Carbon tetrachloride

Carbon tetrachloride
General
Systematic name	Carbon tetrachloride Tetrachloromethane
Other names	benziform, carbon chloride, methane tetrachloride, perchloromethane tetrachoromethane
Molecular formula	CCl4
SMILES	ClC(Cl)(Cl)Cl
Molar mass	153.82 g/mol
Appearance	colorless liquid
CAS number	[56-23-5]
Properties
Density and phase	1.5842 g/ml, liquid
Solubility in water	0.08 g/100 ml (20 °C)
Melting point	−22.9 °C (250 K)
Boiling point	76.8 °C (350 K)
Viscosity	0.901 cP at 25 °C
Structure
Molecular shape	tetrahedral
Dipole moment	zero
Thermodynamic data
Std enthalpy change of formation ΔfHoliquid	−128 kJ/mol
Standard molar entropy Sogas	216.4 J.K−1.mol−1
Hazards
MSDS	External MSDS
EU classification	Toxic (T) Carc. Cat. 3 Dangerous for the environment (N)
NFPA 704	NFPA 704 safety square 3
R-phrases	Template:R23/24/25, Template:R40, Template:R48/23, Template:R59, Template:R52/53
S-phrases	Template:S1/2, Template:S23, Template:S36/37, Template:S45, Template:S59, Template:S61
Flash point	non flammable
RTECS number	FG4900000
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related carbon tetrahalides	Tetrafluoromethane Tetrabromomethane Tetraiodomethane
Related chloromethanes	Chloromethane Dichloromethane Chloroform
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Carbon tetrachloride, also known by other names (see Table) is the chemical compound CCl₄. It is widely used in synthetic chemistry and formerly widely used in fire extinguishers and refrigeration, but largely abandoned. At room temperature and pressure, 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". Trade names include Benzinoform, Freon 10, Halon 104, Tetraform, and Tetrasol.

Production

Most carbon tetrachloride is produced by the chlorination of carbon disulfide at 105 to 130 °C:

CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂

CCl₄ is also a byproduct in the synthesis of dichloromethane and chloroform via the reaction:

CH₄ + 4Cl₂ → CCl₄ + 4HCl

Chemical 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 having no net dipole moment, i.e. CCl₄ is non-polar.

As a solvent, it is well suited to dissolving other non-polar compounds. 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.

Carbon tetrachloride has practically no flammability at lower temperatures.

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.

Uses

In the early 20th century, carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in fire extinguishers. However, once it became apparent that carbon tetrachloride exposure had severe adverse health effects, safer alternatives 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 and R-12. However, these refrigerants are now believed to play a role in ozone depletion and have been phased out of use, though it is still used to manufacture less destructive refrigerants.

Carbon tetrachloride has also been used in the detection of neutrinos, and is a useful source of chlorine in the Appel reaction.

It is sometimes useful as solvent for infrared spectroscopy because there are no significant absorption bands > 1600 cm^-1. Because carbon tetrachloride does not have any hydrogens, 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 allow for deuterium lock by the spectrometer.

Safety

Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system and may result (after prolonged exposure) to coma and even death can occur. Chronic exposure to carbon tetrachloride can cause liver and kidney damage and may result in cancer. More information can be found in an MSDS.

Carbon tetrachloride is also an ozone-depleting greenhouse gas, but is rarely mentioned when talking about ozone depletion, due to the fact that its levels have been steadily decreasing since 1996.

See also

• Appel reaction
• Dutch standards

References

1. 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.{{cite journal}}: CS1 maint: multiple names: authors list (link)
2. 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. {{cite journal}}: Cite journal requires |journal= (help)

External links

• International Chemical Safety Card 0024
• NIOSH Pocket Guide to Chemical Hazards
• IARC Monograph: "Carbon Tetrachloride"
• Carbon tetrachloride MSDS at Hazardous Chemical Database