Polychlorinated benzenes

In extension of the alkylation reactions to polychlorobenzenes, polychlorinated benzenes such as 1,2,4-trichlorobenzene and 1,2,., 4-tetrachlorobenzene were alkylated with (l,2-dichloroethyl)trichlorosilanes in the presence of aluminum chloride catalyst. Although the electron-withdrawing chlorine substituents on the ring deactivated the electrophilic substitution reaction, the alkylation... 

The pyrolysis of vinylidene chloride produced a range of chlorinated aromatic compounds including polychlorinated benzenes, styrenes, and naphthalenes (Yasahura and Morita 1988), and a series of chlorinated acids including chlorobenzoic acids has been identified in emissions from a municipal incinerator (Mowrer and Nordin 1987). 

Attention has been directed to the dechlorination of polychlorinated benzenes by strains that use them as an energy source by dehalorespiration. Investigations using Dahalococcoides sp. strain CBDBl have shown its ability to dechlorinate congeners with three or more chlorine substituents (Holscher et al. 2003). Although there are minor pathways, the major one for hexachlorobenzene was successive reductive dechlorination to pentachlorobenzene, 1,2,4,5-tetrachlorobenzene, 1,2,4-trichlorobenzene, and 1,4-dichlorobenzene (Jayachandran et al. 2003). The electron transport system has been examined by the use of specific inhibitors. lonophores had no effect on dechlorination, whereas the ATP-synthase inhibitor A,A -dicyclohexylcarbodiimide (DCCD) was strongly inhibitory (Jayachandran et al. 2004). 

Jones JP, EJ O Hare, L-L Wong (2001) Oxidation of polychlorinated benzenes by genetically engineered CYPlOl (cytochrome P450, jjj). Eur J Biochem 268 1460-1467. 

Hexachlorobenzene (HCB) was used as a pesticide to protect against fungus and in the manufacture of fireworks, ammunition, and synthetic rubber. This polychlorinated benzene now is foimd in coastal marine sediments. It also bioaccumulates in marine organisms. 

Figure 4.38 Phase transition temperatures of polychlorinated benzenes...

DDD Dichloro(chlorophenyl)-bis Ethane DDE Dichlorodiphenyldichloroethylene Dichlorobenzene, 1,2 Dichlorobenzene, 1,3 Dichlorobenzene, 1,4 Hexachlorobenzene Polychlorinated Benzenes Polychlorinated Biphenyls PCBs Aroclor Ring-Substituted Aromatics Tetrachlorobenzene Trichlorobenzene, 1,2,4 Saturated Alkyl Halides Bromodichloromethane Bromoform Tribromomethane Butyl Chloride Chlorobutane Carbon Tetrachloride Carbon Tetrafluoride Chloroform Trichloromethane Chloromethane Methyl Chloride Dibromochloromethane Dibromoethane, 1,2 Ethylene Dibromide Dibromomethane... 

Polychlorinated Benzenes under Ring-Substituted Aromatics Polychlorinated Biphenyls PCBs Aroclor under Ring-Substituted Aromatics... 

Chlorophenols may contain a variety of by-products and contaminants such as other chlorophenols, polychlorinated phenoxy-phenols and neutral compounds like polychlorinated benzenes and diphenyl ethers, PCDDs and PCDFs (39). Some of these contaminants may also occur in chlorophenol derivatives like phenoxy acids, other pesticides and hexachlorophene. The possible presence of PCDDs and PCDFs is of special significance because of their extraordinary toxicological properties. 

Hartonen et al. [286] have reported various extraction techniques for organochlorine insecticides in soils. Trapping efficiencies were reported for organochlorine insecticides, selected polychlorinated benzenes, polybromi-nated biphenyls, and polybrominated diphenyl ethers. 

Bioconcentration factors. Observed Bioconcentration Factors (based on lipid based concentrations in the organism, i.e., L water/L lipid) of non-metabolizable polychlorinated benzenes, biphenyls and naphthalenes ( ) and chlorodibenzo-p-dioxins (filled triangles) in Poecilia reticulata as a function of the chemical s octanol-water partition coefficient Kow. The figure illustrates the breakdown of the linear correlation between the BCF and Kow for chemicals with high Kow and the effect of metabolic transformation on the relationship between Kow and the BCF. 

Direct oxidation of the lesser chlorinated ethenes, ethanes, polychlorinated benzenes, and chlorobenzene has been reported. Wiedemeier et al. [25] summarize a number of studies that report direct aerobic oxidation of vinyl chloride (VC), 1,2-dichloroethane, the three dichlorobenzene isomers, 1,2,4-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene. Bradley [33] reports that DCE has served as a primary substrate for energy production with oxygen as the electron acceptor, though use of DCE as a sole carbon source has not been demonstrated. Rittmann and McCarty [29] also report that the two least chlorinated methanes (dichloromethane and chloromethane) as well as chloroethane can be directly oxidized under aerobic conditions. Direct oxidation of the chlorinated compounds is typically modeled using either first-order or Monod kinetics [29,31]. 

