Introduction polycyclic aromatic hydrocarbon

Epoxides are often encountered in nature, both as intermediates in key biosynthetic pathways and as secondary metabolites. The selective epoxidation of squa-lene, resulting in 2,3-squalene oxide, for example, is the prelude to the remarkable olefin oligomerization cascade that creates the steroid nucleus [7]. Tetrahydrodiols, the ultimate products of metabolism of polycyclic aromatic hydrocarbons, bind to the nucleic acids of mammalian cells and are implicated in carcinogenesis [8], In organic synthesis, epoxides are invaluable building blocks for introduction of diverse functionality into the hydrocarbon backbone in a 1,2-fashion. It is therefore not surprising that chemistry of epoxides has received much attention [9]. 

Oxidation is intimately linked to the activation of polycyclic aromatic hydrocarbons (PAH) to carcinogens (1-3). Oxidation of PAH in animals and man is enzyme-catalyzed and is a response to the introduction of foreign compounds into the cellular environment. The most intensively studied enzyme of PAH oxidation is cytochrome P-450, which is a mixed-function oxidase that receives its electrons from NADPH via a one or two component electron transport chain (10. Some forms of this enzyme play a major role in systemic metabolism of PAH (4 ). However, there are numerous examples of carcinogens that require metabolic activation, including PAH, that induce cancer in tissues with low mixed-function oxidase activity ( 5). In order to comprehensively evaluate the metabolic activation of PAH, one must consider all cellular pathways for their oxidative activation. 

Polycyclic aromatic hydrocarbon carcinogenesis an introduction. Pages 1-17 in R.D. Harvey (ed.). 

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. 

Prahl, F.G., E. Crecelius, and R. Carpenter. 1984. Polycyclic aromatic hydrocarbons in Washington coastal sediments an evaluation of atmospheric and riverine routes of introduction. Environ. Sci. Technol. 18 687-693. 

Mobile phases are usually binary or ternary mixtures of solvents. Selectivity is affected mostly by mobile phase composition rather than strength, and peak shape and retention are both influenced by the addition of organic modifiers.101 Some compounds naturally have 77-donor or 77-acceptor groups and can be resolved directly. In many cases, however, introduction of 77-donating groups by derivatization steps is necessary. Figure 2.20 shows the proposed three-point interaction of 3-aminobenzo[a]pyrene, a polycyclic aromatic hydrocarbon (PAH), with a Pirkle-type stationary phase.111 Two possible interactions are illustrated, showing the best orientations for maximum interaction. 

The DLLME technique was introduced by Rezaee et al. and applied for extraction of polycyclic aromatic hydrocarbons (PAHs), pesticides, and alkylbenzenes [17] UV filters [18] and chlorophenols [19] from water samples. Summarized applications can be found in review articles [20-24]. An interesting concept is the introduction of ionic liquids as extractants [25-28]. 

Dipple, A. (1985) Polycyclic aromatic hydrocarbons an introduction, in Polycyclic Hydrocarbons and Carcinogenesis (ed. R.G. Harvey), ACS Symposium Series 283, American Chemical Society, Washington, DC, pp. 1-17. 

The measurements mentioned in the introduction were made at a large number of stations. In the course of the years aselection was made,and only stations representing a well described area were kept in operation. At all stations the following polycyclic aromatic hydrocarbons were determined ... 

The extractible fraction itself contains hundreds of compounds, and only a limited number can be routinely analysed. Among these molecules, the family of polycyclic aromatic hydrocarbons has been by far the most extensively studied, in terms of mechanism and properties. PAH are indeed quite easily produced in laboratory flames and can be routinely analysed, at least for molecdles with masses lower than 300 a.m.u. During the workshop, several papers have discussed in detail the analysis of polycyclic organic matter. However, as a brief introduction, it is useful to define the different compounds considered. 

Aromaticity (interpreted or defined in different ways) is a classical property which has been attributed to certain organic compounds. Indeed, the benzenoid hydrocarbons which exist chemically, are frequently referred to as polycyclic aromatic hydrocarbons (PAHs). Also kekulene is a typical PAH. Balaban (1980) asked the rhetorical question " Is aromaticity outmoded In his treatise an extensive historical introduction (going back to 1608) is found. The question is of course answered in the negative. A modern treatment of aromaticity can hardly avoid reference to Clar (1972). 

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. 

CONTENTS List of Contributors. Introduction to the Series An Editor s Forward, Albert Padwa. Preface, Randolph P. Thummel. Cyclooctatetraenes Conformational and ii-Elec-tronic Dynamics Within Polyolefinic [8] Annulene Frameworks, Leo A. Paquette. A Compilation and Analysis of Structural Data of Distorted Bridgehead Olefins and Amides, Timothy G. Lease and Kenneth J. Shea. Nonplanarity and Aromaticity in Polycyclic Benzenoid Hydrocarbons, William C. Herndon and Paul C. Nowak. The Dewar Furan Story, Ronald N. Warrener. Author Index. Subject Index. 

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