Tetrachloroethylene: Difference between revisions

| verifiedrevid = 418144966

| Name = Tetrachloroethylene

| ImageFileL1 = Tetrachloroethylene.svg

| ImageSizeL1 = 100px

| ImageNameL1 = Tetrachloroethylene

| ImageFileR1 = Tetrachloroethylene-3D-vdW.png

| ImageSizeR1 = 120px

| ImageNameR1 = Tetrachloroethylene

| IUPACName = Tetrachloroethene

| OtherNames = Perchloroethene; Perchloroethylene; Perc; PCE

| Section1 = {{Chembox Identifiers

| SMILES = Cl/C(Cl)=C(/Cl)Cl

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 114062

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 127-18-4

| EINECS = 204-825-9

| RTECS = KX3850000

| UNNumber = 1897

| KEGG_Ref = {{keggcite|correct|kegg}}

| KEGG = C06789

| Section2 = {{Chembox Properties

| C=2|Cl=4

| Appearance = Clear, colorless liquid

| Density = 1.622 g/cm³

| Solubility = 0.015 g/100 mL (20 °C)

| MeltingPtC = -19

| BoilingPtC = 121.1

| Viscosity = 0.89 [[Poise|cP]] at 25 °C

| Section7 = {{Chembox Hazards

| NFPA-F = 0 | NFPA-H = 2 | NFPA-R = 0 | NFPA-O =

| ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/t0767.htm External MSDS]

| MainHazards = Harmful (Xn),<br />Dangerous for<br /> the environment (N)

| FlashPt = Not flammable

| RPhrases = {{R40}} {{R51/53}}

| SPhrases = {{S23}} {{S36/37}} {{S61}}

| Section8 = {{Chembox Related

| Function = Related [[organohalide]]s

| OtherFunctn = [[Tetrabromoethylene]]<br />[[Tetraiodoethylene]]

| OtherCpds = [[Trichloroethylene]]<br />[[Dichloroethene]]<br />[[Tetrachloroethane]]

'''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 megatonne in 1985.<ref name=Ullmann>M. Rossberg et al. “Chlorinated Hydrocarbons” in ''Ullmann’s Encyclopedia of Industrial Chemistry'', 2006, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a06 233.pub2}}</ref>

==Production==

[[Michael Faraday]] first synthesized tetrachloroethene in 1821 by thermal decomposition of [[hexachloroethane]].

:C₂Cl₆ &rarr; 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.<ref name=Ullmann/> 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 [[hydrogen chloride|HCl]]

According to an EPA report of 1976, the quantity of Tetrachloroethylene (also known as perchloroethylene or PCE) produced in the United States in just one year 1973, totaled 706 million pounds (320,000 metric tons). Daimond Shamrock, Dow Chemical Compnay, E.I DuPont and Vulcan Materials Company (Chemical Division) were among the top eight producers nationwide. <ref>"Assessment of Hazardous Waste Practices: Organic Chemicals, Pesticides and Explosives Industries" prebpublication issue for EPA Libraries and Solid Waste Management Agencies under contract # 68-01-2919, USEPA 1976 </ref>

Tetrachloroethylene is an excellent [[solvent]] for [[organic chemistry|organic]] materials. Otherwise it is volatile, highly stable, and [[flammable|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 [[automobile|automotive]] and other metalworking industries. It appears in a few consumer products including [[paint stripper]]s and spot removers.

Tetrachloroethene was once extensively used as an intermediate in the manufacture of [[1,1,1,2-Tetrafluoroethane|HFC-134a]] and related [[refrigerant]]s. In the early 20th century, tetrachloroethene was used for the treatment for [[hookworm]] infestation.<ref>{{cite journal |last=Young |first=M.D. |authorlink= |coauthors=''et al.'' |year=1960 |month= |title=The Comparative Efficacy of Bephenium Hydroxynaphthoate and Tetrachloroethylene against Hookworm and other Parasites of Man |journal=American Journal of Tropical Medicine and Hygiene |volume=9 |issue=5 |pages=488–491 |pmid=13787477 |url= |accessdate= |quote= }}</ref>

The [[International Agency for Research on Cancer]] has classified tetrachloroethene as a Group 2A [[carcinogen]], which means that it is probably carcinogenic to humans.<ref>IARC monograph. [http://www.inchem.org/documents/iarc/vol63/tetrachloroethylene.html Tetrachloroethylene], Vol. 63, p. 159. Last Updated May 20, 1997. Last retrieved June 22, 2007.</ref> Like many [[Organochlorine compound|chlorinated hydrocarbons]], tetrachloroethene is a [[central nervous system]] depressant and can enter the body through respiratory or dermal exposure.<ref>[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.</ref> Tetrachloroethene dissolves fats from the skin, potentially resulting in skin irritation.

