Tetrafluoroethylene 2882473 223831951 2008-07-06T01:19:21Z Wizard191 935746 /* Manufacture */ rmv [CF<sub>2</sub>] → because it doesn't balance {{Chembox new | Name = Tetrafluoroethylene | ImageFile = Tetrafluoroethylene.png <!-- | ImageSize = 100px --> | ImageName = Tetrafluoroethylene | ImageFile1 = Tetrafluoroethylene3D.png <!-- | ImageSize1 = 100px --> | ImageName1 = Tetrafluoroethylene | IUPACName = tetrafluoroethene | OtherNames = perfluoroethylene<br />TFE | Section1 = {{Chembox Identifiers | CASNo = 116-14-3 | SMILES = FC(F)=C(F)F }} | Section2 = {{Chembox Properties | Formula = C<sub>2</sub>F<sub>4 | MolarMass = 100.02 g/mol | Density = 1.519 g/cm³ at -76 °C | MeltingPt = -142.5 °C | BoilingPt = -76.3 °C }} }} '''Tetrafluoroethylene''' (TFE) is a [[chemical compound]] with the formula C<sub>2</sub>F<sub>4</sub>. It is the simplest unsaturated [[perfluorocarbon]]. This gaseous species is used primarily in the industrial preparation of [[polymer]]s. In organic chemistry, tetrafluoroethylene is a potent [[dienophile]]. ==Properties== Tetrafluoroethylene is a colourless, odourless gas. Like all unsaturated fluorocarbons it is susceptible to [[nucleophilic]] attack. It is unstable towards decomposition to C and CF<sub>4</sub> and prone to form explosive peroxides in contact with air. <ref>US Patent 5,345,013, issued to du Pont de Nemours</ref> ==Industrial use== Polymerization of tetrafluoroethylene produces [[polytetrafluoroethylene]] (PTFE) polymers such as Teflon. PTFE is one of the two fluorocarbon resins composed wholly of fluorine and carbon. The other resin composed purely of carbon and fluorine is the copolymer of TFE with typically 6-9% hexafluoropropene (HFP), which is known as FEP (fluorinated ethylene propylene copolymer). TFE is also used in the preparation of numerous copolymers that also include hydrogen and/or oxygen, including both fluoroplastics and fluoroelastomers. Typical TFE-based fluoroplastics include ETFE, the alternating 1:1 copolymer with ethylene, and PFA, which is a random copolymer similar to FEP but with a minor amount of a perfluoroalkyl vinyl ether (PAVE)rather than HFP. DuPont uses primarily perfluoro(methylvinylether), whereas Daikin uses primarily perfluoro(propylvinylether) in manufacturing PFA. There are numerous other fluoropolymers that contain TFE, but usually not at greater than 50% by weight. ==Manufacture== TFE is manufactured from [[chloroform]].<ref>{{cite journal |abstract=[http://www.bepress.com/ijcre/vol2/A6/] |author=Dae Jin Sung, Dong Ju Moon, Yong Jun Lee, Suk-In Hong |title=Catalytic Pyrolysis of Difluorochloromethane to Produce Tetrafluoroethylene |journal=International Journal of Chemical Reactor Engineering |year=2004 |volume=2 |pages=A6 }}</ref> Chloroform is fluorinated by reaction with [[hydrogen fluoride]] to produce [[chlorodifluoromethane]] (R-22). Pyrolysis of chlorodifluoromethane then yields TFE, with [[difluorocarbene]] as an intermediate. :CHCl<sub>3</sub> + 2 HF → CHClF<sub>2</sub> + 2 HCl :2 CHClF<sub>2</sub> → C<sub>2</sub>F<sub>4</sub> + 2 HCl The reverse reaction – vacuum pyrolysis of PTFE at 600–650 °C in a [[Fused quartz|quartz vessel]] – is a convenient laboratory synthesis of TFE. The PTFE polymer [[cracking (chemistry)|cracks]], and at a pressure below 5 torr exclusively C<sub>2</sub>F<sub>4</sub> is obtained. At higher pressures the product mixture contains [[hexafluoropropene]] and octafluorocyclobutane. <ref>Hunadi, R. J.; Baum, K. “Tetrafluoroethylene: A Convenient Laboratory Preparation Synthesis 1982, page 454.</ref> ==Safety== TFE is an alkylating agent, albeit a weak one, and as such is expected to be carcinogenic. LD<sub>50</sub>(rat, inhalation) = 40000 ppm.<ref>[http://ntp-server.niehs.nih.gov/ntp/roc/eleventh/profiles/s170tfe.pdf#search=%22tetrafluoroethylene%22 NIH Substance Profile for TFE]</ref>. The compound is best handled diluted with an inert gas, as localized heating can provoke explosive decomposition to C and CF<sub>4</sub>. When working with TFE oxygen must be scrupulously excluded when handling the compound, as it catalyzes autopolymerization, which can take place with great force. ==See also== *[[Tetrachloroethylene]] *[[1,1,1,2-Tetrafluoroethane]] ==References== {{reflist}} ==External links== *[http://www.mindfully.org/Plastic/Teflon/Tetrafluoroethylene-NTP-Data.htm National Toxicology Program Chemical Repository] *[http://www.zeusinc.com/pdf/Zeus_Introduction_to_THV.pdf Tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride terpolymer -- aka THV, melt-processable members of the fluorocarbon family] [[Category:Organofluorides]] [[Category:Monomers]] [[de:Tetrafluorethylen]] [[es:Tetrafluoroetileno]] [[fr:Tétrafluoroéthylène]] [[it:Tetrafluoroetene]] [[ja:テトラフルオロエチレン]] [[pl:Tetrafluoroeten]] [[sv:Tetrafluoreten]]