Aromatic peri-condensed system

The value of ring condensation index (3), ring compactness (7), and the extent of condensation of unsubstituted aromatic clusters (4) all indicate a skeleton of a peri-condensed system in the aromatic portion of this asphaltene. 

Peri-condensed aromatic compounds compounds based on angular condensed aromatic hydrocarbon systems, e.g., phenanthrene, chrysene, picene, etc. 

Distributions of pyrolytic PAFls are characterized by the dominance of the non-alkylated species shown in Fig. 7.3. Particularly abundant are the highly peri-condensed compounds—such as pyrene, the benzopyrenes, benzo[gfe]perylene and coronene—that result from extensive angular fusion of benzenoid systems.The presence of such PAF1 distributions in the aromatic... 

There are also indications that coal may be a system of peri-condensed polymeric structures in contrast to the suggestion of coal being predominantly kata-condensed. The occurrence of anthracene in the thermal products of coal processing has, on many occasions, been cited as evidence for the predominantly condensed nature of the aromatic systems in coal. Be that as it may, and there is some degree of truth to this supposition, there is also the distinct possibility that such anthracene systems in the thermal products are, to a degree, thermal artifacts that are formed by various dehyrocyclization reactions. 

The aromatic ring systems within petroleum-derived asphaltene are much more condensed (Haru/Car = 0.3-0.5, which is peri) than those of coal-derived asphaltene (Haru/Car = 0.5-0.7, which is kata). 

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