Carbon tetrachloride

Description

Carbon tetrachloride is a manufactured chemical and does not occur naturally in the environment. It is produced by chlorination of a variety of low molecular weight hydrocarbons such as carbon disulfide, methane, ethane, propane, or ethylene dichloride and also by thermal chlorination of methyl chloride. Carbon tetrachloride is a precursor for chlorofluorocarbon (CFC) gases that have been used as aerosol propellant. A decrease in this use is occurring due to the agreement reached in the Montreal Protocol for the reduction of environmental concentrations of ozone-depleting chemicals, including carbon tetrachloride.

Description

Readers of a certain age can remember when “carbon tet” was the go-to household solvent that easily removed organic residues such as adhesives and oils from almost any surface. It was also a widely used dry-cleaning solvent, refrigerant, and fire suppressant.
During the 1970s and ’80s, however, toxicologists discovered that inhalation of or skin contact with carbon tetrachloride (CCl4) can damage many organs, including the liver, kidneys, and central nervous system (see hazard table). CCl4 is also a “greenhouse gas” that, according to the 1995 Montreal Protocol, depletes ozone in the Earth’s stratosphere. Consequently, production and use have been significantly reduced.
In its heyday, CCl4 was produced by chlorinating C1 compounds such as chloroform, carbon disulfide, and, in later years, methane. What little is available today is a coproduct from the manufacture of chloroform and dichloromethane; however, US production is still 15 times the amount called for in the Montreal Protocol.
The CCl4 currently produced is used as a feedstock for ozone-safe refrigerants and in some minor agricultural and industrial processes. In a recent draft risk assessment of CCl4 standards under the Toxic Substances Control Act, the US Environmental Protection Agency reports that the compound is safe to use in manufacturing plants if workers wear appropriate personal protective equipment. The assessment is scheduled to be finalized by June.

Description

Due to its symmetrical structure, carbon tetrachloride (CCl4) is non-polar. Its non-polar nature makes it a suitable solvent for dissolving non-polar compounds. Carbon tetrachloride is convenient as a solvent for NMR because it contains no protons, however, its poor dissolving power limits its usefulness.

Chemical properties

Carbon tetrachloride, CC14, also known as tetrachloromethane, perchloro methane, and benzinoform, is a colorless liquid with a boiling point of 77 °C (170 OF). It is used as a solvent for lacquers, resin, and rubbers,and as a dry cleaning agent.

Chemical properties

Carbon tetrachloride readily dissolves stannic chloride, SnCl4, but not ferric chloride, FeCl3. Carbon tetrachloride forms a large number of binary and several ternary azeotropic mixtures; a partial list of the former is shown in Table 2. Many polymer films, eg, polyethylene and polyacrylonitrile, are permeable to carbon tetrachloride vapor. Carbon tetrachloride vapor affects the explosion limits of several gaseous mixtures, eg, air-hydrogen and airmethane. The extinctive effect that carbon tetrachloride has on a flame, mainly because of its cooling action, is derived from its high thermal capacity.
As chlorination proceeds from methyl chloride to carbon tetrachloride, the length of the C?Cl bond is decreased from 0.1786 nm in the former to 0.1755 nm in the latter. At ca 400 °C (752 °F), thermal decomposition of carbon tetrachloride occurs very slowly, whereas at 900–1,300 °C (1,652–2,372 °F) dissociation is extensive, forming perchloroethylene and hexachloroethane and liberating some chlorine. Subjecting the vapor to an electric arc also forms perchloroethylene and hexachloroethane, as well as hexachlorobenzene, elementary carbon, and chlorine.

Physical properties

Carbon tetrachloride is a volatile colourless clear heavy liquid with a characteristic sweet non-irritant odour. The odour threshold in water is 0.52 mg/litre and in air is > 10 ppm. Carbon tetrachloride is miscible with most aliphatic solvents and it is a solvent for benzyl resins, bitumen, chlorinated rubber, rubber-based gums, oils and fats.The solubility in water is low. Carbon tetrachloride is non-flammable and is stable in the presence of air and light. Decomposition may produce phosgene, carbon dioxide and hydrochloric acid.

