View source for Fluorocarbon

{{Short description|Class of chemical compounds}}
[[File:FluorocarbonCrabFish.JPG|thumb|alt=Beaker with two layers of liquid, goldfish and crab in top, coin sunk in the bottom|[[miscibility|Immiscible]] layers of colored water (top) and much denser [[perfluoroheptane]] (bottom) in a beaker; a goldfish and crab cannot penetrate the boundary; [[coin]]s rest at the bottom.]]

'''Fluorocarbons''' are [[chemical compound]]s with [[carbon-fluorine bond]]s.  Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced{{clarify|date=September 2023}} stability, volatility, and hydrophobicity.  Several fluorocarbons and their derivatives are commercial [[fluoropolymer|polymers]], [[refrigerants]], [[drug]]s, and [[anesthetic]]s.<ref name=Lemal>
{{cite journal
 |author=Lemal DM
 |title=Perspective on fluorocarbon chemistry
 |journal=J. Org. Chem.
 |volume=69 |issue=1 |pages=1–11 |date=January 2004
 |pmid=14703372
 |doi=10.1021/jo0302556
}}
</ref>

==Nomenclature==
'''Perfluorocarbons''' or '''PFCs''', are [[organofluorine]] compounds with the formula C<sub>x</sub>F<sub>y</sub>, meaning they contain only [[carbon]] and [[fluorine]].<ref name="ReferenceA">{{GoldBookRef |title= fluorocarbons |file= F02459}}</ref> The terminology is not strictly followed and many fluorine-containing organic compounds are  also called fluorocarbons.<ref name=Lemal/> Compounds with the prefix '''perfluoro-''' are hydrocarbons, including those with heteroatoms, wherein all C-H bonds have been replaced by C-F bonds.<ref name=Murphy>
{{cite journal
 |author=Murphy WJ
 |title=Fluorine Nomenclature... A statement by the Editors
 |journal=Ind. Eng. Chem.
 |volume=39
 |issue=3
 |pages=241–242
 |date=March 1947
 |doi=10.1021/ie50447a004
}}
</ref> Fluorocarbons includes perfluoroalkanes, fluoroalkenes, fluoroalkynes, and perfluoroaromatic compounds.

==Perfluoroalkanes==
===Chemical properties===
Perfluoroalkanes are very stable because of the strength of the [[carbon–fluorine bond]], one of the strongest in organic chemistry.<ref name=hagan>
{{cite journal
 |author=O'Hagan D
 |title=Understanding organofluorichemistry. An introduction to the C–F bond
 |journal=Chem. Soc. Rev.
 |date=February 2008
 |volume=37
 |issue=2
 |pages=308–19
 |pmid=18197347
 |doi=10.1039/b711844a
}}
</ref>
Its strength is a result of the electronegativity of fluorine imparting partial ionic character through [[partial charge]]s on the carbon and fluorine atoms, which shorten and strengthen the bond (compared to carbon-hydrogen bonds) through favorable [[covalent]] interactions. Additionally, multiple carbon–fluorine bonds increase the strength and stability of other nearby carbon–fluorine bonds on the same [[geminal]] carbon, as the carbon has a higher positive partial charge.<ref name=Lemal/> Furthermore, multiple carbon–fluorine bonds also strengthen the "skeletal" carbon–carbon bonds from the [[inductive effect]].<ref name=Lemal/> Therefore, [[Saturated and unsaturated compounds|saturated]] fluorocarbons are more chemically and thermally stable than their corresponding hydrocarbon counterparts, and indeed any other organic compound. They are susceptible to attack by very strong reductants, e.g. [[Birch reduction]] and very specialized organometallic complexes.<ref name=kip>
{{cite journal
 |vauthors=Kiplinger JL, Richmond TG, Osterberg CE
 |title=Activation of Carbon-Fluorine Bonds by Metal Complexes
 |journal=Chem. Rev.
 |volume=94
 |issue=2
 |pages=373–431
 |year=1994
 |doi=10.1021/cr00026a005
 }}
</ref>

Fluorocarbons are colorless and have high density, up to over twice that of water. They are not miscible with most organic solvents (e.g., ethanol, acetone, ethyl acetate, and chloroform), but are miscible with some hydrocarbons (e.g., hexane in some cases). They have very low solubility in water, and water has a very low solubility in them (on the order of 10 ppm). They have low [[refractive index|refractive indices]].