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.<ref>[http://www.michaeljfox.org/newsEvents_parkinsonsInTheNews_article.cfm?ID=605 Industrial Solvent Linked to Increased Risk of Parkinson's Disease]</ref>

===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]].

In Europe, the Scientific Committee on Occupational Exposure Limits ([[SCOEL]]) recommends for tetrachloroethylene an [[occupational exposure limit]] (8h time-weighted average) of 20 ppm and a short-term exposure limit (15 min) of 40 ppm.<ref>{{cite web|url= http://ec.europa.eu/social/keyDocuments.jsp?type=0&policyArea=82&subCategory=153&country=0&year=0&advSearchKey=recommendation&mode=advancedSubmit&langId=en|title=SCOEL recommendations|date=2011-04-22|accessdate=2011-04-22}}</ref>

== Environmental contamination ==

Tetrachloroethene is a common [[soil contaminant]]. With a specific gravity greater than 1, tetrachloroethylene will be present as a [[dense nonaqueous phase liquid]] if sufficient quantities of liquid are spilled in the environment. Because of its mobility 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 [[environmental remediation|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.<ref>{{cite journal | doi = 10.1007/s002530100675 | author = Ryoo, D., Shim, H., Arenghi, F. L. G., Barbieri, P., Wood T. K. | year = 2001 | title = Tetrachloroethylene, Trichloroethylene, and Chlorinated Phenols Induce Toluene-o-xylene Monooxoygenase Activity in Pseudomonas Stutzeri OX1 | journal = Applied Microbiol Biotechnol | volume = 56 | pages = 545–549}}</ref><ref>{{cite journal | doi = 10.1007/BF01020855 | author = Deckard, L. A., Wills, J. C., Rivers, D. B. | year = 1994 | title = Evidence for aerobic degradation of tetrachloroethylene by bacterial isolate | journal = Biotechnol. Lett. | volume = 16 | pages = 1221–1224}}</ref> Partial degradation daughter products include [[trichloroethylene]], cis-[[1,2-dichloroethene]] and [[vinyl chloride]]; full degradation converts tetrachloroethylene to ethene and chloride dissolved in water.

It has been estimated that about 85% of tetrachloroethylene is released into the [[atmosphere]]; [[OECD]] models assumed 90% release into the air and 10% to water. Based on these models, its distribution in the environment is estimated to be in the air (76.39% - 99.69%), water (0.23% - 23.2%), soil (0.06-7%), with the remainder in the sediment and biota. Estimates of lifetime in the atmosphere vary, but a 1987 survey estimated the lifetime in the air has been estimated at about 2 months in the Southern Hemisphere and 5–6 months in the Northern Hemisphere. Degradation products observed in a laboratory include phosgene, trichloroacetyl chloride, hydrogen chloride, carbon dioxide, and carbon monoxide. In water, tetrachloroethylene is degraded very slowly by [[hydrolysis]], and it is persistent under [[aerobic]] conditions. It is degraded through reductive dechlorination under anaerobic conditions, with the degradation products including trichloroethene, dichloroethene, vinyl chloride, ethene, and ethane.<ref>Watts P. (2006). [http://www.who.int/ipcs/publications/cicad/cicad68.pdf Concise International Chemical Assessment Document 68: TETRACHLOROETHENE], [[World Health Organization]]</ref>

* {{cite web | publisher = [[Agency for Toxic Substances and Disease Registry]] | year = 1997 | title = Toxicological Profile for Tetrachloroethene | url = http://www.atsdr.cdc.gov/toxprofiles/tp18.html}}

* {{cite journal | author = Doherty, R.E. | year = 2000 | title = 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 = [[Journal of Environmental Forensics]] | volume = 1 | pages = 69–81 | doi = 10.1006/enfo.2000.0010 }}

* [http://www.atsdr.cdc.gov/csem/pce/ ATSDR Case Studies in Environmental Medicine: Tetrachloroethylene Toxicity] U.S. [[Department of Health and Human Services]]

* Australian [http://www.npi.gov.au/database/substance-info/profiles/80.html National Pollutant Inventory (NPI)] page

* [http://www.nydailynews.com/news/crime_file/2007/04/20/2007-04-20_toxic_fumes_may_have_made_gunman_snap-1.html "Toxic Fumes May Have Made Gunman Snap"], by Julian Kesner, New York ''Daily News'', April 20, 2007.

[[Category:Organochlorides]]

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