Carbon tetrachloride
| Carbon tetrachloride | |||
|---|---|---|---|
| Structural formula of carbon tetrachloride | Space-filling model carbon tetrachloride | ||
| Tetrachloromethane | |||
| Other names Tetrachloromethane, Benziform, Benzinoform, Carbon chloride, Carbon tet, Freon 10, Halon 104, Methane tetrachloride, Perchloromethane, Tetraform, Tetrasol | |||
| Identifiers | |||
| CAS number | 56-23-5 7px | ||
| PubChem | 5943 | ||
| ChemSpider | 5730 7px | ||
| UNII | CL2T97X0V0 7px | ||
| EC number | 200-262-8 | ||
| UN number | 1846 | ||
| KEGG | C07561 7px | ||
| ChEBI | CHEBI:27385 7px | ||
| ChEMBL | CHEMBL44814 7px | ||
| RTECS number | FG4900000 | ||
| Jmol-3D images | Image 1 | ||
| |||
| Molecular formula | CCl4 | ||
| Molar mass | 153.82 g mol−1 | ||
| Structure | |||
| Crystal structure | Monoclinic | ||
| Molecular shape | Tetrahedral | ||
| Hazards | |||
| MSDS | ICSC 0024
|
EU Index | 602-008-00-5 |
| EU classification | Carc. Cat. 3 Toxic (T) Dangerous for the environment (N) | ||
| R-phrases | R23/24/25, R40, R48/23, R59, R52/53 | ||
| S-phrases | (S1/2), S23, S36/37, S45, S59, S61 | ||
| NFPA 704 | |||
| Flash point | Not flammable | ||
| Autoignition temperature |
982 °C | ||
| LD50 | 2350 mg/kg | ||
| Thermochemistry | |||
| Std enthalpy of formation ΔfH |
−135 kJ·mol−1 | ||
| Standard molar entropy S |
216 J·mol−1·K−1 | ||
| Related compounds | |||
| Other cations | Silicon tetrachloride Germanium tetrachloride Tin tetrachloride Lead tetrachloride | ||
| Related chloromethanes | Chloromethane Dichloromethane Chloroform | ||
| Related compounds | Tetrafluoromethane Tetrabromomethane Tetraiodomethane | ||
| 14px (verify) (what is: 10px/10px?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |||
| Infobox references | |||
Carbon tetrachloride, also known by many other names (the most notable being carbon tet in the cleaning industry, and as Halon or Freon in HVAC; see Table for others) 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.
Contents
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.[1]
Carbon tetrachloride was originally synthesised by the French chemist Henri Victor Regnault in 1839 by the reaction of chloroform with chlorine,[2] but now it is mainly produced from methane:
- CH4 + 4 Cl2 → CCl4 + 4 HCl
The production often utilizes by-products of other chlorination reactions, such as from the syntheses of dichloromethane and chloroform. Higher chlorocarbons are also subjected to "chlorinolysis:"
- C2Cl6 + Cl2 → 2 CCl4
Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C:[1]
Properties
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 with a smell characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene smell reminiscent of dry cleaners' shops.
Solid tetrachloromethane has 2 polymorphs: crystalline II below −47.5 °C (225.6 K) and crystalline I above −47.5 °C.[3]
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°.[4] With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilled in the environment.
Uses
In the 20th century, carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in lava lamps.[5]
In 1910, The Pyrene Manufacturing Company of Delaware filed a patent for a using carbon tetrachloride to extinguish fires.[6] The liquid vaporized and extinguished the flames by inhibiting the chemical chain reaction of the combustion process (it was an early 20th-century presupposition that the fire suppression ability of carbon tetrachloride relied on oxygen removal.) In 1911, they patented a small, portable extinguisher that used the chemical.[7] This consisted of a brass bottle with an integrated handpump that was used to expel a jet of liquid toward the fire. As the container was unpressurized, it could be easily refilled after use.[8] Carbon tetrachloride was suitable for liquid and electrical fires and the extinguisers were often fitted to motor vehicles.
One specialty use of carbon tetrachloride was in Stamp collecting, to reveal Watermarks on postage stamps without damaging them. 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 seen.
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. This reaction also caused a rapid depletion of oxygen. 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.
Carbon tetrachloride is one of the most potent hepatotoxins (toxic to the liver), and is widely used in scientific research to evaluate hepatoprotective agents.[9][10]
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 (these conditions are known as Wohl-Ziegler Bromination).
In organic chemistry, carbon tetrachloride serves as a source of chlorine in the Appel reaction.
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 in general chemists try to replace it with other solvents.[9] 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.[11] Its use has been largely superseded by deuterated solvents. Use of carbon tetrachloride in determination of oil has been replaced by various other solvents, such as tetrachloroethylene.[9]
Safety
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).[18]
Like many other volatile substances, carbon tetrachloride is prone to misuse by inhalation, due to its possible depressant and/or dissociative effect upon the central nervous system. Use of carbon tetrachloride in this manner presents serious health risks, and may result in toxic effects described above.
Carbon tetrachloride is also both ozone-depleting[19] and a greenhouse gas.[20] However, since 1992[21] its atmospheric concentrations have been in decline for the reasons described above (see also the atmospheric time-series figure). CCl4 has an atmospheric lifetime of 85 years.[22]
References
- ↑ 1.0 1.1 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
- ↑ V. Regnault (1839) "Sur les chlorures de carbone CCl et CCl2 " (On the chlorides of carbon CCl and CCl2 ), Annales de Chimie et de Physique, vol. 70, pages 104-107. Reprinted in German as: Script error
- ↑ Carbon tetrachloride
- ↑ F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. Chemicke tabulky anorganickych sloucenin (Chemical tables of inorganic compounds). SNTL, 1986.
- ↑ Script error
- ↑ U.S. Patent 1,010,870, filed April 5, 1910.
- ↑ U.S. Patent 1,105,263, filed Jan 7, 1911.
- ↑ "Pyrene Fire Extinguishers". Vintage Fire Extinguishers. http://www.vintagefe.com/pyrene.html. Retrieved 23 December 2009.
- ↑ 9.0 9.1 9.2 Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003.
- ↑ 10.0 10.1 Script error
- ↑ W. Reusch. "Introduction to Nuclear Magnetic Resonance Spectroscopy". Virtual Textbook of Organic Chemistry. Michigan State University. http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/nmr/nmr1.htm.
- ↑ Script error
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- ↑ Script error[dead link]
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- ↑ Material Safety Data Sheet, Carbon tetrachloride at Fisher Scientific
- ↑ Script error
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- ↑ Script error
- ↑ The Atlas of Climate Change (2006) by Kirstin Dow and Thomas E. Downing ISBN 978-0-520-25558-6
External links
- International Chemical Safety Card 0024
- NIOSH Pocket Guide to Chemical Hazards 0107
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- 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
- Script error|
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- Substance profile at ntp.niehs.nih.gov
- ChemSub Online: Carbon tetrachloride.
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