Hydrocarbon, Polycyclic aromatic

Dehydrogenation (the conversion of alicycllc or hydroaroraatic compounds into their aromatic counterparts by removal of hydrogen and also, in some cases, of other atoms or groups) finds wide appUcation in the determination of structure of natural products of complex hydroaroraatic structure. Dehydrogenation is employed also for the synthesis of polycyclic hydrocarbons and their derivatives from the readily accessible synthetic hydroaroraatic compounds. A very simple example is the formation of p-raethylnaphthalene from a-tetra-lone (which is itself prepared from benzene—see Section IV,143) ... 

For books on this subject, see Gutman, I. Cyvin, S.J. Introduction to the Theory of Benzenoid Hydrocarbons, Springer NY, 1989, Dias, J.R. Handbook of Polycyclic Hydrocarbons, Part A Benzenoid Hydrocarbons, Elsevier NY, 1987, Clar, E. Polycyclic Hydrocarbons, 2 vols. Academic Press NY, 1964. For a periodic table that systematizes fused aromatic hydrocarbons, see Dias, J.R. Acc. Chem. Res., 1985, 18, 241 Top. Curr. Chem., 1990, 253, 123 J. Phys. Org. Chem., 1990, 3, 765. 

Although the aromatic polycyclic hydrocarbons are usually associated with tar and soot formation, in a firing or roasting process, compounds such as fluoranthrene and pyrene have also been found in green... 

Morgante, A., Aromatic polycyclic hydrocarbons in coffee, Riv. Merceol., 19, 215, 1980. (CA94 173070s)... 

Man has served as the unintentional guinea pig for the identification of some major classes of carcinogens. These include the polycyclic aromatic hydrocarbons (PAH), or polyarenes, which have been identified as the active components of soot, which was recognized by the London surgeon Percivall Pott two centuries ago as responsible for cancer of the scrotum in chimney sweeps. Subsequently, polycyclic hydrocarbons have been implicated as agents responsible for skin cancer in other occupations such as shale oil distillation and mule spinning in the cotton industry. 

PGH synthase and the related enzyme lipoxygenase occupy a position at the interface of peroxidase chemistry and free radical chemistry and can clearly trigger metabolic activation by both mechanisms. The peroxidase pathway activates compounds such as diethylstilbestrol and aromatic amines whereas the free radical pathway activates polycyclic hydrocarbons (59). Both pathways require synthesis of hydroperoxide in order to trigger oxidation. 

De Voogt, P., Van Zijl, G.A., Covers, H., Brinkman, U.A.T. (1990) Reversed-phase TLC and structure-activity relationships of polycyclic (hetero) aromatic hydrocarbons. J. Planar Chromatog.-Mod. TLC 3, 24—33. 

Leoni [366] observed that in the extraction preconcentration of organochlo-rine insecticides and PCB s from surface and coastal waters in the presence of other pollutants such as oil, surface active substances, etc., the results obtained with an absorption column of Tenax-Celite are equivalent to those obtained with the continuous liquid-liquid extraction technique. For non-saline waters that contain solids in suspension that absorb pesticides, it may be necessary to filter the water before extraction with Tenax and then to extract the suspended solids separately. Analyses of river and estuarine sea waters, filtered before extraction, showed the effectiveness of Tenax, and the extracts obtained for pesticide analysis prove to be much less contaminated by interfering substances than corresponding extracts obtained by the liquid-liquid technique. Leoni et al. [365] showed that for the extraction of organic micro pollutants such as pesticides and aromatic polycyclic hydrocarbons from waters, the recoveries of these substances from unpolluted waters (mineral and potable waters) when added at the level of 1 xg/l averaged 90%. 

Hendriks, A.J., H. Pieters, and J. de Boer. 1998. Accumulation of metals, polycyclic (halogenated) aromatic hydrocarbons, and biocides in zebra mussel and eel from the Rhine and Meuse Rivers. Environ. Toxicol. Chem. 17 1885-1898. 

DiGiovanni, J. and T.J. Slaga. 1981b. Modification of polycyclic aromatic hydrocarbon carcinogenesis. Pages 259-292 in H.V. Gelboin and P.O. Ts o (eds.). Polycyclic Hydrocarbons and Cancer. Vol. 3. Academic Press, New York. 

Dipple, A. 1985. Polycyclic aromatic hydrocarbon carcinogenesis an introduction. Pages 1-17 in R.D. Harvey (ed.). Polycyclic Hydrocarbons and Carcinogenesis. ACS Symp. Ser. 283. Amer. Chem. Soc., Washington, D.C. 

Among polycyclic hydrocarbons, there is a considerable interest in poorly studied compounds having a benzopentalene skeleton. The presence of a fused aromatic ring is expected to restrict possible rearrangements, therefore ensuring relatively high regioselectivity. 

S. K. Yang, M. Mushtaq, P. L. Chiu, Stereoselective Metabolism and Activation of Polycyclic Aromatic Hydrocarbons , in Polycyclic Hydrocarbons and Carcinogenesis , Ed. R. G. Harvey, American Chemical Society, Washington, 1985, p. 19 - 34. 

There are indications that pure naphthalene (a constituent of mothballs, which are, by definition, toxic to moths) and alkylnaphthalenes are from three to 10 times more toxic to test animals than are benzene and alkylbenzenes. In addition, and because of the low water solubility of tricyclic and polycyclic (polynuclear) aromatic hydrocarbons (i.e., those aromatic hydrocarbons heavier than naphthalene), these compounds are generally present at very low concentrations in the water-soluble fraction of oil. Therefore, the results of this smdy and others conclude that the soluble aromatics of crude oil (such as benzene, toluene, ethylbenzene, xylenes, and naphthalenes) produce the majority of its toxic effects in the enviromnent. 

Polycyclic aromatic hydrocarbons Aromatic hydrocarbons composed of fused benzene rings. Many are highly carcinogenic. 

Certain industrial populations exposed to coal tar products have a demonstrated risk of skin cancer. Substances containing polycyclic hydrocarbons or polynuclear aromatics (PNAs), which may produce skin cancer, also produce contact dermatitis (e.g., coal tar pitch, cutting oils)." Although allergic dermatitis is readily induced by PNAs in guinea pigs, it only rarely is reported in humans from occupational contact with PNAs. Incidences in humans have resulted largely from the therapeutic use of coal tar preparations. ... 

Polycyclic Aromatic Hydrocarbons with Two or Three Fused Rings Polycyclic Aromatic Hydrocarbons PAH PNA POM Polycyclic Hydrocarbons, Nonalternant Compounds with Four Fused Rings Fluoranthene... 

---