Overview of Polycyclic Aromatic Compounds (PAC)

Achten C., Andersson J.

Abstract

The chemical group of polycyclic aromatic compounds (PAC), including the betterknownsubgroup of polycyclic aromatic hydrocarbons (PAH) and the heterocyclic aromaticcompounds (NSO-PAC, heterocycles), comprise several thousand individual compounds.It is hard to find a comprehensive overview in the literature of these PACsthat includes a substantial amount of relevant properties. Here an attempt is made tosummarize the most studied but also some less well-known PACs. In addition to basicdata such as recommended names, abbreviations, CAS numbers, molecular formulas,chemical structures, and exactmono-isotopic molecular weights, physico-chemical propertiestaken from the literature like boiling points, vapor pressures, water solubilities,Henry’s Law constants, n-octanol-water partition coefficients (log KOW), and pKa aresummarized. Selected toxicological data are listed indicating carcinogenic and mutagenicactivity or effects on different organisms.PAC nomenclature is a complex topic, so suggestions for practical use are made.Regarding available data, estimated (instead of measured) values should be used withcaution because considerable deviations from experimentally determined values canoccur. For an enhanced understanding of the behavior of single PACs in comparisonwith each other, some of the properties mentioned above are plotted vs. the number ofrings or the degree of alkylation. Also, some physico-chemical data are correlated withdifferent functional groups as substituents of the PAHs.This article reveals that rather little is known about the less common PACs, e.g.,higher molecular weight compounds, alkylated or otherwise substituted aromatics, forinstance, keto-, oxo-, amino-, nitro-, cyano-PAHs, or some heterocyclic aromatic compounds,including their derivatives. It mirrors the limited state of knowledge about thevariety of PACs that do not belong to the 16 EPA PAHs.