Polychlorinated dibenzodioxins isomers

Polychlorinated dibenzodioxins (PCDDs) Polychlorinated dibenzofurans (PCDFs) Polychlorinated biphenyls (PCBs) Polyaromatic hydrocarbons (PAHs) Pentachlorophenol Short chain chlorinated paraffins Hexachlorocyclohexane isomers Mercury and organic mercury compounds Cadmium... 

Polychlorinated hydrocarbons, such as polychlorinated dibenzodioxins, dibenzofurans, and biphenyls exist as a number of different congeners. Some of these are geometric isomers. Many cause a range of toxic effects that are believed to be mediated by interaction with the aryl hydrocarbon receptor (AhR) (they are known as pleiotropic effects). However, not all the isomers cause these effects because they do not all interact with the AhR receptor. To interact with this receptor, the molecule needs to be flat (planar). It can be seen in the diagram (Fig. 5.2)... 

Schecter A, Constable JD, Bangert JV, et al. 1989b. Isomer specific measurement of polychlorinated dibenzodioxin and dibenzofuran isomers in human blood from American Vietnam veterans two decades after exposure to Agent Orange. Chemosphere 18 531-538. 

Kuroki H, Haraguchi K, Masuda Y (1984), Chemosphere 13 561-573.. .Synthesis of polychlorinated dibenzofuran isomers and their gas chromatographic profiles44 Riehle U (1990), Analytik der polyhalogenierten (Brom/Chlor) Dibenzodioxine und Dibenzo-furane und deren thermische Bildung in einem Verbrennungsmotor44, Dissertation, Universitat Ulm... 

The chlorinated phenols, partieularly pentachlorophenol and the trichloro-phenol isomers, are signifieant hazardous wastes. These compounds are biocides that are used to treat wood to prevent rot by fungi and to prevent termite infestation. They are toxic, causing liver malfunction and dermatitis. However, contaminant polychlorinated dibenzodioxins ( dioxin ) may be responsible for some of the observed effects. Pentachlorophenol and other aromatic halides and aromatic hydrocarbons used as wood preservatives are encoimtered at many hazardous-waste sites in wastewaters and sludges. 

The phosphorescence spectra of chlorinated 1,4-dibenzodioxins, in hexane solutions at 77 and 4.2 K, have a well-resolved vibronic structure with distinctions in quasi-linear phosphorescence spectra even for closely related isomers of polychlorinated dioxins <1998MI129>. 

There are 75 possible isomers of polychlorinated-p-dibenzodioxin (PCDD) and 135 such isomers of polychlorinated dibenzofuran (PCDF). These related compounds are known as congeners. In addition, PCBs form a similar group of 209 related congeners that differ only in the number and pattern of chlorine atoms attached to the parent biphenyl molecule. 

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