Ĭarbon tetrachloride is also both ozone-depleting and a greenhouse gas. 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). 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. Chronic exposure to carbon tetrachloride can cause liver and kidney damage and could result in cancer. 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. 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.
The International Agency for Research on Cancer (IARC) classified this compound in Group 2B, " possibly carcinogenic to humans". The doses inducing hepatic tumours are higher than those inducing cell toxicity. The World Health Organization reports carbon tetrachloride can induce hepatocellular carcinomas (hepatomas) in mice and rats. Ĭarbon tetrachloride is a suspected human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals. This was a common problem when carbon tetrachloride was used as a fire extinguisher, there have been deaths due to its conversion to phosgene reported. Safety Īt high temperatures in air, it decomposes or burns to produce poisonous phosgene. In 1992, production in the U.S./Europe/Japan was estimated at 720,000 tonnes. 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. Higher chlorocarbons are also subjected to this process named "chlorinolysis": The production often utilizes by-products of other chlorination reactions, such as from the syntheses of dichloromethane and chloroform. Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 ☌: CS 2 + 3 Cl 2 → CCl 4 + S 2Cl 2īut now it is mainly produced from methane: Later in the 19th century, the name protochloride of carbon was used for tetrachloroethylene and carbon tetrachloride was called "bichloride of carbon". The protochloride of carbon has been previously misidentified as tetrachloroethylene due to being made with the same reaction of hexachloroethane. 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.Ĭarbon tetrachloride was originally synthesized by Michael Faraday who named it "protochloride of carbon" in 1820 via decomposition of hexachloroethane ("perchloride of carbon") which he synthesized by chlorination of ethylene. At −47.3 ☌ 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°. Solid tetrachloromethane has two polymorphs: crystalline II below −47.5 ☌ (225.6 K) and crystalline I above −47.5 ☌. It is volatile, giving off vapors with a smell characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene smell reminiscent of dry cleaners' shops. As a solvent, it is well suited to dissolving other non-polar compounds such as fats and oils. Methane gas has the same structure, making carbon tetrachloride a halomethane. Because of this symmetric geometry, CCl 4 is non-polar. 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. Tradenames include carbon tet, Thawpit and Benzinoform in the cleaning industry, Halon-104 in firefighting, Refrigerant-10 in HVACR, and Necatorina as a medication. Exposure to high concentrations of carbon tetrachloride can affect the central nervous system and degenerate the liver and kidneys. It was formerly widely used in fire extinguishers, as a precursor to refrigerants and as a cleaning agent, but has since been phased out because of environmental and safety concerns. It is a non-flammable, colourless liquid with a "sweet" chloroform-like smell that can be detected at low levels. Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also recognised by the IUPAC) is a chemical compound with the chemical formula CCl 4.
0 kommentar(er)
