Polybrominated products

Unlike the violent bromination of pyrrole or indole, which leads to polybrominated products, the bromination of pyrrolopyridines proceeds readily to a monobrominated product. Table 39 lists some of the pyrrolopyridine derivatives that have been brominated. Common solvents for these bromination reactions are chloroform, dioxane, or acetic acid. 

The direct bromination of aliphatic ketones occurs readily, often giving isomeric mixtures. Thus, methyl ethyl ketone and an equimolar quantity of bromine yield the a-btomomethyl (17%) and the a-bromoethyl (50%) isomers polybrominated products are also formed. On the other hand, only the tertiary hydrogen in methyl isopropyl ketone is substituted upon monobromination. By varying the conditions for the bromination of acetone, mono- or poly-substitution products may be formed e.g., bromo-acetone (44%), a,a -dibromoacetone (60%), and a,a,a -tribromoacetone (60%). ... 

Incineration of a collection of polymers with 10 different kinds of brominated flame retardants has been studied under standardized laboratory conditions using varying parameters including temperature and air flow. Polybrominated diphenyl ethers like the deca-, octa-, and pentabromo compounds yield a mixture of brominated dibenzofurans while burning in polymeric matrices. Besides cyclization, debromination/hydrogenation is observed. Influence of matrix effects and burning conditions on product pattern has been studied the relevant mechanisms have been proposed and the toxicological relevance is discussed. 

The principal source of pollution by polybrominated biphenyls (PBBs) has been the commercial mixture Firemaster, which was produced in the United States between 1970 and 1974. Production was discontinued in 1974 following a severe pollution incident in Michigan, when Firemaster was accidentally mixed with cattle feed on a farm. In due course, PBBs entered the human food chain via contaminated animal products. Substantial residues were found in humans from the area, and were snbse-quently found to be highly persistent. 

The structural range of industrially important representatives of these groups is enormous, and includes chlorobenzenes (solvents), polychlorinated biphenyls (PCBs) (hydraulic and insulating fluids), and polybrominated biphenyls and diphenyl ethers (flame retardants). There is widespread concern over both the persistence and the potential toxicity of all these compounds, and sites that have become contaminated during their production represent a threat both to the environment and to human health. Pathways for the aerobic bacterial degradation of chlorobenzenes and chlorobiphe-nyls, and their brominated analogs have been discussed in Chapter 9, Part 1. 

Buser H-R (1986) Polybrominated dibenofurans and dibenzo-p-dioxins thermal reaction products of polybro-minated diphenyl ether flame retardants. Environ Sci Technol 20 404-408. 

For this purpose, the WEEE Directive has been complemented with an additional directive that limits the use of certain pollutants in these products. The EC Directive 2002/95/EC on the Restriction of the use of certain Hazardous Substances in electrical and electronic equipment (RoHS Directive) ([7], recast 2011 [9]) restricts the use of the six harmful substances/substance families lead, mercury, hexavalent chromium, polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE) to 0.1% and cadmium to 0.01% w/w per homogenous material in equipment and components, but with several exemptions for a wide range of applications (Annex III and IV). 

BFRs are one of the last classes of halogenated compounds that are still being produced worldwide and used in high quantities in many applications. In order to meet fire safety regulations, flame retardants (FRs) are applied to combustible materials such as polymers, plastics, wood, paper, and textiles. Approximately 25% of all FRs contain bromine as the active ingredient. More than 80 different aliphatic, cyclo-aliphatic, aromatic, and polymeric compounds are used as BFRs. BFRs, such as polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), have been used in different consumer products in large quantities, and consequently they were detected in the environment, biota, and even in human samples [26, 27]. 

Sites near industrial areas in the Ebro have been found to have the highest concentration of priority contaminants [15, 47—49], while dispersion of agricultural products by drift, runoff and drainage has resulted in residues being found in ground-waters, rivers, coastal waters and lakes far from point sources [50]. Priority contaminants in aquatic environments include persistent organic pollutants (POPs) such as dichlorodiphenylethylenes (DDT) and polybrominated diphenyl ethers (PBDEs). 

Note Unless the word "monobrominated" had been used in the problem, a whole host of products would have been possible i.e. polybrominated ethanes, polymers, and so on. 

Decabromodiphenyl ether (BDE-209) is a major industrial product from the polybrominated diphenyl ethers used as flame retardants derivatives of this product have been detected in the environment. After exposure to the land surface, these contaminants adsorb on soil materials and may reach the atmosphere as particulate matter these particulates are subsequently subject to photolytic reactions. In this context, Ahn et al. (2006) studied photolysis of BDE-209 adsorbed on clay minerals, metal oxides, and sediments, under sunhght and UV dark irradiation. Dark and light control treatments during UV and sunlight irradiation showed no disappearance of BDE-209 during the experiments. Data on half-lives and rate constants of BDE-209 adsorbed on subsurface minerals and sediments, as determined by Ahn et al. (2006) and extracted from the literature, are shown in Table 16.6. 

The POCs include, but are certainly not limited to the polychlorinated biphenyls (PCBs) and the organochlorine pesticides, including those in current use, restricted use and historic use brominated flame retardants including polybrominated diphenyl ethers PAHs and the sometimes more toxic transformation products of these chemicals. Table 1 summarizes information on some of the POCs more commonly detected in alpine environments. 

Uses. Polybrominated biphenyls (PBBs) are compounds that were formerly used as flame retardants in electrical products and in business machines and motor housings. There are 209 possible bromobiphenyl congeners, although only a small number have been synthesized and used. All of the commercial products contained a mixmre of several individual PBBs. Commercial production ceased in 1977. 

Polybrominated hydrocarbons Used in the manufacture of plastic products. Bioaccumulate and are highly persistent in the environment... 

The emerging pollutants also include perfluorooctanoic acid (PFOA) and perfluorooctanesul-fonate (PFOS), used in the production of water-resistant coatings and polybrominated diphenylether (PBVDF) that find application in furniture, textiles, plastics, and paint industries. Due to their large industrial use, these chemicals are present profusely in the environment and also in the blood of people working in the fields [21]. 

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