sp2 hybridization. A well-known exception is the class of compounds called the helicenes (18) for which the nonbonded overlap of two terminal benzenoid rings in a cata-condensed structure, as in structure 1, forces a molecule into a nonplanar helical structure. A second exceptional class of compounds is related to corannulene (2) and other an-nulenes of this type (19, 20). In corannulene, strain associated with the pericondensed five- and six-membered rings requires adoption of a bowlshaped structure (20, 21). For both structures 1 and 2 the aromatic character of the benzenoid rings is retained to an appreciable extent. 

Herndon WC (1990) On Enumeration and Classification of Condensed Polycyclic Benzenoid Aromatic Hydrocarbons. J Am Chem Soc 112 4546... 

Nomenclature of Benzenoid Cata-Condensed Polycyclic Aromatic Hydrocarbons. 

Balaban AT, Harary F (1968) Chemical Graphs — V - Enumeration and Proposed Nomenclature of Benzenoid Cuta-Condensed Polycyclic Aromatic Hydrocarbons. Tetrahedron 24 2505... 

A. T. Balaban and F. Harary, Chemical graphs V. Enumeration and proposed nomenclature of benzenoid cata-condensed polycyclic aromatic hydrocarbons. Tetrahedron 24 (1968) 2505-2516. 

Balaban, A.T. and Artemi, C. (1989). Chemical Graphs. Part 51. Enumeration of Nonbranched Catafusenes According to the Nmnbers of Benzenoid Rings in the Catafusene and Its Longest Linearly Condensed Portion. Polycyclic Aromatic Compounds, 1,171-189. 

Aromaticity. VIII). Resonance energies of cata-condensed benzenoid polycyclic hydrocarbons. Rev. Roum. Chim., 15, 1243—1250. 

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