Carbon tetrachloride

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Carbon tetrachloride
IUPAC name Carbon tetrachloride
Tetrachloromethane
Other names Benziform, Carbon chloride, Methane tetrachloride, Perchloromethane, Carbon tet, Benzinoform, Tetraform, Tetrasol, Freon 10, Halon 104, UN 1846
Identifiers
3D model (JSmol)
ChEBI
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KEGG
RTECS number FG4900000
Properties
CCl4
Molar mass 153.82 g/mol
Appearance Colorless liquid
Density 1.5842 g/cm3, liquid

1.831 g.cm-3 at -186 °C (solid)
1.809 g.cm-3 at -80 °C (solid)

Melting point
Boiling point
log P 2.64
Vapor pressure 11.94 kPa at 20 °C
kH 365 kJ.mol-1 at 24.8 °C
Structure
Crystal structure Monoclinic
Molecular shape Tetrahedral
Hazards
EU classification {{{value}}}
S-phrases (S1/2), S23, S36/37, S45, S59, S61
Flash point {{{value}}}
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

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Overview

Carbon tetrachloride, also known by many other names (see Table) is the chemical compound with the formula CCl4. It is a reagent in synthetic chemistry and was formerly widely used in fire extinguishers and as a precursor to refrigerants. It is a colorless liquid with a "sweet" smell that can be detected at low levels.

Both carbon tetrachloride and tetrachloromethane are acceptable names under IUPAC nomenclature, depending on whether it is seen as an inorganic or an organic compound. Colloquially, it is called "carbon tet".

Production

Carbon tetrachloride was originally synthesised in 1839 by reaction of chloroform with chlorine, but the most common synthesis is now chlorination of carbon disulfide at 105 to 130 °C:

CS2 + 3Cl2 → CCl4 + S2Cl2

CCl4 can also be prepared from methane via the reaction:

CH4 + 4 Cl2 → CCl4 + 4HCl

It is also a byproduct in the synthesis of dichloromethane and chloroform.

Properties

In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a carbon atom, in the center, by single covalent bonds. Because of this symmetrical geometry, the molecule has no net dipole moment; that is, CCl4 is non-polar. As a solvent, it is well suited to dissolving other non-polar compounds, fats and oils. 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.

Solid tetrachloromethane has 2 allotropes: crystaline II below -47.5 °C (225.6 K) and crystaline I above -47.5 °C.[1]

At -47.3 °C it has monoclinic crystal structure with space group C2/c and lattice constants a = 20.3, b = 11.6, c = 19.9 (.10-1 nm), β = 111°.[2]

Uses

In the early 20th century, carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in fire extinguishers[3]. 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. 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.

Reactivity

Carbon tetrachloride has practically no flammability at lower temperatures. Under high temperatures in air, it forms poisonous phosgene.

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.

In organic chemistry, carbon tetrachloride serves as a source of chlorine in the Appel reaction.

As a solvent

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 substitute 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[4]. Its use has been largely superseded by deuterated solvents, which offer superior solvating properties and allow for deuterium lock by the spectrometer.

Safety

Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system, degenerate the liver[5] and kidneys[6] and may result (after prolonged exposure) in coma and even death[7]. Chronic exposure to carbon tetrachloride can cause liver[8][9] and kidney damage and could result in cancer[10] More information can be found in Material safety data sheets.

Carbon tetrachloride is also both ozone-depleting[11] and a greenhouse gas[12]. However, since 1992[13] its atmospheric concentrations have been in decline for the reasons described above (see also the atmospheric time-series figure).

File:AYool CCl4 history.png
Time-series of atmospheric concentrations of CCl4 (Walker et al., 2000).

See also

References

  1. http://webbook.nist.gov/cgi/cbook.cgi?ID=C56235&Units=SI&Mask=4#Thermo-Phase
  2. F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. Chemicke tabulky anorganickych sloucenin (Chemical tables of inorganic compounds). SNTL, 1986.
  3. Doherty R. E. (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" (1): 69–81. doi:10.1006/enfo.2000.0010.
  4. Introduction to Nuclear Magnetic Resonance Spectroscopy, Michigan State University
  5. WF Seifert, A Bosma, A Brouwer, HF Hendriks, PJ (1994). "Vitamin A deficiency potentiates carbon tetrachloride-induced liver fibrosis in rats". Hepatology. 19: 193–201. Text " issue 1 " ignored (help)
  6. Liu KX, Kato Y, Yamazaki M, Higuchi O, Nakamura T, Sugiyama Y. (1993). "Decrease in the hepatic clearance of hepatocyte growth factor in carbon tetrachloride-intoxicated rats". Hepatology. 17: 651–60. Text " issue 4 " ignored (help)
  7. Recknagel R.O., Glende E.A., Dolak J.A., Waller R.L. (1989). "Mechanism of Carbon-tetrachloride Toxicity". Pharmacology Therapeutics (43): 139–154. doi:10.1016/0163-7258(89)90050-8.
  8. Recknagel RO (1967). "Carbon tetrachloride Hepatotoxicity". Pharmacological Reviews. 19 (2): 145.
  9. Masuda Y (2006). "Learning toxicology from carbon tetrachloride-induced hepatotoxicity". Yakugaku Zasshi -Journal of the Pharmaceutical Society of Japan. 126 (10): 885–899.
  10. Rood AS, McGavran PD, Aavenson JW; et al. (2001). "Stochastic estimates of exposure and cancer risk from carbon tetrachloride released to the air from the Rocky Flats Plant". Risk Analysis. 21 (4): 675–695.
  11. Fraser P. (1997). "Chemistry of stratospheric ozone and ozone depletion". Australian Meteorological Magazine. 46 (3): 185–193.
  12. Evans WFJ, Puckrin E (1996). "A measurement of the greenhouse radiation associated with carbon tetrachloride (CCl4)". Geophysical Research Letters. 23 (14): 1769–1772.
  13. Walker, S. J., R. F. Weiss & P. K. Salameh (2000). "Reconstructed histories of the annual mean atmospheric mole fractions for the halocarbons CFC-11, CFC-12, CFC-113 and carbon tetrachloride". Journal of Geophysical Research. 105: 14285–14296.

External links

cs:Tetrachlormethan da:Tetraklorkulstof de:Tetrachlormethan id:Karbon tetraklorida it:Tetracloruro di carbonio lv:Tetrahlorogleklis lt:Anglies tetrachloridas hu:Szén-tetraklorid nl:Tetrachloormethaan sk:Tetrachlórmetán fi:Hiilitetrakloridi sv:Koltetraklorid uk:Тетрахлорметан



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