History

In the 1890s, commercial manufacturing processes were being investigated by the United Alkali Co. in England. At the same time it was also produced in Germany, exported to the United States, and retailed as a spotting agent under the trade name Carbona. Large-scale production of carbon tetrachloride in the United States commenced in the early 1900s. By 1914, annual production fell just short of 4500 metric tons and was used primarily for dry cleaning and for charging fire extinguishers. During World War I, U.S. production of carbon tetrachloride expanded greatly; its use was extended to grain fumigation and the rubber industry. In 1934 it was supplanted as the predominant dry-cleaning agent in the United States by perchloroethylene, which is much less toxic and more stable. During the years immediately preceding World War II, trichloroethylene began to displace carbon tetrachloride from its then extensive market in the United States as a metal degreasing solvent. Carbon tetrachloride is more difficult to recover from degreasing operations, more readily hydrolyzed, and more toxic than trichloroethylene C2HCl3. The demands of World War II stimulated production and marked the beginning of its use as the starting material for chlorofluoromethanes, by far the most important application for carbon tetrachloride.

The Uses of Carbon tetrachloride

Carbon tetrachloride is used as a solvent, infire extinguishers, in dry cleaning, and in themanufacture of fluorocarbon propellents.As solvent for oils, fats, lacquers, varnishes, rubber waxes, resins; starting material in manufacture of organic Compounds. Pharmaceutic aid (solvent).

The Uses of Carbon tetrachloride

A mixture of the SM (100 g, 497 mmol), NBS (88.5 g, 497 mmol), and AIBN (10 g, 50 mmol) in CCl4 (700 mL) was stirred at reflux for 12 h. The mixture was cooled to RT, diluted with H2O, and extracted with EtOAc. The org layer was separated, dried (Na2SO4), and concentrated. The residue was purified by silica gel flash chromatography to provide the product. [48 g, 42%]

The Uses of Carbon tetrachloride

Decades ago, this compound was mixed with ether and sold as Carbona, a dry-cleaning fluid for clothes. It is no longer permissible to sell or buy CCL4 for household use. It is classed as a carcinogen by the U.S. government and is toxic if ingested, inhaled, or absorbed by the skin. Carbon tetrachloride is used to manufacture CFHCs, to fumigate grains to kill insects, and in the production of semiconductors.

The Uses of Carbon tetrachloride

In the manufacture of chlorofluorocarbons, which in turn are primarily used as refrigerants; formerly used widely as a solvent, also as a grain fumigant and in fire extinguishers. Because of toxicity consumer uses have been discontinued and only industrial use remains.

Definition

ChEBI: A chlorocarbon that is methane in which all the hydrogens have been replaced by chloro groups.

Production Methods

Carbon tetrachloride is made by the reaction of carbon disulfide and chlorine in the presence of a catalyst, such as iron or antimony pentachloride:
CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂
Sulfur chloride is removed by treatment with caustic soda solution. The product is purified by distillation.
Alternatively, CCl4 may be prepared by heating a mixture of chlorine and methane at 250 to 400°C.
CH₄ + 4Cl2 → CCl₄ + 4HCl

General Description

Carbon tetrachloride appears as a clear colorless liquid with a characteristic odor. Denser than water (13.2 lb / gal) and insoluble in water. Noncombustible. May cause illness by inhalation, skin absorption and/or ingestion. Used as a solvent, in the manufacture of other chemicals, as an agricultural fumigant, and for many other uses.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

Carbon tetrachloride is a commonly used liquid in fire extinguishers to combat small fires. Carbon tetrachloride has no flash point, Carbon tetrachloride is not flammable. However, when heated to decomposition, Carbon tetrachloride will emit fumes of extremely toxic phosgene and of hydrogen chloride. Forms explosive mixtures with chlorine trifluoride, calcium hypochlorite, decaborane, dinitrogen tetraoxide, fluorine. Forms impact-sensitive explosive mixtures with particles of many metals: lithium, sodium, potassium, beryllium, zinc, aluminum, barium. Vigorous exothermic reaction with allyl alcohol, boron trifluoride, diborane, disilane, aluminum chloride, dibenzoyl peroxide, potassium tert-butoxide, liquid oxygen, zirconium. [Bretherick, 5th ed., 1995, p. 666]. Potentially dangerous reaction with dimethylformamide or dimethylacetamide in presence of iron [Cardillo, P. et al., Ann. Chim. (Rome), 1984, 74, p. 129].

