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Carbon tetrachloride, also known by many other names (see Table) is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent. It is a colourless liquid with a “sweet” smell that can be detected at low levels.
Both carbon tetrachloride and tetrachloromethane are acceptable names under IUPAC nomenclature. Colloquially, it may be called “carbon tet”.
 History and synthesis
The production of carbon tetrachloride has steeply declined since the 1980s due to environmental concerns and the decreased demand for CFCs, which were derived from carbon tetrachloride. In 1992, production in the U.S.-Europe-Japan was estimated at 720,000 tonnes.
- CH4 + 4 Cl2 → CCl4 + 4 HCl
- C2Cl6 + Cl2 → 2 CCl4
In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetrical geometry, CCl4 is non-polar. Methane gas has the same structure, making carbon tetrachloride a halomethane. As a solvent, it is well suited to dissolving other non-polar compounds, fats and oils. It can also dissolve iodine. It is somewhat volatile, giving off vapors having a smell characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene smell reminiscent of dry cleaners‘ shops.
In 1910, The Pyrene Manufacturing Company of Delaware filed a patent for a using carbon tetrachloride to extinguish fires. The liquid vaporized and extinguished the flames by creating a dense, oxygen-excluding blanket of fumes, and to a lesser extent, inhibiting the chemical reaction of combustion. A carbon tetrachloride fire extinguisher was patented in 1911 – this took the form of a brass bottle with a hand pump to expel a jet of liquid.. Such extinguishers were commonly used until the mid-20th century.
One specialty use of “carbon tet” was by stamp collectors to reveal watermarks on the backs of postage stamps. A small amount of the liquid was placed on the back of a stamp sitting in a black glass or obsidian tray. The letters or design of the watermark could then be clearly detected.
However, once it became apparent that carbon tetrachloride exposure had severe adverse health effects, safer alternatives such as tetrachloroethylene were found for these applications, and its use in these roles declined from about 1940 onward. The fact that high temperatures cause it to react to produce Phosgene made it especially hazardous when used against fires. Carbon tetrachloride persisted as a pesticide to kill insects in stored grain, but in 1970, it was banned in consumer products in the United States.
Prior to the Montreal Protocol, large quantities of carbon tetrachloride were used to produce the freon refrigerants R-11 (trichlorofluoromethane) and R-12 (dichlorodifluoromethane). However, these refrigerants are now believed to play a role in ozone depletion and have been phased out. Carbon tetrachloride is still used to manufacture less destructive refrigerants. Carbon tetrachloride has also been used in the detection of neutrinos.
Because it has no C-H bonds, carbon tetrachloride does not easily undergo free-radical reactions. Hence it is a useful solvent for halogenations either by the elemental halogen, or by a halogenation reagent such as N-bromosuccinimide.
It is used as a solvent in synthetic chemistry research, but because of its adverse health effects, it is no longer commonly used, and chemists generally try to replace it with other solvents. It is sometimes useful as a solvent for infrared spectroscopy because there are no significant absorption bands > 1600 cm−1. Because carbon tetrachloride does not have any hydrogen atoms, it was historically used in proton NMR spectroscopy. However, carbon tetrachloride is toxic, and its dissolving power is low. Its use has been largely superseded by deuterated solvents, which offer superior solvating properties and allow for deuterium lock by the spectrometer[clarification needed]. Use of carbon tetrachloride in determination of oil has been replaced by various other solvents.
Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system, degenerate the liver and kidneys and may result (after prolonged exposure) in coma and even death. Chronic exposure to carbon tetrachloride can cause liver and kidney damage and could result in cancer. More information can be found in Material safety data sheets.
In 2008, a study of common cleaning products found the presence of carbon tetrachloride in “very high concentrations” (up to 101 mg m−3) as a result of manufacturers’ mixing of surfactants or soap with sodium hypochlorite (bleach).
Carbon tetrachloride is also both ozone-depleting and a greenhouse gas. However, since 1992 its atmospheric concentrations have been in decline for the reasons described above (see also the atmospheric time-series figure).
- ^ a b Manfred Rossberg, Wilhelm Lendle, Gerhard Pfleiderer, Adolf Tögel, Eberhard-Ludwig Dreher, Ernst Langer, Heinz Jaerts, Peter Kleinschmidt, Heinz Strack, Richard Cook, Uwe Beck, Karl-August Lipper, Theodore R. Torkelson, Eckhard Löser, Klaus K. Beutel, “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry, 2006 Wiley-VCH, Weinheim.doi:10.1002/14356007.a06_233.pub2
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- ^ Carbon tetrachloride
- ^ F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. Chemicke tabulky anorganickych sloucenin (Chemical tables of inorganic compounds). SNTL, 1986.
- ^ Doherty RE (2000). “A History of the Production and Use of Carbon Tetrachloride, Tetrachloroethylene, Trichloroethylene and 1,1,1-Trichloroethane in the United States: Part 1—Historical Background; Carbon Tetrachloride and Tetrachloroethylene”. Environmental Forensics 1 (1): 69–81. doi:10.1006/enfo.2000.0010.
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 External links
- International Chemical Safety Card 0024
- NIOSH Pocket Guide to Chemical Hazards 0107
- “Carbon Tetrachloride (Group 2B)”. International Agency for Research on Cancer (IARC) – Summaries & Evaluations 71: 401. 1999. http://www.inchem.org/documents/iarc/vol71/011-carbontetrac.html.
- IARC Monograph: “Carbon Tetrachloride”
- Toxicological profile for carbon tetrachloride
- Environmental health criteria for carbon tetrachloride
- Carbon tetrachloride MSDS at Hazardous Chemical Database
- MSDS at Oxford University
- Egli C, Tschan T, Scholtz R, Cook AM, Leisinger T (November 1988). “Transformation of tetrachloromethane to dichloromethane and carbon dioxide by Acetobacterium woodii“. Appl. Environ. Microbiol. 54 (11): 2819–24. PMID 3145712. PMC 204379. http://aem.asm.org/cgi/pmidlookup?view=long&pmid=3145712. |
- Picardal FW, Arnold RG, Couch H, Little AM, Smith ME (November 1993). “Involvement of cytochromes in the anaerobic biotransformation of tetrachloromethane by Shewanella putrefaciens 200“. Appl. Environ. Microbiol. 59 (11): 3763–70. PMID 8285682. PMC 182529. http://aem.asm.org/cgi/pmidlookup?view=long&pmid=8285682.
- Substance profile at ntp.niehs.nih.gov
Inorganic carbon compounds