56-23-5 tetrachloromethane

The degradation of tetrachloromethane by Pseudomonas stutzeri strain KC involves hydrolysis to CO2 by a mechanism involving the natnrally prodnced pyridine-2,6-dithiocarboxylic acid (Lewis et al. 2001) details have already been discnssed in Chapter 7, Part 3. This organism was nsed in field evaluation at a site at which the indigenons flora was ineffective, and acetate was used as electron donor (Dybas et al. 2002). One novel featnre was inocnlation at a series of wells perpendicnlar to the established flow of the gronndwater plnme. Effective removal of tetrachloromethane was snstained over a period of 4 years, and transient levels of chloroform and H2S disappeared after redncing the concentration of acetate. 

TCE is not able to support the growth of a single organism, but it is susceptible to cooxidation by oxygenases elaborated by organisms dnring growth with structurally unrelated substrates. A review of methanotrophic bacteria (Hanson and Hanson 1996) contains a useful account of their application to bioremediation of TCE-contaminated sites. 

mendocina KR-1 carries out para hydroxylation, and Ralstonia Pseudomonas) pickettii carries out para hydroxylation, although it was originally reported to carry out meta hydroxylation. 

The complexity introduced by exposure of an established mixed culture growing with a single substrate to an alternative cosubstrate is illustrated by the following. A stable mixed culture of Pseudomonas putida mt-2, P. putida FI, P. putida GJ31, and Burkholderia cepacia G4 growing with limited concentrations of toluene was established. Exposure to TCE for a month resulted in the loss of viability of the last three organisms, and resulted in a culture dominated by P. putida mt-2 from which mutants had fortuitously arisen (Mars et al. 1998). 

Two different types of experiments on bioremediation of sites contaminated with TCE have been carried out, and have been preceded by, and taken advantage of the valuable results obtained in microcosm experiments. 

Although the employment of tetrachloromethane (carbon tetrachloride) in fire extinguishers has now largely been superseded by more efficient and inherently safer materials, this type of extinguisher is undoubtedly still in use, despite the fact that phosgene is a major product of its oxidative thermal decomposition. 

In real-fire situation experiments, in which commercial CCl, extinguishers were used to extinguish fires contained in closed rooms (28 m capacity), phosgene is said to be generated in lethal concentrations [649b]. At the industrial threshold limit concentration of 

In the high temperatures of a carbon monoxide flame (up to 1730 C), CCI., vapours in dry air were completely decomposed, but only a low concentration of COCij (0.07 p.p.m.) was detected [1527]. Higher concentrations of COCIj were obtained when CCi was poured onto a red-hot iron block [649b], or onto burning magnesium [1600]. 

Experiments conducted with pure CCl in dry air at 800 C indicated that phosgene is formed according to [649b]  

In real fire situations, phosgene may also result from the thermal hydrolysis of tetrachloromethane [649b]  

---

Halogen derivatives of silanes can be obtained but direct halogena-tion often occurs with explosive violence the halogen derivatives are usually prepared by reacting the silane at low temperature with a carbon compound such as tetrachloromethane, in the presence of the corresponding aluminium halide which acts as a catalyst. 

The gas phase chlorination of methane is a reaction of industrial importance and leads to a mixture of chloromethane (CH3CI) dichloromethane (CH2CI2) trichloromethane (CHCI3) and tetrachloromethane (CCI4) by sequential substitution of hydrogens... 

One of the chief uses of chloromethane is as a starting material from which sili cone polymers are made Dichloromethane is widely used as a paint stripper Trichloromethane was once used as an inhalation anesthetic but its toxicity caused it to be replaced by safer materials many years ago Tetrachloromethane is the starting mate rial for the preparation of several chlorofluorocarbons (CFCs) at one time widely used as refrigerant gases Most of the world s industrialized nations have agreed to phase out all uses of CFCs because these compounds have been implicated m atmospheric processes that degrade the Earth s ozone layer... 

Methane reacts with CI2 to give chloromethane dichloromethane trichloromethane and tetrachloromethane... 

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6]-, 1,1-dichloroethane cis- and /n j -l,2-dichloroethylenes [156-59-2 and 156-60-5]-, 1,1-dichloroethylene [75-35-4] (vinyhdene chloride) 2-chloroethanol [107-07-3]-, ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5])-, and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of soflds which can foul and clog operating lines and controls (78). 

Chlorination of various hydrocarbon feedstocks produces many usehil chlorinated solvents, intermediates, and chemical products. The chlorinated derivatives provide a primary method of upgrading the value of industrial chlorine. The principal chlorinated hydrocarbons produced industrially include chloromethane (methyl chloride), dichloromethane (methylene chloride), trichloromethane (chloroform), tetrachloromethane (carbon tetrachloride), chloroethene (vinyl chloride monomer, VCM), 1,1-dichloroethene (vinylidene chloride), 1,1,2-trichloroethene (trichloroethylene), 1,1,2,2-tetrachloroethene (perchloroethylene), mono- and dichloroben2enes, 1,1,1-trichloroethane (methyl chloroform), 1,1,2-trichloroethane, and 1,2-dichloroethane (ethylene dichloride [540-59-0], EDC). 

Carbon tetrachloride [56-23-5] (tetrachloromethane), CCl, at ordinary temperature and pressure is a heavy, colorless Hquid with a characteristic nonirritant odor it is nonflammable. Carbon tetrachloride contains 92 wt % chlorine. When in contact with a flame or very hot surface, the vapor decomposes to give toxic products, such as phosgene. It is the most toxic of the chloromethanes and the most unstable upon thermal oxidation. The commercial product frequendy contains added stabilizers. Carbon tetrachloride is miscible with many common organic Hquids and is a powerhil solvent for asphalt, benzyl resin (polymerized benzyl chloride), bitumens, chlorinated mbber, ethylceUulose, fats, gums, rosin, and waxes. 

Figure 2.25. H NMR spectra of methanol (36, a) and hexafluoroacetylacetone (37, b), both in the pure state (above) and diluted in tetrachloromethane solution (5%, below) [25 °C, 90 MHz, CW recording]...

Tetrachloroethylene, see Perchloroethylene Tetrachloromethane, see Carbon tetrachloride Tetrahydrofuran 9.2 9.75 0.47 0.2... 

Tetrachloroethane Tetrachloroethylene (perchloroethylene) Tetrachloromethane (carbon tetrachloride) Tetrachloronaphthalene... 

Dichloromethane, trichloromethane, and tetrachloromethane are widely known by their common names methylene chloride, chloroform, and carbon tetrachloride, respectively. 

If the alkyl halide contains more than one, equally reactive C-halogen centers, these will generally react each with one aromatic substrate molecule. For example dichloromethane reacts with benzene to give diphenylmethane, and chloroform will give triphenylmethane. The reaction of tetrachloromethane with benzene however stops with the formation of triphenyl chloromethane 7 (trityl chloride), because further reaction is sterically hindered ... 

---