Aromatic hydrocarbons regions

An appreciation of the extent to which invertebrate species may be exposed to such chemicals comes from considering the effects of complex mixtures. In the North Atlantic ecosystem alone, hundreds of pollutant chemicals have been identified. These include metals, synthetic and chlorinated organics and polycyclic aromatic hydrocarbons. Over 300 aromatic hydrocarbons have been detected in some regions of the Chesapeake Bay, and high concentrations of PCBs have been... 

Another application of SFC-GC was for the isolation of chrysene, a poly aromatic hydrocarbon, from a complex liquid hydrocarbon industrial sample (24). A 5 p.m octadecyl column (200 cm X 4.6 mm i.d.) was used for the preseparation, followed by GC analysis on an SE-54 column (25 m X 0.2 mm i.d., 0.33 p.m film thickness). The direct analysis of whole samples transferred from the supercritical fluid chromatograph and selective and multi-heart-cutting of a particular region as it elutes from the SFC system was demonstrated. The heart-cutting technique allows the possibility of separating a trace component from a complex mixture (Figure 12.21). 

Methods for the synthesis of the biologically active dihydrodiol and diol epoxide metabolites of both carcinogenic and noncarcinogenic polycyclic aromatic hydrocarbons are reviewed. Four general synthetic routes to the trans-dihydrodiol precursors of the bay region anti and syn diol epoxide derivatives have been developed. Syntheses of the oxidized metabolites of the following hydrocarbons via these methods are described benzo(a)pyrene, benz(a)anthracene, benzo-(e)pyrene, dibenz(a,h)anthracene, triphenylene, phen-anthrene, anthracene, chrysene, benzo(c)phenanthrene, dibenzo(a,i)pyrene, dibenzo(a,h)pyrene, 7-methyl-benz(a)anthracene, 7,12-dimethylbenz(a)anthracene, 3-methylcholanthrene, 5-methylchrysene, fluoranthene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)-fluoranthene, and dibenzo(a,e)fluoranthene. 

The Bay Region Theory of Polycyclic Aromatic Hydrocarbon Carcinogenesis... 

Boehm, P.D. and J.W. Farrington. 1984. Aspects of the polycyclic aromatic hydrocarbon geochemistry of recent sediments in the Georges Bank region. Environ. Sci. Technol. 18 840-845. 

Smith, J.D., J.Y. Hauser, and J. Bagg. 1985. Polycyclic aromatic hydrocarbons in sediments of the Great Barrier Reef region, Australia. Mar. Pollut. Bull. 16 110-114. 

Yan, L.S. 1985. Study of the carcinogenic mechanism for polycyclic aromatic hydrocarbons — extended bay region theory and its quantitative model. Carcinogenesis 6 1-6. 

Fig. 10.12. Upper part The K, M, bay, and fjord regions of three isomeric tetracyclic aromatic hydrocarbons (benz[a]anthracene (BaA, 10.31), chrysene (CR, 10.32), and benzo[c]phenanthrene (BcPh, 10.33)). Lower part. The three pairs of enantiomeric (S,R)- and (R,S)-K-region epoxides and...

M. Shou, F. J. Gonzalez, H. V. Gelboin, Stereoselective Epoxidation and Hydration at the K-Region of Polycyclic Aromatic Hydrocarbons by cDNA-Expressed Cytochromes P450 1A1, 1A2, and Epoxide Hydrolase , Biochemistry 1996, 35, 15807 - 15813. 

Anodic oxidation in inert solvents is the most widespread method of cation-radical preparation, with the aim of investigating their stability and electron structure. However, saturated hydrocarbons cannot be oxidized in an accessible potential region. There is one exception for molecules with the weakened C—H bond, but this does not pertain to the cation-radical problem. Anodic oxidation of unsaturated hydrocarbons proceeds more easily. As usual, this oxidation is assumed to be a process including one-electron detachment from the n system with the cation-radical formation. This is the very first step of this oxidation. Certainly, the cation-radical formed is not inevitably stable. Under anodic reaction conditions, it can expel the second electron and give rise to a dication or lose a proton and form a neutral (free) radical. The latter can be either stable or complete its life at the expense of dimerization, fragmentation, etc. Nevertheless, electrochemical oxidation of aromatic hydrocarbons leads to cation-radicals, the nature of which is reliably established (Mann and Barnes 1970 Chapter 3). 

In summary, the distinctiveness of this soft ionization technique is that source optimization can be achieved through an independent adaptation of the ionization region, the electrical field gradient, and the gas flow. It is well suited for aromatic hydrocarbons that are selectively ionized, including nonpolar species, such as PAH, yielding to the lowest detection limits by orders of magnitude, as compared to all other API methods. 

Because of such difficulties as the featureless absorption and emission spectra in the vacuum ultraviolet region, very weak and energy-dependent fluorescence intensity, short excited-state lifetime, etc. the photophysics and photochemistry of alkanes is much less known than those of other organic molecules, for instance, aromatic hydrocarbons. In this chapter, the present status was reviewed. 

More recently, charge-transfer emission was anticipated when solutions of hydrocarbon anion radical salts in dimethoxyethane were mixed with Wurster s blue perchlorate.15 Emission was seen in every instance however, with eight anion radicals derived from 3 to 5 ring-fused aromatic hydrocarbons, the emission was derived from the hydrocarbon rather than the complex. Preliminary studies with smaller hydrocarbons, biphenyl and naphthalene, did show emission in the region (18 kK) where charge transfer was expected. The question as to what pairs of ion radicals will be emissive under what conditions has only begun to be considered. Much opportunity for further experimentation exists in this area. 

Bodzek, D K. Luks-Betlej, and L. Warzecha, Determination of Particle-Associated Polycyclic Aromatic Hydrocarbons in Ambient Air Samples from the Upper Silesia Region of Poland, Atmos. Environ., 27A, 759-764 (1993). 

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