Organochlorine compounds, oxidants

X-ray absorption spectroscopy has revealed the formation of organochlorine compounds from chloride and chloroperoxidase in weathering plant material (172-174). Moreover, this technique has uncovered the bromide-to-organobromine conversion in environmental samples (174). In addition to chloroperoxidase mediated chlorination, the abiotic chlorination in soils and sediments involving the alkylation of halides during Fe(III) oxidation of natural organic phenols in soils and sediments has been discovered (175-177). 

Beltran, F.J., Gonzalez, M., Acedo, B., and Jaramillo, J., Contribution of free radical oxidation to eliminate volatile organochlorine compound in water by ultraviolet radiation and hydrogen peroxide, Chemosphere, 32(10), 1949-1961, 1996c. 

Pedit et al. [226] used a kinetic model for the scale-up of ozone/hydrogen peroxide oxidation of some volatile organochlorine compounds such as trichloroethylene and tetrachloroethylene. The kinetic model was applied to simulate the ozone/hydrogen peroxide treatment of these pollutants in a full-scale demonstration plant of the Los Angeles Department of Water and Power. The authors confirmed from the model that the reaction rate of the pollutant with ozone was several orders of magnitude lower than that with the hydroxyl radical. When considering that the natural organic matter acts as a promoter of hydroxyl radicals, the ozone utilization prediction was 81.2%, very close to the actual 88.4% experimentally observed. 

Many groundwaters are contaminated with the cleaning solvents trichloroethylene (TCE) and perchloroethylene (PCE). They are two of the most common organochlorine compounds found in Superfund sites. Radiation-induced decomposition of TCE in aqueous solutions has been the subject of several recent studies [15-20]. In most of the referenced studies, the complete destruction of TCE was observed. Dechlorination by a combination of oxidative and reductive radiolysis was stoichiometric. Gehringer et al. [15] and Proksch et al. [18] have characterized the kinetics and mechanism of OH radical attack on TCE and PCE in y-ray-irradiated aqueous solution. Trichloroethylene was readily decomposed in exponential fashion, with a reported G value of 0.54 pmol J-1. A 10 ppm (76 pM) solution was decontaminated with an absorbed dose of less than 600 Gy. For each OH captured, one C02 molecule, one formic acid molecule and three Cl- ions were generated. These products were created by a series of reactions initiated by OH addition to the unsaturated TCE carbon, which is shown in Eq. (45) ... 

Organochlorine compounds with chlorine bonded to nitrogen give different oxidation products, depending on the nature of the organic molecule. 

The formation of phosgene by the aerial oxidation of chlorinated organic compounds is of considerable industrial interest and has been considered, in its proper context, in some detail in Section 3.3, whilst the in vivo and in vitro formation of phosgene from organochlorine compounds has been discussed in Section 2.5.4. Only those reactions which might constitute a synthetic procedure will be considered here. 

S and N are cycled by life and by atmospheric photochemistry through many oxidation states. Natural Si and P compounds are involatile and less mobile in the environment. Environmental problems include acid rain, and pollution by soluble phosphates and organochlorine compounds. 

Chlorine is a side product. Subsequent chlorine bleaching of the brown pulp gives a product that can be used for the manufacture of writing and printing paper. Unfortunately, organic compounds in the pulp are both oxidized and chlorinated, yielding small quantities of organochlorine compounds, in-... 

The most conspicuous organic contaminants of seawater are organochlorine compounds (Broman et al., 1991), fossil hydrocarbons and their oxidation products Ehrhardt and Bums, 1993), linear alkylbenzenes, alkylphenols (Marcomini et al, 1990 Blackburn and Waldock, 1995), and phthalate esters Waldock, 1983). Concentration procedures for these lipophilic substances are described here. However, the analyst should be aware of the fact that contaminants are not the only lipophilic chemicals likely to be present in seawater. A large number of recently biosynthesised, as well as man made chemicals not listed above, will also be concentrated by these methods. 

Strength as an oxidizing agent. There is, however, pressure to reduce the use of chlorine gas and organochlorine compounds, because they can lead to the environmental release of chlorinated hydrocarbons, which may cause cancer and other kinds of adverse health effects. The danger compounds include the notorious dioxin (Structure 6.2), which is a degradation product of organochlorine pesticides and other similar compounds. 

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