Reduction of carbon tetrachloride

Methylene chloride CHjCl, b.p. 41°, is obtained as a by product in the com mercial preparation of chloroform by the reduction of carbon tetrachloride with moist iron and also as one of the products in the chlorination of methane it is a useful extraction solvent completely immiscible with water. 

FIGURE 5.5 P450-mediated reduction of carbon tetrachloride and subsequent reactions of the trichloromethyl radical. 

A one-electron reduction of the bond between an aliphatic carbon and a halogen leads to a halogen anion and a carbon-free radical. A good example is the reduction of carbon tetrachloride as discussed earlier in this chapter. The first product in the reduction is the trichloromethyl-free radical. Carbon-centered radicals are not very reactive with biological molecules, but they react very rapidly with molecular oxygen (a diradical) to form a peroxy-free radical (Fig. 5.15), which is quite toxic (10). 

Butler TC. 1961. Reduction of carbon tetrachloride in vivo and reduction of carbon tetrachloride and chloroform in vitro by tissues and tissue constituents. J Pharmacol Exp Ther 134 311-319. 

In aprotic solvents, the carbanions, generated by reduction of carbon tetrachloride or ethyl trichloroacetate at mercury, can be trapped by reaction with an added carbonyl compound [74], This reaction has been developed as a useful step in synthesis. Cathodic reduction of a system containing a catalytic amount of carbon tetrachloride, excess chloroform and an aldehyde leads to an effective ionic chain reaction sustained by trichlormethyl carbanions as indicated in Scheme 4.4. A carbon-felt cathode is used with diraethylformamide as solvent [75]. Aldehydes react with cuiTent efficiency of 700 %, which indicates a short chain reaction. Ketones... 

When no electrophile is present, reduction of carbon tetrachloride leads to di-chlorocarbene by elimination of chloride ion from the trichloromethyl carbanion intermediate. Dichloromethane is the best solvent for this process [79], The car-bene is trapped by reaction with an alkene to form a dichlorocyclopropane (Table... 

Balko, B.A. Clarkson, K.M. (2001) The effect of doping with Ti(lV) and Sn(IV) on oxygen reduction at hematite electrodes. J. Electro-chem. Soc. 148 E85-E91 Balkwill, D. Maratea, D. Blakemore, R.P. (1980) Ultrastructure of a magnetotactic spirillum. J. Bacteriol. 141 1399-1408 Ballko, B.A. Tratnyek, P.G. (1998) Photoeffects on the reduction of carbon tetrachloride by zero-valent iron. J. Phys. Chem. B 102 1459-1465... 

F. (2000) Dissimilatory iron-reducing bacteria can influence the reduction of carbon tetrachloride by iron metal. Environ. Sd. Techn. 34 2461-2464... 

The formation of active carbanion species and their addition to electrophiles have also been observed in the cathodic reduction of carbon tetrachloride and trichloroacetic acid ester 34), though yields are not always satisfactory. 

Under this heading a few borderline cases between direct and indirect electrochemical reactions can be included. Dihalocarbenes are probably intermediates in the cathodic reduction of certain polyhalogenated compounds172) as an example, cathodic reduction of carbon tetrachloride at a mercury cathode in acetonitrile-tetrabutylammonium bromide in the presence of tetramethylethylene gave a low yield of l,l-dichloro-2,2,3,3-tetramethylcyclopropane ... 

Balko BA, Tratnyek PG. Photoeffects on the reduction of carbon tetrachloride by zero-valent iron. J Phys Chem B 1998 102 1459-1465. 

Moenig, J. Bahnemann, D. Asmus, K. D. One electron reduction of carbon tetrachloride in solutions a trichloromethyldioxy-free radical mediated, Chem. Biol. Interact. 1983, 47, 15. 

Wang, J., Blowers, P. and Farrell, J. (2004) Understanding reduction of carbon tetrachloride at nickel surfaces. Environ. Sci. Technol. 38, 1576-1581. 

Metal carbonyls like Mo(CO)s or Mn2(CO)io will catalyze the reduction of carbon tetrachloride to chloroform by isopropyl alcohol. Apparently these are radical reactions initiated by abstraction of a chloride from carbon tetrachloride by the metal complex. ... 

The initially formed l-chloro-2,2,2-trifluoroethyl radical may also canse a radical attack of polyunsaturated lipids, which produces l-chloro-2,2,2-trifluoroethane. This mechanism is similar to the pathway described with the trichlo-romethyl radical formed during the one-electron reduction of carbon tetrachloride (Eigure 33.14). The trichloromethyl radical may initiate a peroxidation of unsaturated lipids from the membrane with subsequent liberation of chloroform. 

Nanocrystalline boron carbide (B4C) with a partide size of approximatdy 15-40 nm was synthesized by Gu et al. [145] via a solvothermal reduction of carbon tetrachloride in the presence of amorphous boron powder at 600 °C in an autoclave, using metallic lithium as the reductant. 

Chloroform is produced by reaction of chlorine with ethanol and by the reduction of carbon tetrachloride with moist iron. It was once used as a general anesthetic in surgery but has been replaced by less toxic, safer anesthetics, such as ether. Chloroform is produced as a byproduct of water, sewage, and wood pulp chlorination. 

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