Dechlorination vitamin

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

Lesage, S., Brown, S., and Millar, K., 1996, Vitamin B12 — Catalized Dechlorination of Perchloroethylene Present as Residual DNAPL Ground Water Monitoring Remediation, Vol. 16, No. 4, pp. 76-85. 

Schanke and Wackett [379] reported TeCA degradation by transition-metal coenzymes. cDCE (53%), tDCE (29%), VC (14%), ethylene (1%), and traces of 1,1,2-TCA were the products from this abiotic transformation with vitamin B12 and titanium(III) citrate. Both dechlorination and dichloroelimination had occurred the major route of degradation was reductive dihaloelimina-tion. 

In the presence of a strong reductant such as titanium citrate, dithiothreitol, or sulfide, cofactor F430, and vitamin B12 can dechlorinate CT to either less chlorinated products (CF, DCM, and CM) or to completely non-chlorinated products as CO, C02, and formic acid at relatively high rates [262,390]. 

TCDD may be in a state of flux, resulting from dechlorination of octa-and hepta-CDD and being further dechlorinated to 2-mono-CDD [54]. Beside dechlorination reactions in sediments [4],dioxin dechlorination reactions have been demonstrated in the presence of microorganisms ([5, 12, 13, 431-433], dihydroxylated monoaromatic compounds [433], vitamin B12, and zero valent metals [3]. 

Assaf-Anid, N.,Nies, L. Vogel, T. M. (1992). Reductive dechlorination cf a polychlorinated biphenyl congener and hexachlorobenzene by vitamin B12. Applied and Environmental Microbiology, 58, 1057-60. 

In the presence of a strong reductant, abiotic reductive dechlorination of CPs is catalyzed by the reduced form of Vitamin B12 (Gantzer Wackett, 1991Smith Woods, 1994). These abiotic dechlorinations favor removal of m- and /(-chlorines, which differs substantially from reductive dechlorinations by anaerobic microbial consortia or by the CP-dehalogenating bacteria isolated to date. This indicates that abiotic dechlorinations of CPs are not central reactions in environmental or engineered anaerobic systems. 

Dolfing, J. (1995). Letter to the editor Regiospecificity of chlorophenol reductive dechlorination by Vitamin B12s. Applied and Environmental Microbiology, 6l, 2450-1. 

Burris, D.R., C.A. Delcomyn, M.H. Smith, and A.L. Roberts. 1996. Reductive dechlorination of tetrachloroethylene and trichloroethylene catalyzed by vitamin B12 in homogeneous and heterogeneous systems. Environ. Sci. Technol. 30, 3047-3052. 

The term reactive filtration may be used in a variety of applications. A simple search of the internet provides results such as reactive filter paper [1], adsorption filters for removing heavy metals from water [2], solid matrices used in organic synthesis [3], membranes for wastewater treatment, or even dialysis machines, filters for deep-frying pans and devices for the dechlorination of shower water by reaction with vitamin C. Most of the applications termed reactive filtration would be named heterogeneous catalysis or adsorption from a chemical engineer s point of view. 

Specific interactions with Ni (Wang et al. 2004) are reported to be at the base of the almost total conversion of CC14 to methane, thus suggesting that the preferred reaction path is not the sequential dechlorination, usually observed on other cathodes [e.g. Fe and glassy carbon (Liu et al. 2000 Costentin et al. 2003 Li et al. 2000)]. This is an important feature for the treatments based on permeable reactive barriers, because the intermediate species are also toxic and are much more slow reactants than carbon tetrachloride. A high yield in methane was also observed on vitamin B12 - modified silver electrode (Betterton et al. 1995). 

Rusling and coworkers have carried out extensive studies of the use of electrogenerated cobalt(I) complexes (including cobalt(I) salen, vitamin Bi2s, and cobalt(I) phthalo-cyanine) as catalysts both in homogeneous phase and in bicontinuous microemulsions [384] for the reductions of 1,2-dibromoethane and 1,2-dibromobutane [385], the debromi-nation of alkyl vicinal dibromides [386], the dechlorination of DDT [387], the reductions of 1-bromobutane, 1-bromododecane, and ran5-l,2-dibromocyclohexane [388,389], and the reduction of benzyl bromide [390]. 

