Tetrafluoroethylene (TFE) is a

fluorocarbon 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 ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. It is a colorless gas. Its structure is . It is used primarily in the industrial preparation of fluoropolymers. It is the simplest perfluorinated

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

. It was first reported as "dicarbon tetrafluoride" in 1890.

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 Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

and carbon tetrafluoride () and prone to form explosive peroxides in contact with air.

Industrial use

Polymerization of tetrafluoroethylene produces

polytetrafluoroethylene 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 corporate spin-of ...

(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 In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

of TFE with typically 6–9% hexafluoropropene (HFP), which is known as FEP (

fluorinated ethylene propylene 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 Plastic extrusio ...

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 Dupont, DuPont, Du Pont, duPont, or du Pont may refer to: People * Dupont (surname) Dupont, also spelled as DuPont, duPont, Du Pont, or du Pont is a French surname meaning "of the bridge", historically indicating that the holder of the surname re ...

uses primarily perfluoro(methylvinylether), whereas

Daikin is a Japanese multinational conglomerate company headquartered in Osaka. Daikin is the world's largest air conditioner manufacturer. History Daikin Industries Ltd was founded in 1924 as by Akira Yamada. In 1953, Daiflon or polychloro ...

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 Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

. Chloroform is fluorinated by reaction with

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

to produce chlorodifluoromethane (R-22).

Pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

of chlorodifluoromethane (at 550–750 °C) yields TFE, with difluorocarbene as an intermediate. : : Alternatively, it can be prepared by pyrolysis of fluoroform (which is also produced from chloroform and HF): :

Laboratory methods

A convenient, safe method for generating TFE is the

pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...

of the

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

of pentafluoropropionic acid: : The depolymerization reaction – vacuum pyrolysis of PTFE at 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 perfluoroisobutene. PTFE polymer cracks, and at a pressure below exclusively is obtained. At higher pressures the product mixture contains hexafluoropropylene and octafluorocyclobutane.

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 Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

. Tetrafluoroethylene dimerizes, giving octafluorocyclobutane. Even normal alkenes and dienes add tetrafluoroethylene in a +2manner. 1,3-Butadiene gives 3-vinyl-1,1,2,2-tetrafluorocyclobutane.

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, the detonation of which is usually sufficient to trigger explosive decomposition of TFE to C and . 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. 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. The

International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; ) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and coordinate research into the causes of cancer. It also cance ...

classifies TFE as probably carcinogenic to humans based on animal studies.

References

External links

National Toxicology Program Chemical RepositoryTetrafluoroethylene, hexafluoropropylene and vinylidene fluoride terpolymer – aka THV, melt-processable members of the fluorocarbon family
* {{Authority control Perfluoroalkenes Monomers IARC Group 2A carcinogens Organic compounds with 2 carbon atoms