Tetrachloroethylene
From Wikipedia, the free encyclopedia
| Tetrachloroethylene | |
|---|---|
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| IUPAC name |
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| Other names | perchloroethene, perchloroethylene, perc, PCE |
| Identifiers | |
| CAS number | [] |
| EC number | |
| RTECS number | KX3850000 |
| SMILES |
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| Properties | |
| Molecular formula | 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) |
| Solubility in water | 0.015 g/100 ml (20 °C) |
| Viscosity | 0.89 cP at 25 °C |
| Hazards | |
| MSDS | External MSDS |
| R-phrases | 40-51/53 |
| S-phrases | 23-36/37-61 |
| Flash point | Not flammable |
| Related compounds | |
| Related Related Haloforms | tetrabromoethylene tetraiodoethylene |
| Related compounds | trichloroethylene dichloroethene tetrachloroethane |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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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]
Contents |
[edit] 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.
[edit] 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.
[edit] 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.
[edit] 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. 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.
[edit] 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.
[edit] 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.
[edit] Further reading
- "Toxicological Profile for Tetrachloroethene". Agency for Toxic Substances and Disease Registry. 1997. http://www.atsdr.cdc.gov/toxprofiles/tp18.html.
- 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:.
[edit] 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.
