Chlorinated biphenyl

The widespread use of biphenyl and methyl-substituted biphenyls as dye carriers (qv) in the textile industry has given rise to significant environmental concern because of the amount released to the environment in wastewater effluent. Although biphenyl and simple alkylbiphenyls are themselves biodegradable (48—50), the prospect of their conversion by chlorination to PCBs in the course of wastewater treatment has been a subject of environmental focus (51—53). Despite the fact that the lower chlorinated biphenyls are also fairly biodegradable (49,54,55) continued environmental concern has resulted in decreased use of biphenyl as a dye carrier (see Dyes, environmental chemistry). 

Chlorinated biphenyls, chlorinated naphthalenes, benzene hexachloride, [608-73-17, and chlorinated derivatives of cyclopentadiene are no longer in commercial use because of their toxicity. However, they still impact on the chemical industry because of residual environmental problems. This article discusses the toxicity and environmental impact of these materials. 

Chemical Designations - Synonyms Aroclor Chlorinated biphenyl Halogenated waxes PCB Polychloropolyphenyls Chemical Formula (C,2H x)Clx-... 

For transformer windings immersed in oil, hydrocarbon oil is the most widely used, whereas in areas where fire risk is a problem, then air-cooled transformers (AN) or synthetic silicon-based liquid cooling (SN) can be specified. Silicon-based liquids do not have any of the disadvantages identified with the chlorinated biphenyls. Air-cooled transformers can be provided with Class C insulation or be cast resin insulated. The relative costs per unit of each type are ... 

Generally, higher catalyst concentration leads to side reactions. An efficient approach to minimize the side reactions is to use the minimum amounts of Friedel-Crafts catalyst (e.g., FeCl3, 0.1-4 wt%). The reaction can be performed either in bulk or in solution using, for example, nitrobenzene, dimethyl sulfone, or chlorinated biphenyls as the reaction media. 

Several of the commercially available 16,000 chlorinated and brominated compounds have already been regulated or harmed, CFCs, DDT and chlorinated biphenyls are typical examples. Many others are being phased out according to the Montreal Protocol on Substances that Deplete the Ozone Layer. This includes chlorinated solvents, methyl bromide and halons (e.g. CF3Br). The milder ozone destroyers, hydrochlorofluorocarbons (HCFCs) will also, eventually, be phased out. 

Koeman, J.H. and van Genderen, H. (1970). Tissue levels in animals and effects caused by chlorinated hydrocarbon insecticides, chlorinated biphenyls, and mercury in the marine environment along the Netherlands coast. FAO Technical Conference on Marine Pollution. Rome, December 1970. 

Lntz RJ, Dedrick RL, Matthews FEB, Fling TE, Anderson MW. A preliminary pharmacokinetic model for several chlorinated biphenyls in the rat. Drug Metab Dispos 1977 5 386-396... 

Corke CT, NJ Bunce, A-L Beaumont, RL Merrick (1979) Diazonium cations as intermediates in the microbial transformations of chloroanilines to chlorinated biphenyls, azo compounds and triazenes. J Agric Eood Chem 27 644-646. 

Furukawa K, AM Chakrabarty (1982) Involvement of plasmids in total degradation of chlorinated biphenyls. Appl Environ Microbiol 44 619-626. 

Haddock JD, JR Horton, DT Gibson (1995) Dihydroxylation and dechlorination of chlorinated biphenyls by purified biphenyl 2,3-dioxygenase from Pseudomonas sp. strain LB400. J Bacteriol Yll 20-26. 

Arnett CM, JV Parales, JD Haddock (2000) Influence of chlorine snbstitnents on rates of oxidation of chlorinated biphenyls by the biphenyl dioxygenase of Burkholderia sp. strain LB400. Appl Environ Microbiol 66 2928-2933. 

A chlorinated biphenyl heat-transfer liquid was added to a burning batch of naph-thylsodium to help to extinguish it. An exothermic reaction, followed by an explosion occurred. Sodium is known to react violently with many halogenated materials. 

Bruggeman, W. A., van der Steen, J., Hutzinger, O. (1982) Reversed-phase thin-layer chromatography of polynuclear aromatic hydrocarbons and chlorinated biphenyls. Relationship with hydrophobicity as measured by aqueous solubility and octanol-water partition coefficient. J. Chromatogr. 238, 335-346. 

Sabljic, A., Lara, R., Ernst, W. (1989) Modelling association of highly chlorinated biphenyls with marine humic substances. Chemosphere 19, 1665-1676. 

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