3,4,2 -Trichloro-biphenyl

In contrast, Williams and May [151] investigated the low-temperature (e.g., 4 °C) microbial aerobic PCB degradation of PCB-contaminated upper Hudson River sediments. They reported the depletion of specific di- and trichloro-biphenyls in the surface layer of PCB-contaminated sediments. The loss of specific PCB congeners from the sediment was indicative of microbial aerobic PCB degradation and demonstrated that this degradation can occur in sediment samples at low temperatures. 

DeWeerd and Bedard [253] investigated novel approaches for enhancing microbial PCB dechlorination in aquatic sediments of the Housatonic River. They reported that PCB dechlorinating microorganisms were activated (i.e., primed) to dechlorinate the PCBs that have persisted for years in these sediments. Several PCB congeners, especially 2,3,4,5,6-pentachlorobiphenyl (23456-CB), 2,3,4,6-tetrachlorobiphenyl (2346-CB), and 2,3,6-trichloro-biphenyl (236-CB), were shown to prime and sustain mefa-dechlorination of Aroclor 1260 in the river sediment, whereas the PCB congener 245-CB primed para-dechlorination of PCBs in the same sediments. 

Assuming that no significant in-situ degradation of PCBs occurs (k htm = photo = Kio = 0 ) three elimination pathways remain which, if described in terms of first-order reaction rates, can be directly compared with respect to their relative importance for the elimination of each PCB congener from the water column. As shown by the removal rates listed in Table 23.4, for both compounds the flux to the atmosphere is by far the most important process. Because of its larger Kd value, removal of the heptachlorobiphenyl to the sediments is predicted to be also of some importance. By the way, from this simple model we would expect to find the heptachlorobiphenyl relatively enriched in the sediments compared to the trichloro-biphenyl. We shall see later whether this is true. 

The atmospheric concentration of 2,4,4/-trichloro-biphenyl (a PCB) averages 1.9pg/m3 throughout the Earth s atmosphere, and the second-order rate constant for the reaction of this PCB with OH is 1.1 x 10 12cm3/s. [P.N. Anderson and R.A. Hites, Environmental Science and Technology 30, 1756-1763 (1996)]. What is the residence time of this PCB in the troposphere due to this reaction You may assume that the atmospheric concentration of OH is 9.4 x 105 cm 3 and that the molecular weight of this PCB is 256. 

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... 

It can be seen from the structure that a large number of chlorinated compounds are possible. The 209 possible compounds are called congeners. PCBs can also be categorized by degree of chlorination. The term homolog is used to refer to all PCBs with the same number of chlorines (e.g., trichloro-biphenyls). Homologs with different substitution patterns are referred to as isomers. For example, the dichlorophenyl homolog contains 12 isomers. 

A number of commercial PCB formulations have been tested for their degradability by microbes in aerobic activated sludge in a semicontinuous operation. Similar to animal metabolic results, mono-, di-, and trichloro-biphenyls are significantly biodegraded and volatilized, whereas PCBs with... 

Mizutani and coworkers57a confirmed the presence of polychloro(methylsulfonyl)biphenyls (159-170) as sulfur-containing metabolites of chlorobiphenyls (Cl-BP) in the feces of mice based on both GLC-mass spectrometry and chemical derivatization. In some cases comparison with authentic samples (161 and 162) was also made. When preparing 161 and 162,2,5-dichloro-3-(methylsulfonyl)aniline, 2,5-dichloro-l-iodo-3-(methylsulfonyl)benzene and 2,2, 5,5 -tetrachloro-3,3 -bis(methyl-sulfonyl)biphenyl were also obtained and their four peak El mass spectra reported572. Similar data were given for the corresponding 4-substituted intermediates, which were involved in the preparation of 162. Also 2,4, 5-trichloro-2 -(methylsulfonyl)-biphenyl was prepared and its four peak mass spectra given. Metabolites 163 and 164 were also identified by comparison with the authentic standards. 

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

Trichlorodihydroxybiphenyl, see TCDD 2,2,3 -Trichloro-2,4 -di-7V,7V-dimethylurea biphenyl, see Diuron... 

Common Name 2,2, 3-Trichlorobiphenyl Synonym PCB-16, 2,2, 3-trichloro-1,1 -biphenyl Chemical Name 2,2, 3-trichlorobiphenyl CAS Registry No 38444-78-9 Molecular Formula Ci2H7C13 Molecular Weight 257.543 Melting Point (°C) ... 

Note Binary combinations at the 1188 sites surveyed. MeCl = methylene chloride, PCBs = polychlorinated biphenyls, Perc = perchloroethylene (tetrachloroethylene), 1,1,1-TCA = 1,1,1-trichloro-ethane, TCE = trichloroethylene, Trans-1,2-DCE = trans-l,2-dichloroethylene, 1,1-DCA = 1,1-dichloroethane, 1,1-DCE = 1,1-dichloroethene. 

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