Polycyclic Aromatic Hydrocarbons, Five-Ring Compounds

POLYCYCLIC AROMATIC HYDROCARBONS, FIVE-RING COMPOUNDS 

T0241 Elf Atochem North America, Inc., INIPOL EAP-22 Microemulsion 

T0242 ELI Eco Logic International, Inc., Gas-Phase Chemical Reduction (GPCR) 

T0282 Environmental Soil Management, Inc., Low-Temperature Thermal Desorption 

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Polycyclic Aromatic Hydrocarbons, Five-Ring Compounds Benzo(a)pyrene Dibenzo(a )anthracene... 

Benzo(a)anthracene under Polycyclic Aromatic Hydrocarbons, Four-Ring Compounds Benzo(a)pyrene under Polycyclic Aromatic Hydrocarbons, Five-Ring Compounds Benzo(fc)fluoranthene under Polycyclic Hydrocarbons, Nonaltemant Compounds with Five Fused Rings... 

Polycyclic aromatic compound Polycyclic aromatic hydrocarbon Polycyclic aromatic sulfur heterocycle Polycyclic aromatic oxygen heterocycle Nitrogen-containing polycyclic aromatic compound (both heterocyclic and nonheterocyclic compounds) Secondary-nitrogen polycyclic aromatic nitrogen heterocycles (nitrogen in a five-membered ring)... 

Benzene (1) is the simplest aromatic hydrocarbon upon which our knowledge of aromatic chemistry is based. This hydrocarbon, the alkylbenzenes (2), the arylmethanes [e.g. diphenylmethane (3)], the biphenyls [e.g. biphenyl (4)] and the condensed polycyclic systems [e.g. naphthalene (5) and anthracene (6)] all exhibit chemical reactivity and spectroscopic features which are markedly different from their aliphatic and alicyclic hydrocarbon counterparts. Indeed the term aromatic character was introduced to specify the chemistry of this group of hydrocarbons and their substituted functional derivatives, and it was soon used to summarise the properties of certain groups of heterocyclic compounds having five- and six-membered ring systems and the associated condensed polycyclic analogues (Chapter 8). 

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. 

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