{{Image frame|content=<chem>\overset{\delta+}{C}-\overset{\delta-}{F}</chem>|caption=The partial charges in the polarized carbon–fluorine bond|width=150}}

As the high [[electronegativity]] of fluorine reduces the [[polarizability]] of the atom,<ref name=Lemal/> fluorocarbons are only weakly susceptible to the fleeting dipoles that form the basis of the [[London dispersion force]]. As a result, fluorocarbons have low intermolecular attractive forces and are [[lipophobic]] in addition to being [[hydrophobe|hydrophobic]] and [[non-polar]]. Reflecting the weak [[intermolecular force]]s these compounds exhibit low [[viscosity|viscosities]] when compared to liquids of similar [[boiling point]]s, low [[surface tension]] and low [[heat of vaporization|heats of vaporization]]. The low [[attractive force]]s in fluorocarbon liquids make them [[compressible]] (low [[bulk modulus]]) and able to dissolve gas relatively well. Smaller fluorocarbons are extremely [[volatility (chemistry)|volatile]].<ref name=Lemal/> There are five perfluoroalkane gases: [[tetrafluoromethane]] (bp −128&nbsp;°C), [[hexafluoroethane]] (bp −78.2&nbsp;°C), [[octafluoropropane]] (bp −36.5&nbsp;°C), [[perfluorobutane|perfluoro-n-butane]] (bp −2.2&nbsp;°C) and perfluoro-iso-butane (bp −1&nbsp;°C). Nearly all other fluoroalkanes are liquids; the most notable exception is [[perfluorocyclohexane]], which [[sublimation (chemistry)|sublimes]] at 51&nbsp;°C.<ref>{{cite web |url=http://www.ornl.gov/~webworks/cpr/v823/rpt/108771.pdf |title=Archived copy |access-date=2008-11-29 |url-status=dead |archive-url=https://web.archive.org/web/20081205213815/http://www.ornl.gov/~webworks/cpr/v823/rpt/108771.pdf |archive-date=2008-12-05 }}</ref> Fluorocarbons also have low [[surface energy|surface energies]] and high [[dielectric]] strengths.<ref name=Lemal/>

<gallery caption="Perfluoroalkanes" widths="150px" heights="120px" perrow="5">
File:Tetrafluormethan.svg|[[Carbon tetrafluoride]], the simplest perfluoroalkane
File:Perfluorooctane.png|[[Perfluorooctane]], a linear perfluoroalkane
File:Perfluoro(2-methylpentane).svg|[[Perfluoro-2-methylpentane]], a branched perfluoroalkane
File:Perfluoro-1,3-dimethylcyclohexane.svg|[[Perfluoro-1,3-dimethylcyclohexane]], a cyclic perfluoroalkane
File:Perfluorodecaline.svg|[[Perfluorodecalin]], a polycyclic perfluoroalkane
</gallery>

===Flammability===
In the 1960s there was a lot of interest in fluorocarbons as anesthetics. The research did not produce any anesthetics, but the research included tests on the issue of flammability, and showed that the tested fluorocarbons were not flammable in air in any proportion, though most of the tests were in pure [[oxygen]] or pure [[nitrous oxide]] (gases of importance in anesthesiology).<ref>
{{cite journal
 |author=Larsen ER
 |title=Fluorine Compounds in Anesthesiology: VI Flammability
 |journal=Fluorine Chem. Rev.
 |volume=3
 |year= 1969
 |pages=22–27
}}
</ref><ref>
{{cite tech report
 |title=Flutec
 |year=1982
 |institution=ISC Chemicals Limited
}}
</ref>

{| class="wikitable"
|-
! Compound
! Test conditions
! Result
|-
| [[Hexafluoroethane]]
| Lower flammability limit in oxygen
| None
|-
| rowspan="3" | [[Perfluoropentane]]
| [[Flash point]] in air
| None
|-
| Flash point in oxygen
| −6&nbsp;°C
|-
| Flash point nitrous oxide
| −32&nbsp;°C
|-
| rowspan="4" | [[Perfluoromethylcyclohexane]]
| Lower flammability limit in air
| None
|-
| Lower flammability limit in oxygen
| 8.3%
|-
| Lower flammability limit in oxygen (50&nbsp;°C)
| 7.4%
|-
| Lower flammability limit in nitrous oxide
| 7.7%
|-
| [[Perfluoro-1,3-dimethylcyclohexane]]
| Lower flammability limit in oxygen (50&nbsp;°C)
| 5.2%
|-
| rowspan="3" | [[Perfluoromethyldecalin]]
| Spontaneous ignition test<br />in oxygen at 127 bar
| No ignition at 500&nbsp;°C
|-
| Spontaneous ignition in adiabatic shock<br />wave in oxygen, 0.98 to 186 bar
| No ignition
|-
| Spontaneous ignition in adiabatic shock<br />wave in oxygen, 0.98 to 196 bar
| Ignition
|}

