Polybromination

Bromine can replace sulfonic acid groups on aromatic rings that also contain activating groups. PhenoHc sulfonic acids, for example, are polybrominated (24). 

Alkylphenols, ammonia, asbestos, chlorinated paraffins, 4-chloroaniline, cyanide, detergents, di- -butyl phthalate, polyaromatic hydrocarbons (PAHs e.g. anthracene, benzopyrene, methylcholanthrene, /i-naphthoflavone), nitrate, nitrite, petroleum oil, phenol, pentachlorophenol, 4-nitrophenol, dinitro-o-cresol, polychlorinated biphenyls (PCBs especially coplanar), polychlorinated dioxins, polybrominated naphthalenes, /i-sitosterol, sulfide, thiourea, urea, acid water, coal dust... 

Dimethyl-2,l,3-benzoselenadiazole was brominated on the methyl groups by NBS (87CB1593), but halogenation of the unsubstituted compound occurred, as with the sulfur analogue, at the 4(7)-position initially. Polybromination can occur (64JGU3063). 

A variety of complexes exists in solid or liquid state at ambient temperature, in the range required for battery operation. Liquid polybromine phases are preferred since they enable storage of the active material externally to the electrochemical cell stack in a tank, hence enhancing the... 

As shown by several investigations [91], the bromine-rich polybromide phase by itself is hardly flammable and fireextinguishing properties have been reported occasionally. The formation of polybrominated dibenzo-dioxins (PBrDD) and furans (PBrDF) due to the plastic-containing housing of a zinc-flow battery cannot be totally neglected in the case of a fire, but their concentrations are far away from the tetrachloro dibenzodioxine (TCDD) toxic equivalents even in a worst-case scenario. 

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. 

Scheme 3. Mechanism of Copper Catalyzed Formation of PBDD from Polybrominated Diphenyl Ethers.

M. Freiberg, D.L. McAllister, C.J. Mazac, P. Ranken Analysis of Trace Levels of Polybrominated Dibenzo-p-dioxins and Dibenzofurans in Brominated Flame Retardants Presented on June 30, 1993 at Orgabrom 93 in Jerusalem. 

Except for polybrominated biphenyls (PBB), a limited number of studies regarding the toxicity of aromatic brominated compounds has been performed. Some experiments suggest a moderate acute toxicity of these compounds (ref. 1). 

Among aromatic bromine derivates, only polybrominated biphenyl is known to have a porphyrogenic effect (ref. 24). From scarce data about the toxicity of 4 and 5 porphyrogenic activity in the case of repeated administration could be expected (refs. 25,26). No data are available concerning the remaining compounds. 

The polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs) are indnstrial chemicals that do not occur naturally in the environment. The properties, uses, and toxicology of the PCBs are described in detail in Safe (1984), Robertson and Hansen (2001), and Environmental Health Criteria 140. PBBs are described in Safe (1984) and Environmental Health Criteria 152. 

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. 

Costa, L.G. and Giordano, G. (2007). Developmental neurotoxicity of polybrominated diphenyl ether (PBDE) flame retardants. Neurotoxicology 28, 1047-1067. 

Environmental Health Criteria 152 (1994). Polybrominated biphenyh. Geneva WHO. 

Gustafsson, K., Bjork, M., and Burreau, S. et al. (1999). Bioaccumulation kinetics of bromi-nated flame retardants (polybrominated diphenyl ethers) in blue mussels (Mytilus edu-lis). Environmental Toxicology and Chemistry 18, 1218-1224. 

Hale, R.C., La Guardia, M.J., and Harvey, E.P. et al. (2001). Polybrominated diphenyl ether flame retardants in Virginia freshwater fishes (USA). Environmental Science and Technology 35, 4585 591. 

Luross, J.M., Alaee, M., and Sergeant, D.B. et al. (2002). Spatial distribution of polybromi-nated diphenyl ethers and polybrominated biphenyls in lake trout from the Laurentian Great Lakes. Chemosphere 46, 665-672. 

Pijnenburg, A., Everts, J., and de Boer, J. et al. (1995). Polybrominated biphenyl and diphe-nylether flame retardants analysis, toxicity, and environmental occurrence. Reviews in Environmental Contamination and Toxicology. 141, 1-26. 

Safe, S. (1984). Polychlorinated biphenyls and polybrominated biphenyls biochemistry, toxicology and mode of action CRC Critical Reviews in Toxicology 13, 319-395. 

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