Polychlorinated dibenzodioxins structures

Dioxins are a particular group of chlorinated organic molecules which have been associated with pulp and paper production and are a concern because of their extreme toxicity. There are two groups of molecular types which fall into the general category referred to as dioxins. These are the polychlorinated dibenzodioxins (PCDDs) and the polychlorinated dibenzofurans (PCDFs). The structures of these molecules are shown in Figure 10.4. 

Figure 10.4 The structures of polychlorinated dibenzodioxins and polychlorinated dibenzofurans...

Beger, R.D., Buzatu, D.A. and Wilkes, J.G. (2002) Combining NMR spectral and structural data to form models of polychlorinated dibenzodioxins, dibenzofurans, and biphenyls binding to the AhR. Journal of Computer-Aided Molecular Design, 16, 727-740. 

De Voogt, P, Muir, D.C.G., Webster, G.R.B., Govers, H. (1990) Quantitative structure-activity relationships for the bioconcentration in fish of seven polychlorinated dibenzodioxins. Chemosphere 21, 1385-1396. 

The polychlorinated dibenzodioxins (PCDDs) and dibenzofurans are two groups of compounds that exhibit similar chemical and physical properties, the chemical structures are given below ... 

Polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are chemically classified as halogenated aromatic hydrocarbons. The chlorinated and brominated dibenzodioxins and dibenzofurans are tricyclic aromatic compounds with similar physical and chemical properties, and both classes are similar structurally. Certain of the PCBs (the so-called coplanar or mono-ortho coplanar congeners) are also structurally and conformationally similar. The most widely studied of these compounds is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This compound, often called simply dioxin, represents the reference compound for this class of compounds. The structure of TCDD and several related compounds is shown in Figure 4.1. 

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>. 

This chapter is divided into seven main sections. The first of these sections is focused on technological contaminants, namely heterocyclic amines, acrylamide, furan, chloropropanok and their fatty acid esters, polycycKc aromatic hydrocarbons, monocyclic aromatic hydrocarbons, nitroso compounds, and ethyl carbamate. Other sections deal with microbial toxins (mycotoxins and bacterial toxins), persistent organohalogen contaminants (such as polychlorinated biphenyls, dibenzodioxins and dibenzofurans), chlorinated ahphatic hydrocarbons, pesticides (persistent chlorinated hydrocarbons and modem pesticides), veterinary medicines and contaminants from packaging materials. Presented for each of these contaminants are structures, properties, occurrence and the main sources of dietary intake, mechanisms of formation, possibilities of food contamination, prevention and mitigation and health and toxicological evaluations. 

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