Hazard

Carbon tetrachloride is a poison and also a carcinogen. The acute toxicity of this compound in humans is of low order. However, the ingestion of the liquid can be fatal, death resulting from acute liver or kidney necrosis. (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed. New York: John Wiley & Sons.) The acute poisoning effects are headache, dizziness, fatigue, stupor, nausea, vomiting, diarrhea, and liver damage. Chronic exposure can damage both liver and kidney. Carbon tetrachloride also is a suspected human carcinogen. It causes liver and thyroid cancers in experimental animals.

Health Hazard

Carbon tetrachloride exhibits low acute tox icity by all routes of exposure. The acute poisoning effects include dizziness, fatigue,headache, nervousness, stupor, nausea, vom iting, diarrhea, renal damage, and liverinjury. The dosages that produce toxic act ions in animals vary with the species. Theoral LD50 values in rats, rabbits, and mice are2800, 5760, and 8263 mg/kg, respectively(NIOSH 1986).
Ingestion of carbon tetrachloride can befatal to humans, death resulting from acuteliver or kidney necrosis. Chronic exposuremay cause liver and kidney damage. Expo sure to a 10-ppm concentration for severalweeks produced accumulation of fat in the liv ers of experimental animals (ACGIH 1986).Substances such as ethanol and barbituratescause potentiation of toxicity of carbon tetra chloride. Skin contact can cause dermatitis.
Azri and coworkers (1990) have investi gated carbon tetrachloride–induced hepato toxicity in rat liver slices. Liver slices frommale rats were incubated and exposed tocarbon tetrachloride vapors, and the degreeof injury to cellular tissue was determined.Covalent binding of CCl4 radical to proteinsand lipid molecules in a slice caused the cel lular injury. The toxicity depended on thevapor concentration and the time of expo sure. Azri and coworkers reported furtherthat rats pretreated with phenobarbital weremore rapidly intoxicated even at a lower con centration of carbon tetrachloride vapors. Onthe other hand, pretreatment with allyliso propylacetamide inhibited the toxicity of car bon tetrachloride.
Carbon tetrachloride is a suspected humancarcinogen. Oral and subcutaneous adminis tration of this compound in rats caused liverand thyroid cancers in the animals.

Flammability and Explosibility

Carbon tetrachloride is noncombustible. Exposure to fire or high temperatures may lead to formation of phosgene, a highly toxic gas.

Industrial uses

Carbon tetrachloride is a clear, heavy liquid with a strong, aromatic odor. Its formula is CC14. It is produced in large quantities for use in the manufacturing of refrigerants and propellants for aerosol cans. It is also used as a feedstock in the synthesis of chlorofluorocarbons and other chemicals, in petroleum refining, pharmaceutical manufacturing, and general solvent use. Until the mid- 1960s, it was also widely used as a cleaning fluid, both in industry, where it served as a degreasing agent, and in the home, where it was used as a spot remover and in fire extinguishers.
Carbon tetrachloride is a highly volatile liquid with a strong etherial odor similar to chloroform. It mixes sparingly with water and is not flammable. When heated to decomposition, it emits highly toxic fumes of phosgene and hydrogen chloride. There is strong evidence that the toxicity of carbon tetrachloride is dramatically increased by its interaction with alcohols, ketones, and a range of other chemicals.
Carbon tetrachloride is known to deplete the ozone layer, where it is responsible for 17% of the ozone-destroying chlorine now in the stratosphere due to human activities. Carbon tetrachloride has a half-life of between 30 and 100 years.Its DOT Label is Poison, and its UN number is 1846.

