Tetrafluoroethylene

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Tetrafluoroethylene
Tetrafluoroethylene Tetrafluoroethylene.svg
Tetrafluoroethylene
Tetrafluoroethylene Tetrafluoroethylene-3D-vdW.png
Tetrafluoroethylene
Names
Preferred IUPAC name
Tetrafluoroethene
Other names
perfluoroethylene
TFE
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.752 OOjs UI icon edit-ltr-progressive.svg
KEGG
PubChem CID
UNII
  • InChI=1S/C2F4/c3-1(4)2(5)6 Yes check.svgY
    Key: BFKJFAAPBSQJPD-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C2F4/c3-1(4)2(5)6
    Key: BFKJFAAPBSQJPD-UHFFFAOYAC
  • FC(F)=C(F)F
Properties
C2F4
Molar mass 100.02 g/mol
AppearanceColorless gas
Odor Odorless
Density 1.519 g/cm3 at −76 °C
Melting point −142.5 °C (−224.5 °F; 130.7 K)
Boiling point −76.3 °C (−105.3 °F; 196.8 K)
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
4
3
OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Tetrafluoroethylene (TFE) is a fluorocarbon with the chemical formula C 2 F 4. It is the simplest perfluorinated alkene. This gaseous species is used primarily in the industrial preparation of fluoropolymers.

Contents

It was first reported as "dicarbon tetrafluoride" in 1890. [2]

Properties

Tetrafluoroethylene is a synthetic colorless, odorless gas that is insoluble in water. Like all unsaturated fluorocarbons, it is susceptible to nucleophilic attack. It is unstable towards decomposition to carbon and carbon tetrafluoride (CF
4
) and prone to form explosive peroxides in contact with air. [3] [4]

Industrial use

Polymerization of tetrafluoroethylene produces polytetrafluoroethylene (PTFE) polymers such as Teflon and Fluon. 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 tetrafluoroethylene, but usually not at greater than 50% by weight.

Manufacture

TFE is manufactured from chloroform. [5] Chloroform is fluorinated by reaction with hydrogen fluoride to produce chlorodifluoromethane (R-22). Pyrolysis of chlorodifluoromethane (at 550–750 °C) yields TFE, with difluorocarbene as an intermediate.

CHCl3 + 2 HF → CHClF2 + 2 HCl
2 CHClF2 → C2F4 + 2 HCl

Alternatively, it can be prepared by pyrolysis of fluoroform (which is also produced from chloroform and HF):

2 CHF3 → C2F4 + 2 HF

Laboratory methods

A convenient, safe method for generating TFE is the pyrolysis of the sodium salt of pentafluoropropionic acid: [6]

C2F5CO2Na → C2F4 + CO2 + NaF

The depolymerization reaction – vacuum pyrolysis of PTFE at 650–700 °C (1,200–1,290 °F) in a quartz vessel – is a traditional laboratory synthesis of TFE. The process is however challenging because attention must be paid to pressure, as well as the avoidance of perfluoroisobutylene. PTFE polymer cracks, and at a pressure below 5  Torr (670  Pa ) exclusively C2F4 is obtained. At higher pressures the product mixture contains hexafluoropropylene and octafluorocyclobutane. [7]

Reactions

Tetrafluoroethylene is a reactive molecule that participates in myriad reactions. Owing to the presence of four fluorine substituents, its reactions differ strongly from the behavior of conventional alkenes such as ethylene. Tetrafluoroethylene dimerizes, giving octafluorocyclobutane. Even normal alkenes and dienes add tetrafluoroethylene in a [2+2] manner. 1,3-Butadiene gives 3-vinyl-1,1,2,2-tetrafluorocyclobutane. [8]

Safety

The main hazard associated with TFE is that of explosion, especially if oxygen is present. TFE reacts with oxygen at low temperatures to form an explosive oxide, [3] the detonation of which is usually sufficient to trigger explosive decomposition of TFE to C and CF4. [9] Explosions can also be caused by adiabatic compression if the TFE is handled under high pressure, which it typically is in an industrial setting. If pressurised TFE is allowed into a vessel or pipework at a lower pressure, then the atmosphere in the vessel will be compressed by the TFE, causing it to heat up, potentially to the point where it might detonate the TFE. This has been known to cause explosions. [10] In industry, pipework is flushed with pressurized nitrogen, before the introduction of TFE, both to exclude oxygen and prevent adiabatic compression.