Initial runs using Cu-containing Y zeolites yielded remarkable conversion levels (T = 523-623 K residence time = 1-6 s concentration c = 23 or 37 mg/1, respectively). During these runs, however, we observed deactivation of the catalyst and deposition of crystalline by-products at the exit of the fixed bed reactor. These deposits were identified as congeners of polychlorinated benzenes by means of HRGC/MS. The phenomenon of transchlorination is also known in connection with the thermal decomposition of 1,2-dichlorobenzene [6,7], As we confirmed for catalytic experiments with unchlorinated aromatics carried out in our laboratory [8], no oxygenated products were released from the catalyst surface even in the case of chlorobenzene... 

K. Ballschmiter, R. Niemczyk, W. Shafer, W. Zoller, Isomer-specific identification of polychlorinated benzenes (PCBz) and biphenyls (PCB) in effluents of municipal waste incineration., Fresenius J. Anal. Chem., 328 (1997), 583-587. 

In a similar reaction, chlorinated thiophenols were added to a-acetamldoacryllc acid for the synthesis of mercapturlc acids of polychlorinated benzenes (196). This method produces a DL-mlxture of the N-acetyl-cystelne conjugate and It Is limited to the synthesis of mercapturlc acids and cysteine conjugates, the latter obtained after deacetylation. 

For a number of organic compounds, such as DDT, polychlorinated benzenes (PCBzs), biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and naphthalenes (PCNs), relationships between physical-chemical, physiological and bioaccumulation parameters have been established [18, 37, 41-43], which will be evaluated in the following sections. 

For soil, organic carbon and lipid normalized BSAFson in earthworms for a series of polychlorinated benzenes and biphenyls were between 0.4 and... 

Table 3. Interspecies variation in experimentally determined LBBs for narcotic chemicals (polychlorinated benzenes and polychlorinated biphenyls) ...

Ij, AICI3, etc.), its concentration, or the rate of feeding chlorine to the reactor. Higher temperature, however, gives higher yields of polychlorinated benzenes at any chlorination level. Lower reaction temperatures favor formation of para isomer. 

Single or multistage continuous chlorination gives higher yields of polychlorinated benzene at any chlorination level than batch chlorination. 

When all the benzene is to be chlorinated, the operation ceases when the density is 1.280 at 15 C. The time consumed is approximately 6 hr. At I.G. Farbenindustrie, Leverkusen, the temperature is controlled at 25-40 C and the density of the product at 1.06-1.1 to limit the quantity of polychlorinated benzene. 

Polychlorinated benzenes show overlapping primary bands and secondary bands around 220-250 and 300 nm respectively. It is well known that in conjugated biphenyls, styrenes and stilbenes, a medium-intense to intense band appears (the so-called K or conjugation band), located between the primary bands and the secondary band. In biphenyls, it is an intense band at 250-270 nm (Fig. 21) in styrenes, in the range 260-280 nm (Fig. 22) and in stilbenes, between 270 and 300 nm (Fig. 23). 

Wastes containing PAHs may be effectively destroyed by various incineration processes as mentioned briefly in the above section. Weber et al. (2001) have studied the mechanisms of formation of polychlorinated diben-zofurans (PCDF), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN) and polychlorinated benzenes (PCBz) from the degradation of PAHs in two types of incinerators, the stoker type- and the fluidized bed incinerators. Their studies have revealed the occurrence of a sequence of steps, such as the cleavage of C-C bond in the PAHs, chlorination at these cleaved positions, further chlorination or oxygen insertion at the ortho positions to the chlorine atoms in the intermediate chlorinated species. A perylene structure in soot is proposed as the basis for the observed PCDF pattern in the fluidized bed incinerators. Polychlorinated dibenzo-dioxins (PCDD) and the polychlorinated... 

Many halogenated hydrocarbons are known as environmental pollutants, for example, polychlorinated biphenyl (PCB), polychlorinated phenols (PCP), polychlorinated benzenes (PCBz), chloro-fluoro aliphatic carbons (CFC), and bromo-fiuoro aliphatic carbons (halone). As described in the previous section, solvated electrons that will attach to the solute whose electron affinity is positive, such as halogenated hydrocarbons, are effectively produced in polar solutions, such as an alcohol or ester. In this section, the dehalogenation mechanism in an alkaline 2-propanol solution (Mucka et al. 1997, Nakagawa 2003, Nakagawa and Shimokawa 2002, Sawai et al. 1974,1975, Shimokawa and Sawai 1977) is presented. The reaction mechanisms are summarized as follows in which R and R+ denote the radical and cation of 2-propanol, respectively, e soiv is the solvated electron, and M-X is the halogenated carbons (Reaction Mechanism 14.4). 

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