Ethenes, chlorinated

S(II) or pyrite amended Chlorinated ethenes, chlorinated phenols [94,252-254]... 

As with the ethenes, chlorinated ethanes will also undergo halorespiration. Dechlorination of 1,1,1 -TCA has been described by Vogel and McCarty and Cox et al. but understanding this pathway is complicated by the rapid hydrolysis reactions (e.g., half-life is 0.5-2.5 yrs) that can affect TCA. " Finally, halorespiration has been observed with highly chlorinated benzenes such as hexachlorobenzene, pentachlorobenzene, tetrachlorobenzene, and trichlorobenzene. " As discussed by Suflita and Townsend, halorespiration of aromatic compounds has been observed in a variety of anaerobic habitats, including aquifer materials, marine and freshwater sediments, sewage sludges, and soil samples. However, isolation of specific microbes capable of these reactions has been difficult. 

CH2C1 CH2C1. Colourless liquid with an odour like that of chloroform b.p. 84 C. It is an excellent solvent for fats and waxes. Was first known as oil of Dutch chemists . Manufactured by the vapour- or liquid-phase reaction of ethene and chlorine in the presence of a catalyst. It reacts with anhydrous ethano-ales to give ethylene glycol diethanoate and with ammonia to give elhylenediamine, these reactions being employed for the manufacture of these chemicals. It burns only with difficulty and is not decomposed by boiling water. 

Another common reaction is the chlorination of alkenes to give 1,2-dihaloalka-nes. Patell et al. reported that the addition of chlorine to ethene in acidic chloroalu-minate(III) ionic liquids gave 1,2-dichloroethane [68]. Under these conditions, the imidazole ring of imidazolium ionic liquid is chlorinated. Initially, the chlorination occurs at the 4- and 5-positions of the imidazole ring, and is followed by much slower chlorination at the 2-position. This does not affect the outcome of the alkene chlorination reaction and it was found that the chlorinated imidazolium ionic liquids are excellent catalysts for the reaction (Scheme 5.1-39). 

One of the products of the reaction of sulfur with chlorine is disulfur dichloride, S2C12, a yellow liquid with a nauseating smell it is used for the vulcanization of rubber. When disulfur dichloride reacts with more chlorine in the presence of iron(III) chloride as a catalyst, the foul-smelling red liquid sulfur dichloride, SC12, is produced. Sulfur dichloride reacts with ethene to give mustard gas (16), which has been used in chemical warfare. Mustard gas causes blisters, discharges from the nose, and vomiting it also destroys the cornea of the eye. All in all, it is easy to see why ancient civilizations associated sulfur with the underworld. 

Compare the reaction enthalpies for the halogenation of ethene by chlorine, bromine, and iodine. What trend, if any, exists in these numbers Use bond enthalpies to estimate the enthalpies of reaction. 

Classify each of the following reactions as addition or substitution and write its chemical equation (a) chlorine reacts with methane when exposed to light (b) bromine reacts with ethene in the absence of light. 

Fogel MM, Taddeo AR, Fogel S. 1986. Biodegradation of chlorinated ethenes by a methane-utilizing mixed culture. Appl Environ Microbiol 51 720-724. 

Jeffers PM, Ward LM, Woytowitch LM, et al. 1989. Homogenous hydrolysis rate constants for selected chlorinated methanes, ethanes, ethenes and propanes. Environmental Science and Technology 23 965-969. 

There has been considerable interest in the abiotic dechlorination of chlorinated ethenes at contaminated sites. Reductive dehalogenation has therefore been examined using a range of reductants, many of them involving reduced complexes of porphyrins or corrins. 

Using a polymer electrolyte membrane cell in which flowed through the anode chamber. The major intermediate chlorinated products from tetrachloroethene or tet-rachloromethane were trichloroethene or trichloromethane, and these were finally reduced to a mixture of ethane and ethene, or methane (Liu et al. 2001). 

Attention is drawn to the dechlorination by anaerobic bacteria of both chlorinated ethenes and chlorophenolic compounds that serve as electron acceptors with electron donors including formate, pyruvate, and acetate. This is termed dehalorespiration and is important in the degradation of a range of halogenated compounds under anaerobic conditions, and is discussed further in Chapter 3, Part 2 and Chapter 7, Part 3. 

Maym6-Gatell X, T Anguish, SH Zinder (1999) Reductive dechlorination of chlorinated ethenes and 1,2-dichlooroethane by Dehalococcoides ethenogenes" 195. Appl Environ Microbiol 65 3108-3113. 

Numata M, N Nakamura, H Koshikawa, Y Terashima (2002) Chlorine isotope fractionation during reductive dechloirination of chlorinated ethenes by anaerobic bacteria. Environ Sci Technol 36 4389-4394. 

Particularly the chlorinated compounds have enjoyed range of applications vinyl chloride (chloro-ethene) as monomer for the production of PVC, tetra- and trichloroethenes as solvents for degreasing, and the insecticides l,l,l-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and isomers of hexachlorocyclohexane (HCH) (benzene hexachloride). The biodegradation of fluorinated aliphatic compounds is generally different from the outlines that have emerged from investigations on their chlorinated, brominated, and even iodinated analogues. They are therefore treated separately in Part 4 of this chapter. 

Three anaerobic dechlorinating consortia were used to examine fractionation during dechlorination of tetrachloroethene and TCE to cii-dichloroethene (Numata et al. 2002). Fractionation factors (a) for the first reaction ranged from 0.987 to 0.991 for the three consortia, and for the second reaction were 0.9944 for all consortia. Some important limitations were pointed out (a) the chlorinated ethenes were not separated so that the isotopic... 

Slater GF, BS Lollar, BE Sleep, EA Edwards (2001) Variability in carbon isotope fractionation during biodegradation of chlorinated ethenes implications for field applications. Environ Sci Technol 35 901-907. 

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