TFE is an alkylating agent, albeit a weak one, and as such is expected to be a carcinogen. LD50(rat, inhalation) = 40000 ppm. [11]

The International Agency for Research on Cancer classifies TFE as probably carcinogenic to humans based on animal studies. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Polytetrafluoroethylene</span> Synthetic polymer

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally discovered the compound in 1938.

<span class="mw-page-title-main">Fluorocarbon</span> Class of chemical compounds

Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are commercial polymers, refrigerants, drugs, and anesthetics.

A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon," trademarked by the DuPont Company.

In chemistry, trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane are replaced by halogen atoms. Trihalomethanes with all the same halogen atoms are called haloforms. Many trihalomethanes find uses in industry as solvents or refrigerants. Some THMs are also environmental pollutants, and few are considered carcinogenic.

<span class="mw-page-title-main">Fluorinated ethylene propylene</span> Polymer

Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the polytetrafluoroethylene (PTFE) resins in that it is melt-processable using conventional injection molding and screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.

<span class="mw-page-title-main">Hydrogen fluoride</span> Chemical compound

Hydrogen fluoride (fluorane) is an inorganic compound with chemical formula HF. It is a very poisonous, colorless gas or liquid that dissolves in water to yield an aqueous solution termed hydrofluoric acid. It is the principal industrial source of fluorine, often in the form of hydrofluoric acid, and is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers, e.g. polytetrafluoroethylene (PTFE). HF is also widely used in the petrochemical industry as a component of superacids. Due to strong and extensive hydrogen bonding, it boils at near room temperature, much higher than other hydrogen halides.

FKM is a family of fluorocarbon-based fluoroelastomer materials defined by ASTM International standard D1418, and ISO standard 1629. It is commonly called fluorine rubber or fluoro-rubber. FKM is an abbreviation of Fluorine Kautschuk Material. All FKMs contain vinylidene fluoride as the common monomer, to which different other monomers are added for specific types and functionalities, fitting the desired application.

<span class="mw-page-title-main">Carbon monofluoride</span> Chemical compound

Carbon monofluoride (CF, CFx, or (CF)n), also called polycarbon monofluoride (PMF), polycarbon fluoride, poly(carbon monofluoride), and graphite fluoride, is a material formed by high-temperature reaction of fluorine gas with graphite, charcoal, or pyrolytic carbon powder. It is a highly hydrophobic microcrystalline powder. Its CAS number is 51311-17-2. In contrast to graphite intercalation compounds it is a covalent graphite compound.

Organofluorine chemistry describes the chemistry of organofluorine compounds, organic compounds that contain a carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refrigerants, and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity. The area of organofluorine chemistry often requires special techniques associated with the handling of fluorinating agents.

Perfluoroethers are a class of organofluorine compound containing one or more ether functional group. In general these compounds are structurally analogous to the related hydrocarbon ethers, except for the distinctive properties of fluorocarbons.

The Fowler process is an industry and laboratory route to fluorocarbons, by fluorinating hydrocarbons or their partially fluorinated derivatives in the vapor phase over cobalt(III) fluoride.

<span class="mw-page-title-main">Hexafluoropropylene oxide</span> Chemical compound

Hexafluoropropylene oxide (HFPO) is an intermediate used in industrial organofluorine chemistry; specifically it is a monomer for fluoropolymers. This colourless gas is the epoxide of hexafluoropropylene, which is a fluorinated analog of propylene oxide, HFPO is produced by DuPont and 3M and as a precursor to the lubricant Krytox and related materials. It is generated by oxidation of perfluoropropylene, e.g. with oxygen as well as other oxidants.

<span class="mw-page-title-main">Fluorine</span> Chemical element, symbol F and atomic number 9

Fluorine is a chemical element; it has symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. Fluorine is extremely reactive, as it reacts with all other elements except for the light inert gases.

