Everything about Carbon Tetrachloride totally explained
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Carbon tetrachloride, also known by many other names (see Table) is the
chemical compound with the
formula CCl
4. 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. Colloquially, it's 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 720,000,000 kg.
Carbon tetrachloride was originally synthesised in 1839 by reaction of chloroform with chlorine, from the french chemist
Henri Victor Regnault, but now it's mainly synthesized from methane:
» CH4 + 4 Cl
2 → CCl
4 + 4
HCl
The production often utilizes by-products of other
chlorination reactions, such as the syntheses of
dichloromethane and
chloroform. Higher chlorocarbons are also subjected to "chlorinolysis:"
» C2Cl6 + Cl
2 → 2 CCl
4
Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of
carbon disulfide at 105 to 130 °C:
» CS
2 + 3
Cl2 → CCl
4 +
S2Cl2
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°.
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 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.
Carbon tetrachloride is one of the most potent hepatotoxins, and is widely used in scientific research to evaluate hepatoprotective agents 7,8
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 doesn't easily undergo free-radical reactions. Hence it's 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.
Solvent
It is used as a
solvent in synthetic chemistry research, but because of its adverse health effects, it's 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 doesn't 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. Use of carbon tetrachloride in determination of oil has been replaced by various other solvents.
Safety
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.
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).
Further Information
Get more info on 'Carbon Tetrachloride'.
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