Perchlorethylene

Tetrachloroethylene
IUPAC name
tetrachloroethene
other names
perchloroethene, perchloroethylene, perc, PCE
Identifiers
CAS number 127-18-4 Yes check.svgY
EC number 204-825-9
RTECS number KX3850000
SMILES
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
NFPA 704
NFPA 704.svg
0
2
0
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
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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

  • 1 Production
  • 2 Uses
    • 2.1 Historical applications
  • 3 Health and safety
    • 3.1 Testing for exposure
  • 4 References
  • 5 Further reading
  • 6 External links

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 used for the treatment for hookworm infestation.2

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.3 Like many chlorinated hydrocarbons, tetrachloroethene is a central nervous system depressant and can enter the body through respiratory or dermal exposure.4 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. Recent research has focused on the in place remediation of soil and ground water pollution by tetrachloroethylene. Instead of excavation or extraction for above-ground treatment or disposal, tetrachloroethylene contamination has been successfully remediated by chemical treatment or bioremediation. Bioremediation has been successful under anaerobic conditions by reductive dechlorination by Dehalococcoides sp. and under aerobic conditions by cometabolism by Pseudomonas sp. 56

Animal studies and a study of 99 twins by Dr. Samuel Goldman and researchers at the Parkinson's Institute in Sunnyvale, California determined there is a "lot of circumstantial evidence" that exposure to Tetrachloroethlene increases the risk of developing Parkinson's disease ninefold. Larger population studies are planned. 7

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.

References

  1. ^ 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
  2. ^ Young, M.D.; et al. (1960). "The Comparative Efficacy of Bephenium Hydroxynaphthoate and Tetrachloroethylene against Hookworm and other Parasites of Man". American Journal of Tropical Medicine and Hygiene 9 (5): 488-491. PMID 13787477. 
  3. ^ IARC monograph. "Tetrachloroethylene" Vol. 63, p. 159. Last Updated May 20, 1997. Last retrieved June 22, 2007.
  4. ^ Control of Exposure to Perchloroethylene in Commercial Drycleaning. Hazard Controls: Publication 97-157. National Institute for Occupational Safety and Health.
  5. ^ Ryoo, D., Shim, H., Arenghi, F. L. G., Barbieri, P., Wood T. K. (2001) Tetrachloroethylene, Trichloroethylene, and Chlorinated Phenols Induce Toluene-o-xylene Monooxoygenase Activity in Pseudomonas Stutzeri OX1, Applied Microbiol Biotechnol, 56: 545-549.
  6. ^ Deckard, L. A., Wills, J. C., Rivers, D. B. (1994) Evidence for aerobic degradation of tetrachloroethylene by bacterial isolate, Biotechnol. Lett., 16, 1221-1224.
  7. ^ Solvent Linked to Increased Risk of Parkinson's Disease

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: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.

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article http://en.wikipedia.org/wiki/Perchlorethylene. Additionally, in some cases elements from this article might be licensed under a different license. Please refer to the original article to check the license status http://en.wikipedia.org/wiki/Perchlorethylene.