Safety Profile

Also forms explosive mixtures with chlorine trifluoride, calcium hypochlorite (heatsensitive), calcium dtsllicide (frictionand pressuresensitive), triethyldialuminum trichloride (heatsensitive), decaborane(l4) (impact-sensitive), dinitrogen tetraoxide. Violent or explosive reaction on contact with fluorine. Forms explosive mixtures with ethylene between 25' and 105' and between 30 and 80 bar. Potentially explosive reaction on contact with boranes. 9:l mixtures of methanol and cCl4 react exothermically with aluminum, magnesium, or zinc. Potentially dangerous reaction with dimethyl formamide, 1,2,3,4,5,6 hexachlorocyclohexane, or dtmethylacetamide when iron is present as a catalyst. CCh has caused explosions when used as a fire extingusher on wax and uranium fires. Incompatible with aluminum trichloride, dtbenzoyl peroxide, potassiumtert-butoxide. Vigorous exothermic reaction with allyl alcohol, Al(C2H5)3, (benzoyl peroxide + C2H4), BrF3, diborane, dsilane, liquid O2, Pu, (AgClO4 + HCl), potassiumtert-butoxide, tetraethylenepentamine, tetrasilane, trisilane, Zr. When heated to decomposition it emits toxic fumes of Cl and phosgene. It has been banned from household use by the FDA.

Potential Exposure

Carbon tetrachloride, and organochlorine, is used as a solvent for oils, fats, lacquers, varnishes, rubber, waxes, and resins. Fluorocarbons are chemically synthesized from it. It is also used as an azeotropic drying agent for spark plugs; a dry-cleaning agent; a fire extinguishing agent; a fumigant, and an anthelmintic agent. The use of this solvent is widespread, and substitution of less toxic solvents when technically possible is recommended.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit

Carcinogenicity

Carbon tetrachloride is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals.

Source

Carbon tetrachloride is used in fumigant mixtures such as 1,2-dichloroethane (Granosan) because it reduces the fire hazard (Worthing and Hance, 1991).

Environmental Fate

Biological. Carbon tetrachloride was degraded by denitrifying bacteria forming chloroform (Smith and Dragun, 1984). An anaerobic species of Clostridium biodegraded carbon tetrachloride by reductive dechlorination yielding trichloromethane, dichloromethane and unidentified products (G?lli and McCarty, 1989). Chloroform also formed by microbial degradation of carbon tetrachloride using denitrifying bacteria (Smith and Dragun, 1984).
Carbon tetrachloride (5 and 10 mg/L) showed significant degradation with rapid adaptation in a static-culture flask-screening test (settled domestic wastewater inoculum) conducted at 25°C. Complete degradation was observed after 14 days of incubation (Tabak et al., 1981).
Chemical/Physical. Under laboratory conditions, carbon tetrachloride partially hydrolyzed to chloroform and carbon dioxide (Smith and Dragun, 1984). Complete hydrolysis yielded carbon dioxide and hydrochloric acid (Kollig, 1993). Carbon tetrachloride slowly reacts with hydrogen sulfide in aqueous solution yielding carbon dioxide via the intermediate carbon disulfide. However, in the presence of two micaceous minerals (biotite and vermiculite) and amorphous silica, the rate of transformation increased. At 25°C and a hydrogen sulfide concentration of 1 mM, the half-lives for carbon tetrachloride were calculated to be 2,600, 160 and 50 days for the silica, vermiculite and biotite studies, respectively. In all three studies, the major transformation pathway is the formation of carbon disulfide which undergoes hydrolysis yielding carbon dioxide (81–86% yield) and hydrogen sulfide ions. Minor intermediates detected include chloroform (5–15% yield),carbon monoxide (1–2% yield) and a nonvolatile compound tentatively identified as formic acid (3–6% yield) (Kriegman-King and Reinhard, 1992).
Anticipated products from the reaction of carbon tetrachloride with ozone or hydroxyl radicals in the atmosphere are phosgene and chloride radicals (Cupitt, 1980). Phosgene is hydrolyzed readily to hydrochloric acid and carbon dioxide (Morrison and Boyd, 1971).
Matheson and Tratnyek (1994) studied the reaction of fine-grained iron metal in an anaerobic aqueous solution (15°C) containing carbon tetrachloride (151 μM). Initially, carbon tetrachloride underwent rapid dehydrochlorination forming chloroform, which further degraded to methylene chloride and chloride ions. The rate of reaction decreased with each dehydrochlorination step. However, after 1 hour of mixing, the concentration of carbon tetrachloride decreased from 151 to approximately 15 μM. No additional products were identified although the authors concluded that environmental circumstances may exist where degradation of methylene chloride may occur. They also reported that reductive dehalogenation of carbon tetrachloride and other chlorinated hydrocarbons used in this study appears to take place in conjunction with the oxidative dissolution or corrosion of the iron metal through a diffusion-limited surface reaction.
The evaporation half-life of carbon tetrachloride (1 mg/L) from water at 25°C using a shallow-pitch propeller stirrer at 200 rpm at an average depth of 6.5 cm is 29 minutes (Dilling, 1977).

