Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also recognised by the IUPAC), is an organic compound with the chemical formula CCl4. It is a volatile, non-flammable, dense, colourless liquid with a chloroform-like sweet odour that can be detected at low levels. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, an anthelmintic and a cleaning agent, but has since been phased out because of environmental and safety concerns. Exposure to high concentrations of carbon tetrachloride can affect the central nervous system and degenerate the liver and kidneys. Prolonged exposure can be fatal.
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.Smith, Michael, March, Jerry (2007). March’s Advanced Organic Chemistry : Reactions, Mechanisms, and Structure. 6th ed. Hoboken, N.J.: John Wiley & Sons. pp. 25-26 Because of this symmetric geometry, CCl4 is non-polar. Methane () has the same structure, making carbon tetrachloride a halomethane. As a solvent, it is well suited to dissolving other non-polar compounds such as fats and oils. It can also dissolve iodine. Carbon tetrachloride is miscible with organic solvents such as acetone, acetylacetone, aniline, benzaldehyde, benzene, benzyl alcohol, 1-butanol, butyl acetate, diethyl ether, ethanol, isoamyl alcohol, methyl isobutyl ketone, nitromethane, and pyridine; however, carbon tetrachloride is insoluble in diacetone alcohol, diethanolamine, ethylene glycol, formamide, glycerol, hydroxyethyl-ethylenediamine, and 1,3-propanediol.Weast, Robert C. (1973). "Miscibility of Organic Solvent Pairs". CRC Handbook of Chemistry and Physics (54th ed.). Ohio, USA: CRC Press. page C-720. It is volatile, giving off vapors with an odor characteristic of other chlorinated solvents.
Solid carbon tetrachloride has two polymorphs: crystalline II below −47.5°C (225.6 K) and crystalline I above −47.5°C. 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°.F. Brezina, J. Mollin, R. Pastorek, Z. Sindelar. Chemicke tabulky anorganickych sloucenin (Chemical tables of inorganic compounds). SNTL, 1986.
With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilt in the environment.
Reactions Despite being generally inert, carbon tetrachloride can undergo various reactions. Hydrogen or an acid in the presence of an iron catalyst can reduce carbon tetrachloride to chloroform, dichloromethane, chloromethane and even methane. When its vapours are passed through a red-hot tube, carbon tetrachloride dechlorinates to tetrachloroethylene and hexachloroethane."Carbonic Dichloride". Tidy, C. M. (1887). Handbook of modern chemistry, inorganic and organic. UK: Smith, Elder & Company. p. 215
Carbon tetrachloride, when treated with HF, gives various compounds such as trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12), chlorotrifluoromethane (R-13) and carbon tetrafluoride with HCl as the by-product:
This was once one of the main uses of carbon tetrachloride, as R-11 and R-12 were widely used as refrigerants.
An alcohol solution of potassium hydroxide decomposes it to potassium chloride and potassium carbonate in water:Wislicenus, J., Strecker, A., Hodgkinson, W. R. E. (1882). Adolph Strecker's Short Text-book of Organic Chemistry. USA: D. Appleton.
Carbon is sufficiently oxophilic that many compounds react to give phosgene:
Reactants Products Conditionscite → 350°C → → → → ZnO dry; 200°CWatts, H. (1872). A Dictionary of Chemistry. UK: Longman, Green, Roberts & Green.
Reaction with hydrogen sulfide gives thiophosgene:Graham-Otto's ausführliches Lehrbuch der Chemie. (1881). Germany: Vieweg.
History and synthesis Carbon tetrachloride was first obtained by the French chemist Henri Victor Regnault around 1839 from carbon compounds such as chloroform and methanol with abundant chlorine. Regnault added chlorine to chloroform under sunlight and separated the resulting liquid from chloroform by distillation. He noted the density of the liquid as 1.599 g/cm3 and its boiling point as 78 °C. He analyzed the elemental composition of the compound; he calculated that it consisted of 92.05% chlorine and 7.95% carbon. He found the vapor density to be 5.302.Regnault, Henri Victor (1839). "De l'Action du Chlore sur les Éthers Hydrochloriques de l'alcool et de l'esprit de bois, et de plusieurs points de la Théorie des Éthers: Troisième produit de l'action du chlore sur l'éther hydrochlorique de l'esprit de bois. Éther hydrochlorique perchloruré". Annales de Chimie et de Physique. vol 71. p. 383-385.