In recent years more utilities have begun to use ascorbic acid (vitamin C) for dechlorination (23). Vitamin C has long been used in the medical field for dechlorination of tap water prior to use for kidney dialysis treatment. Vitamin C reacts with chlorine to produce chloride and dehydroascorbate. The reactions with chlorine and chloramine are shown below ... 

Ascorbic acid is reasonably stable in a dry state with a shelf life of about 1-3 yr (23). However, it rapidly oxidizes in solution. A 1% solution may remain at approx 80% potency after 10 d. A 0.02% solution will degrade to 0% within 3 d. Ascorbic acid is also currently available in tablet form for dechlorination applications. Release of ascorbic acid-containing waters under some conditions may reduce the pH of the receiving streams. Use of vitamin C is reported to have other potential benefits as it is an essential vitamin for healthy fish (23). Also, it can easily strip manganese oxide stains from reservoir surfaces and thereby promote better disinfection (once the vitamin C is exhausted). Vitamin C (ascorbic acid) is NSF certified, allowing it to be used in drinking water treatment to remove or reduce chlorine levels. 

Sodium sulfite is an odorless, solid white powder with a salty sulfurous taste that is soluble in water. It is a reducing agent that is used as a food preservative and antioxidant. Its use is prohibited in meats and other sources of vitamin Bj. Sodium sulfite is also used in the treatment of semichemical pulp in the paper industry, in the treatment of water, as a photographic developer, and in textile bleaching (antic-hlor). It has also found historical use in the water treatment field as a dechlorinating agent. 

Alkylation with benzyUc halides. Chloromethylated p-quinones couple with RAIMbj by (Ph3P)2Ni which is obtained from dechlorination of the complexed nickel chloride with BuLi." An expeditious route to vitamins Kj and K2 is based on this method. 

The reductive dechlorination of hexa- and pentachlorobenzene has been demonstrated to be mediated by vitamin B,2 and hematin (Gantzer and Wackett, 1991). 

Some reactions, e.g., the electrolytic dechlorination of DDT, can be carried out in bicontinuous ionic microemulsions in a less expensive and less toxic approach than the conventional process [121]. The kinetics rate of electrogenerated macrocyclics like vitamin B-12 can be controlled in a bicontinuous cationic microemulsion [122]. 

The biochemistry tmderlying reductive dechlorination was recently examined in vitro using a series of transition-metal coenzymes and other biochemical reductants [49]. Vitamin and coenzyme F... 

The synthesis of enynes is of interest in the chemistry of certain natural products. Terminal enynes occur in several natural products such as histrionicotoxin and laurencin, and the internal enyne unit is found along with polyacetylenes and allenes in natural products from Compositae and Umbelliferae. Both internal Z-and. E-enynes are also useful as precursors to stereochemically define d dienes on their partial reduction. A group from Phillips-Duphar has described an efficient synthesis of the functionalized enyne (95), which serves as the C5 synthon for the convergent synthesis of vitamin A. The l,3-dichloro-2-ether (94) is dechlorinated, substituted, and isomerized in one step on reaction with two molar equivalents of sodium acetylide in liquid ammonia, giving (95) with an E Z ratio... 

The minimal salt medium was fed at a 4 day HRT and amended with 3 mM TCE, 2 mM lactate, 15 mM methanol, 5 mL L ATTC MD-VS vitamin supplement and 500 mg L Vitamin B12. A mixture of cysteine and sodium sulphide was used as a reducing agent, sodium bicarbonate was used as a buffer (pH 6.5 to 7.5) and temperature was kept at 30°C. No was added. Over 120 days, reductive dechlorination of TCE was sustained at influent concentrations of 1 and 2 mM, with 97% converted to ethene. The Dehalococcoides biomass concentration reached 10 cells E ... 

Vitamin B12 195 has also been used as a catalyst for the abiotic dechlorination of perchloroethylene (PCE) to... 

The dechlorination of chlorinated alkenes could also be performed by porphyrin cobalt complex such as 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin cobalt ((TCPP)-Co). This cobalt complex, structurally similar to vitamin B12, was found to have superior aqueous-phase dechlorination activity on chlorinated ethylenes relative to vitamin Bi2. Based on fully detailed parameters dependence, the authors suggest the catalytic cycle below.This methodology has been used to synthesize C-labeled air-DCE from TCE (Scheme 33). ... 

Dechlorination of alkyl chlorides such as chloroacetonitrile by vitamin B12 has also been observed to take place. 

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