Carbon tetrachloride reductive dehalogenation

Curtis GP, M Reinhard (1994) Reductive dehalogenation of hexachloroethane, carbon tetrachloride, and bromoform by anthrahydroquinone disulfonate and humic acids. Environ Sci Technol 28 2393-2401. 

FIGURE 5.15 Reductive dehalogenation of carbon tetrachloride results in a carbon-centered free radical that reacts rapidly with oxygen to form the toxic peroxy radical. 

Currtis GP, Reinhard M. 1992. Reductive dehalogenation of hexachlorethane, carbon tetrachloride and bromoform by anthrahydroquinone disulftonate and humic acid. AbstrPap Am Chem Soc 203 91. 

Nakata, Y, Iwai, M., Kimura. S. Shimazu. T. (1996) Prolonged decrease in hepatic connexin 32 in chronic liver injury induced by carbon tetrachloride in rats. J. Hepatol., 25, 529-537 Nastainczyk, W., Ahr, H. Ulrich. V. (1991) The mechanism of the reductive dehalogenation of... 

The dehalogenation process has been approved by the EPA s Office of Toxic Substances for PCB treatment and has been experimentally implemented for the cleanup of PCB-contaminated soil at the following three Superfund sites Wide Beach in Erie County, New York (1985) Re-Solve in Massachusetts (1987) and Sol Lynn in Texas (1988). The glycolate process has been used to successfully treat contaminant concentrations of PCBs from less than 2 ppm to reportedly as high as 45,000 ppm. Using this technology, Helland et al. (1995) investigated reductive dechlorination of carbon tetrachloride with elemental iron and found that the rate of dechlorination to chloroform and methylene chloride was a fast first-order process. 

The reaction proceeds until each chlorine ion is removed. For example, carbon tetrachloride would be reduced to chloroform, then to methylene chloride, and finally to methane (the reduction of methylene chloride takes several months, however). No degradation products other than the parent compounds were found therefore, degradation is simple, reductive dechlorination, with the zero-valent iron serving as an electron donor. The reaction was pseudo first-order and the reaction constant, k, decreased with each additional dehalogenation step (Gillham and O Hannesin, 1994). 

Warren, K.D., Arnold, R.G., Bishop, T.L., Lindholm, L.C., and Betterton, E.A., Kinetics and mechanism of reductive dehalogenation of carbon tetrachloride using zero-valence metals, /. Hazardous Mater., 41, 217-227, 1995. 

Rodriguez, J.C., and M. Rivera. 1997. Reductive dehalogenation of carbon tetrachloride by sodium dithionite. Chem. Lett. 1133-1134. 

A tri-dimensional electrode reactor geometry was studied by He et al. (2004a, b) to overcome the problem of low conductivity media (>1 S m-1). The reduction of model carbon tetrachloride was performed on a porous copper foam with good conversion rates and almost total dehalogenation of the substrate. 

FIGURE 32.4 The CYP-catalyzed reductive dehalogenation of carbon tetrachloride (2) leading to the reactive trichloromethyl radical (3). The latter reacts, among others, with molecular oxygen to form a peroxyl radical (4). 

Figure 23.2.2. Anaerobic degradation of carbon tetrachloride. An example of anaerobic dehalogenation, using carbon tetrachloride as the model compound. In many cases, these reactions occur under cometabolic conditions meaning that an alternative growth substrate must be present to serve as an electron donor to drive the reduction reactions whereby carbon tetrachloride is used as the electron acceptor. Three known pathways for microbial degradation of carbon tetrachloride have been identified [U.E. Krone, R.K. Thauer, H.P. Hogenkamp, and K. Steinbach, Biochemistry, 3d 0), 2713 (1991) C.H. Lee, T.A. Lewis, A. Paszczynski, andR.L. Crawford Biochem Biophys Res Commun, 261(3), 562 (1999)]. These pathways are not enzymatically driven but rely on corrinoid and corrinoid-like molecules to catalyze these reactions.

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