<span class="mw-page-title-main">Fluorine perchlorate</span> Chemical compound

Fluorine perchlorate, also called perchloryl hypofluorite is the rarely encountered chemical compound of fluorine, chlorine, and oxygen with the chemical formula ClO
4
F
or FOClO
3
. It is an extremely unstable gas that explodes spontaneously and has a penetrating odor.

Electrochemical fluorination (ECF), or electrofluorination, is a foundational organofluorine chemistry method for the preparation of fluorocarbon-based organofluorine compounds. The general approach represents an application of electrosynthesis. The fluorinated chemical compounds produced by ECF are useful because of their distinctive solvation properties and the relative inertness of carbon–fluorine bonds. Two ECF synthesis routes are commercialized and commonly applied: the Simons process and the Phillips Petroleum process. It is also possible to electrofluorinate in various organic media. Prior to the development of these methods, fluorination with fluorine, a dangerous oxidizing agent, was a dangerous and wasteful process. ECF can be cost-effective, but it may also result in low yields.

Difluorocarbene is the chemical compound with formula CF2. It has a short half-life, 0.5 and 20 ms, in solution and in the gas phase, respectively. Although highly reactive, difluorocarbene is an intermediate in the production of tetrafluoroethylene, which is produced on an industrial scale as the precursor to Teflon (PTFE).

Fluorine forms a great variety of chemical compounds, within which it always adopts an oxidation state of −1. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Most frequently, covalent bonds involving fluorine atoms are single bonds, although at least two examples of a higher order bond exist. Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding. Fluorine's chemistry includes inorganic compounds formed with hydrogen, metals, nonmetals, and even noble gases; as well as a diverse set of organic compounds. For many elements the highest known oxidation state can be achieved in a fluoride. For some elements this is achieved exclusively in a fluoride, for others exclusively in an oxide; and for still others the highest oxidation states of oxides and fluorides are always equal.

<span class="mw-page-title-main">Fluorochemical industry</span> Industry dealing with chemicals from fluorine

The global market for chemicals from fluorine was about US$16 billion per year as of 2006. The industry was predicted to reach 2.6 million metric tons per year by 2015. The largest market is the United States. Western Europe is the second largest. Asia Pacific is the fastest growing region of production. China in particular has experienced significant growth as a fluorochemical market and is becoming a producer of them as well. Fluorite mining was estimated in 2003 to be a $550 million industry, extracting 4.5 million tons per year.

<span class="mw-page-title-main">Perfluoroalkoxy alkane</span> Family of polymers

Perfluoroalkoxy alkanes (PFA) are fluoropolymers. They are copolymers of tetrafluoroethylene (C2F4) and perfluoroethers (C2F3ORf, where Rf is a perfluorinated group such as trifluoromethyl (CF3)). The properties of these polymers are similar to those of polytetrafluoroethylene (PTFE). Compared to PTFE, PFA has better anti-stick properties and higher chemical resistance, at the expense of lesser scratch resistance.

1,2-Difluoroethane is a saturated hydrofluorocarbon containing an atom of fluorine attached to each of two carbons atoms. The formula can be written CH2FCH2F. It is an isomer of 1,1-difluoroethane. It has a HFC name of HFC-152 with no letter suffix. When cooled to cryogenic temperatures it can have different conformers, gauche and trans. In the liquid form these are about equally abundant and easily interconvert. As a gas it is mostly the gauche form.

References

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  2. C. Chabrie "General Method for the Preparation of Carbon Fluorides" in Journal - Chemical Society, London. (1890). UK: Chemical Society.
  3. 1 2 Gozzo, F.; Camaggi, G. (January 1966). "Oxidation reactions of tetrafluoroethylene and their products—I". Tetrahedron. 22 (6): 1765–1770. doi:10.1016/S0040-4020(01)82248-1.
  4. PubChem. "Tetrafluoroethylene". pubchem.ncbi.nlm.nih.gov. Retrieved 2023-09-25.
  5. Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine; Kirschtitle=Fluorine Compounds, Organic, Peer (2016). Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349.pub2. ISBN   978-3527306732.
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  11. NIH Substance Profile for TFE
  12. "Terrafluoroethylene" (PDF). International Agency for Research on Cancer. Retrieved 20 May 2020.[ permanent dead link ]