Tetrachloroethylene
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| Names | |||
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| IUPAC name
tetrachloroethene
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| Other names
perchloroethene, perchloroethylene, perc, PCE
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| Identifiers | |||
3D model (JSmol)
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| ECHA InfoCard | 100.004.388 | ||
| EC Number |
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| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |||
| C2Cl4 | |||
| Molar mass | 165.8 g/mol | ||
| Appearance | Clear, colorless liquid | ||
| Density | 1.622 g/cm3, liquid | ||
| Melting point | −19 °C (254 K) | ||
| Boiling point | 121.1 °C (394 K) | ||
| 0.015 g/100 ml (20 °C) | |||
| Viscosity | 0.89 cP at 25 °C | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
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Harmful (Xn), Dangerous for the environment (N) | ||
| Flash point | Not flammable | ||
| Related compounds | |||
| Supplementary data page | |||
| Tetrachloroethylene (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Tetrachloroethylene, also known under its systematic name tetrachloroethene and many other names, is a chlorocarbon with the formula Cl2C=CCl2. It is a colourless liquid widely used for dry cleaning of fabrics, hence it is sometimes called "dry-cleaning fluid." It has a sweet odor detectable by most people at a concentration of 1 part per million (1 ppm). Worldwide production was about 1 megaton in 1985.[1]
Production
Michael Faraday first synthesized tetrachloroethene in 1821 by thermal decomposition of hexachloroethane.
- C2Cl6 → C2Cl4 + Cl2
Most tetrachloroethene is produced by high temperature chlorinolysis of light hydrocarbons. The method is related to Faraday's discovery since hexachloroethane is generated and thermally decomposes.[1] Side products include carbon tetrachloride, hydrogen chloride, and hexachlorobutadiene.
Several other methods have been developed. When 1,2-dichloroethane is heated to 400 °C with chlorine, tetrachloroethene is produced by the chemical reaction:
- ClCH2CH2Cl + 3 Cl2 → Cl2C=CCl2 + 4 HCl
This reaction can be catalyzed by a mixture of potassium chloride and aluminium chloride or by activated carbon. Trichloroethylene is a major byproduct, which is separated by distillation.
Uses
Tetrachloroethylene is an excellent solvent for organic materials. Otherwise it is volatile, highly stable, and nonflammable. For these reasons, it is widely used in dry cleaning. Usually as a mixture with other chlorocarbons, it is also used to degrease metal parts in the automotive and other metalworking industries. It appears in a few consumer products including paint strippers and spot removers.
Historical applications
Tetrachloroethene was once extensively used as an intermediate in the manufacture of HFC-134a and related refrigerants. In the early 20th century, tetrachloroethene was the most effective available treatment for hookworm.
Health and safety
The International Agency for Research on Cancer has classified tetrachloroethene as a Group 2A carcinogen, which means that it is probably carcinogenic to humans.[2] Like many chlorinated hydrocarbons, tetrachloroethene is a central nervous system depressant and can enter the body through respiratory or dermal exposure.[3] Tetrachloroethene dissolve fats from the skin, potentially resulting in skin irritation.
Tetrachloroethene is a common soil contaminant. Because of the mobility of PCE in groundwater, its toxicity at low levels, and its density (which causes it to sink below the water table), cleanup activities are more difficult than for oil spills.
Testing for exposure
Tetrachloroethene exposure can be evaluated by a breath test, analogous to breath-alcohol measurements. Because it is stored in the body's fat and slowly released into the bloodstream, tetrachloroethene can be detected in the breath for weeks following a heavy exposure. Tetrachloroethylene and trichloroacetic acid (TCA), a breakdown product of tetrachloroethene, can be detected in the blood.
Popular culture
- Tetrachloroethene contamination was used as a plot focus in a story arc of the TV show Ghostwriter.
- It has been featured in the episode Foothold (season 3) of Stargate SG1 where one of the side effects was hallucinations and paranoia.
- The health risks of tetrachloroethene and trichloroethene are discussed in A Civil Action, which involves a Woburn, Massachusetts, lawsuit where a cluster of leukemia developed, arguably due to high perc levels.
References
- ^ a b M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06 233.pub2
- ^ IARC monograph. "Tetrachloroethylene" Vol. 63, p. 159. Last Updated May 20, 1997. Last retrieved June 22, 2007.
- ^ [http://www.cdc.gov/niosh/hc19.html Control of Exposure to Perchloroethylene in Commercial Drycleaning]. Hazard Controls: Publication 97-157. National Institute for Occupational Safety and Health.
Further reading
- "Toxicological Profile for Tetrachloroethene". Agency for Toxic Substances and Disease Registry. 1997.
- 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". Journal of Environmental Forensics. 1: 69–81. doi:10.1006/enfo.2000.0010.
External links
- ATSDR Case Studies in Environmental Medicine: Tetrachloroethylene Toxicity U.S. Department of Health and Human Services
- Australian National Pollutant Inventory (NPI) page
- "Toxic Fumes May Have Made Gunman Snap", by Julian Kesner, New York Daily News, April 20, 2007.