Hermann Kolbe made carbon tetrachloride in 1843 by passing chlorine over carbon disulfide through a porcelain tube.Graham, T., Watts, H. (1850). Elements of Chemistry: Including the Applications of the Science in the Arts. USA: Baillière. Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C:
CS2 + 3 Cl2 → CCl4 + S2Cl2 Disulfur dichloride can further chlorinate CS2 to CCl4:Carl R. Noller, Chlorinated and Fluorinated Aliphatic Hydrocarbons in Chemistry of Organic Compounds (1957), page 722
CS2 + 2 S2Cl2 → CCl4 + 6 S
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 this process named "chlorinolysis":
C2Cl6 + Cl2 → 2 CCl4
The production of carbon tetrachloride has steeply declined since the 1980s because of 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.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. In the 2010s, the total amount of CCl4 produced and imported into the US annually was under 70,000 tonnes.
Natural occurrence Carbon tetrachloride was discovered along with chloromethane and chloroform in oceans, marine algae and volcanoes. Natural emissions of carbon tetrachloride are insignificant compared to anthropogenic sources; for example, the Momotombo volcano in Nicaragua emits carbon tetrachloride at a flux of 82 grams per year while the global industrial emissions were at 2 × 1010 grams per year.
Carbon tetrachloride was found in red algae, specifically Asparagopsis taxiformis and Asparagopsis armata.Gribble, G. (2012). Progress in the Chemistry of Organic Natural Products. Austria: Springer Vienna. It was detected in Southern Californian ecosystems, salt lakes of the Kalmykian steppe and a common liverwort in the Czech Republic.Kinghorn, A. D., Falk, H., Gibbons, S., Asakawa, Y., Liu, J.-K., & Dirsch, V. M. (2023). Naturally occurring organohalogen compounds. Springer. p. 13
Safety At high temperatures in air, it decomposes or burns to produce poisonous phosgene. This was a common problem when carbon tetrachloride was used as a fire extinguisher and there have been deaths due to its conversion to phosgene.
Carbon tetrachloride is a suspected human carcinogen, although there is no sufficient evidence of carcinogenicity in humans. The World Health Organization reported repeated long-term exposure to carbon tetrachloride can induce hepatocellular carcinomas (hepatomas) in mice and rats. The doses inducing hepatic tumors in mice and rats are higher than those inducing cell toxicity. The International Agency for Research on Cancer (IARC) classified this compound in Group 2B, "possibly carcinogenic to humans".
Carbon tetrachloride is one of the most potent hepatotoxins (toxic to the liver), so much so that it is widely used in scientific research to evaluate hepatoprotective agents. Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system and degenerate the liver and kidneys, and prolonged exposure may lead to coma or death. Chronic exposure to carbon tetrachloride can cause liver and kidney damage.
Consumption of alcohol increases the toxic effects of carbon tetrachloride and may cause more severe organ damage, such as acute renal failure, in heavy drinkers. The doses that can cause mild toxicity to non-drinkers can be fatal to drinkers.Toxicological Profile for Carbon Tetrachloride. (2005). USA: Agency for Toxic Substances and Disease Registry.
The effects of carbon tetrachloride on human health and the environment have been assessed under REACH in 2012 in the context of the substance evaluation by France.
In 2008, a study of common cleaning products found the presence of carbon tetrachloride in "very high concentrations" (up to 101 mg/m3) 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 atmospheric concentration graphs in the gallery). CCl4 has an atmospheric lifetime of 85 years.The Atlas of Climate Change (2006) by Kirstin Dow and Thomas E. Downing
Uses
Prior to being phased out due to toxicity and environmental impact, carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in lava lamps. In the last case, carbon tetrachloride is a key ingredient that adds weight to the otherwise buoyant wax.
One speciality use of carbon tetrachloride was in stamp collecting, to reveal watermarks on postage stamps without damaging them. A small amount of the liquid is placed on the back of a stamp, sitting in a black glass or obsidian tray. The letters or design of the watermark can then be seen clearly. Today, this is done on lit tables without using carbon tetrachloride.
In organic chemistry, carbon tetrachloride serves as a source of chlorine in the Appel reaction.
Carbon tetrachloride made from heavy chlorine-37 has been used in the detection of neutrinos and antineutrinos. Raymond Davis Jr. used carbon tetrachloride in his experiments to detect antineutrinos. Cleaning Being a good solvent for many materials (such as grease and tar), carbon tetrachloride was widely used as a cleaning fluid for nearly 70 years. It is nonflammable and nonexplosive and did not leave any odour on the cleaned material, unlike gasoline, which was also used for cleaning at the time. It was used as a "safe" alternative to gasoline. It was first marketed as Katharin, in the early 1890sNeueste Erfindungen und Erfahrungen Auf Den Gebieten Der Praktischen Technik, Elektrotechnik, Der Gewerbe, Industrie, Chemie, Der Land und Hauswirthschaft. (1895). Austria: (n.p.). and as Benzinoform later.
Carbon tetrachloride was recommended for regularly cleaning the type slugs of typewriters in office settings in the 1940s.