storage

Carbon tetrachloride should be handled in the laboratory using the "basic prudent practices".

Shipping

UN1846 Carbon tetrachloride, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Purification Methods

For many purposes, careful fractional distillation gives adequate purification. Carbon disulfide, if present, can be removed by shaking vigorously for several hours with saturated KOH, separating, and washing with water: this treatment is repeated. The CCl4 is shaken with conc H2SO4 until there is no further coloration, then washed with water, dried with CaCl2 or MgSO4 and distilled (from P2O5 if desired). It must not be dried with sodium. An initial refluxing with mercury for 2hours removes sulfides. Other purification steps include passage of dry CCl4 through activated alumina, and distillation from KMnO4. Carbonyl containing impurities can be removed by percolation through a Celite column impregnated with 2,4-dinitrophenylhydrazine (DNPH), H3PO4 and water. (Prepared by dissolving 0.5g DNPH in 6mL of 85% H3PO4 by grinding together, then mixing with 4mL of distilled water and 10g Celite.) [Schwartz & Parks Anal Chem 33 1396 1961]. Photochlorination of CCl4 has also been used: CCl4 to which a small amount of chlorine has been added is illuminated in a glass bottle (e.g. for 24hours with a 200W tungsten lamp near it), and, after washing out the excess chlorine with 0.02M Na2SO3, the CCl4 is washed with distilled water and distilled from P2O5. It can be dried by passing through 4A molecular sieves and distilled. Another purification procedure is to wash CCl4 with aqueous NaOH, then repeatedly with water and N2 gas is bubbled through the liquid for several hours. After drying over CaCl2 it is percolated through silica gel and distilled under dry N2 before use [Klassen & Ross J Phys Chem 91 3664 1987]. [Beilstein 1 IV 56.]

Toxicity evaluation

Most of the carbon tetrachloride produced is released to the atmosphere. In the atmosphere, photodegradation by shorter wavelength ultraviolet radiation appears to be the primary removal process although it is very stable in the environment remaining in the air for several years before breaking down, so a significant global transport is expected. The estimated half-life of atmospheric carbon tetrachloride is 30–100 years. Small amounts can be released to the water but due to the relatively high rate of volatilization from water, carbon tetrachloride tends to evaporate in a short time. It is stable to hydrolysis in water. Most of the amount released to soil evaporates rapidly due to its high vapor pressure but a small proportion could remain associated to the soil organic matter. Carbon tetrachloride is mobile in most soils depending on the organic carbon content and can reach groundwater where it remains for long periods before it is broken down to other chemicals.

Incompatibilities

Oxidative decomposition on contact with hot surfaces, flames, or welding arcs. Carbon tetrachloride decomposes forming toxic phosgene fumes and hydrogen chloride. Decomposes violently (producing heat) on contact with chemically active metals, such as aluminum, barium, magnesium, potassium, sodium, fluorine gas, allyl alcohol, and other substances, causing fire and explosion hazard. Attacks copper, lead, and zinc. Attacks some coatings, plastics, and rubber. Becomes corrosive when in contact with water; corrosive to metals in the presence of moisture.

Waste Disposal

Incineration, preferably after mixing with another combustible fuel; care must be exercised to assure complete combustion to prevent the formation of phosgene; an acid scrubber is necessary to remove the halo acids produced. Recover and purify by distillation where possible.