2,4,5,2 ,4’,5 Hexachloro-biphenyl

Evans, M.S. and P.F. Landrum. 1989. Toxicokinetics of DDE, benzo(a)pyrene, and 2,4,5,2, 4, 5 -hexachloro-biphenyl in Pontoporeia hoyi and Mysis relicta. Jour. Great Lakes Res. 15 589-600. 

Along with degree of chlorination another determinant of PCB metabolism in fish is species. Green sunfish and goldfish rapidly metabolize 2,2, 5-trichlorobiphenyl whereas bullheads and rainbow trout metabolize it slowly (26,29). There is little evidence for PCB metabolism in brook trout fed 4-chloro-, 4,4 -dichloro-, 2,2, 5,5 -tetrachloro- or 2,2, 4,4, 5,5 -hexachloro-biphenyl (31) and this was confirmed in rainbow trout by less than 1% of 2,2, 5,5 -tetrachlorobiphenyl accumulated being recovered as polar metabolites (25). 

Polybrominated Biphenyls. The photolytic degradation of PBBs in solution has been the subject of several studies. Available data in the literature indicate that brominated biphenyls photodegrade by reduction in solvents capable of proton transfer with the formation of lower brominated biphenyls. For example, the irradiation of FireMaster BP-6 and 2,2, 4,4, 5,5 -hexabromobiphenyl in methanol at wavelengths >286 nm produced mainly penta- and tetrabromobiphenyl (Ruzo and Zabik 1975). FireMaster BP-6 photolyzed7 times faster than its chlorinated counterpart, 2,2, 4,4, 5,5 -hexachloro-biphenyl (Ruzo and Zabik 1975). Although an earlier study tentatively identified dimethoxy tetrabromobiphenyl as a photolysis product of FireMaster BP-6 (Ruzo and Zabik 1975), later work did not detect this compound (Ruzo et al. 1976). Earlier studies indicated that the debromination usually occurs with the stepwise preferential loss of bromine from the ortho and para positions of the biphenyl ring (i.e., 2, 2, 6, and 6 positions) (De Kok et al. 1977 Ruzo and Zabik 1975 Ruzo et al. 1976 Trotter 1977). Thus, the photolysis of 2,2, 4,4, 5,5 -hexachlorobiphenyl, the major component of FireMaster BP-6, would be expected to produce 23, 4,4, 5-pentabromobiphenyl and subsequently... 

PROP Average content, 55% pentachlorobiphenyl, 26.5% tetrachlorobiphenyl, 12.8% hexachloro biphenyl, and 5% trichlorobiphenyl QNCIAM 51,1637,73). 

Naphthalene Naphthalene Naphthalene Naphthalene Phenanthrene Phenanthrene Naphthol Naphthalene 4-chlorobiphenyl 4-chlorobiphenyl 4-chlorobiphenyl 2, 4, 6-trichloro-biphenyl 2, 2, 4, 4, 6, 6 -hexachloro-biphenyl Anthracene Anthracene Anthracene Anthracene Anthracene Atrazine Atrazine Naphthalene Naphthalene Naphthalene Naphthalene Naphthalene... 

Wyss PA, Muhlebach S, Bickel MH. 1986. Long-term pharmacokinetics of 2,2, 4,4, 5,5 -hexachloro-biphenyl (6-CB) in rats with constant adipose tissue mass. Drug Metab Dispos 14 361-365. 

In this context, Di Toro et al. [1] made batch-experiments on the equilibrium of sorption of hexachloro-biphenyl on montmorillonite and constructed a sorption model. They additionally considered the partial reversibility of this sorption process. A. M. Rodrigo and... 

Ingenious experiments to which reference has already been made have used addition of specific PCB congeners that are more readily dechlorinated to prime dechlorination at specific positions (Bedard and Quensen 1995). They have been extended to the use of dibrominated biphenyls in the presence of malate to stimulate dechlorination of the hexachloro- to nanochlorobiphenyls (Bedard and Quensen 1995). Results from these experiments provide valuable evidence of important differences between anaerobic dechlorination and anaerobic debromination, and the greater facility of the latter. 

Other componnds have also been examined as primers for the dechlorination of hexachloro to nonachloro PCB congeners (DeWeerd and Bedard 1999) a nnmber of snbstituted brominated monocyclic aromatic componnds were examined, and 4-bromobenzoate was effective—though less so than 2,6-dibromobiphenyl. In contrast, the chlorobenzoates that are metabolites of aerobic degradation were ineffective. The positive effect of brominated biphenyls in priming the anaerobic dechlorination of CBs has also been encountered in the dechlorination of octachlorodibenzo[l,4] dioxin to the 2,3,7,8 congener indnced by 2-bromodibenzo[l,4]dioxin in the presence of (Albrecht... 

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