In 1993, 3M considered fluorocarbons as fire extinguishants to replace CFCs.<ref>{{cite web|url=https://www.nist.gov/el/fire_research/upload/R9302960.pdf|title=Development of Perfluorocarbons As Clean Extinguishing Agents|author1=John A. Pignato, Jr.|author2=Paul E. Rivers|author3=Myron T. Pike|publisher=National Institute of Standards and Technology|url-status=dead|archive-url=https://web.archive.org/web/20140521123729/https://www.nist.gov/el/fire_research/upload/R9302960.pdf|archive-date=2014-05-21|access-date=2019-01-03}}</ref> This extinguishing effect has been attributed to their high [[heat capacity]], which takes heat away from the fire. It has been suggested that an atmosphere containing a significant percentage of perfluorocarbons on a space station or similar would prevent fires altogether.<ref>{{cite journal
 |author=McHale ET
 |title=Life Support Without Combustion Hazards
 |journal=[[Fire Technology]]
 |volume=10 |issue=1 |pages=15–24 |year=1974 |doi=10.1007/bf02590509|s2cid=111161665
 }}</ref>
<ref>{{cite journal
 |author=Huggett C
 |title=Habitable Atmospheres Which Do Not Support Combustion
 |journal=Combustion and Flame
 |volume=20 |pages=140–142 |year= 1973
 |doi=10.1016/s0010-2180(73)81268-4}}</ref>
When combustion does occur, toxic fumes result, including [[carbonyl fluoride]], [[carbon monoxide]], and [[hydrogen fluoride]].

===Gas dissolving properties===
Perfluorocarbons dissolve relatively high volumes of gases. The high solubility of gases is attributed to the weak intermolecular interactions in these fluorocarbon fluids.<ref>{{cite web |title=Dissolving gases in FLUTEC liquids |publisher=F2 Chemicals Ltd |date=2005-05-10 |url=http://www.f2chemicals.com/pdf/technical/Gas%20solubility.pdf}}</ref>

The table shows values for the mole fraction, {{mvar|x}}{{sub|1}}, of nitrogen dissolved, calculated from the [[Blood–gas partition coefficient]], at 298.15&nbsp;K (25&nbsp;°C), 0.101325&nbsp;MPa.<ref>{{cite journal |vauthors=Battino R, Rettich TR, Tominaga T |year=1984 |title=The solubility of nitrogen and air in liquids |journal=J. Phys. Chem. Ref. Data |volume=13 |issue=2 |pages=308–319 |doi=10.1063/1.555713 |bibcode=1984JPCRD..13..563B }}</ref>

{| class="wikitable"
|-
!style="text-align:right;"| Liquid  
! 10{{sup|4}}{{mvar|x}}{{sub|1}}
! Concentration<br/>( mM )
|-
|style="text-align:right;"| [[Water]]  
| {{figure space}}0.118
| {{figure space}}0.65
|-
|style="text-align:right;"| [[Ethanol]]  
| {{figure space}}3.57
| {{figure space}}6.12
|-
|style="text-align:right;"| [[Tetrahydrofuran]]  
| {{figure space}}5.21
| {{figure space}}6.42
|-
|style="text-align:right;"| [[Acetone]]  
| {{figure space}}5.42
| {{figure space}}7.32
|-
|style="text-align:right;"| [[Cyclohexane]]  
| {{figure space}}7.73
| {{figure space}}7.16
|-
|style="text-align:right;"|  [[Perfluoro-1,3-dimethylcyclohexane]]  
| 31.9
| 14.6
|-
|style="text-align:right;"| [[Perfluoromethylcyclohexane]]  
| 33.1
| 16.9
|}

===Manufacture===
The development of the fluorocarbon industry coincided with [[World War II]].<ref name=McBee>{{cite journal
 |author=McBee ET
 |title=Fluorine Chemistry
 |journal=Ind. Eng. Chem.
 |volume=39 |issue=3 |pages=236–237 |date=March 1947 |doi=10.1021/ie50447a002}}</ref> Prior to that, fluorocarbons were prepared by reaction of fluorine with the hydrocarbon, i.e., direct fluorination. Because C-C bonds are readily cleaved by fluorine, direct fluorination mainly affords smaller perfluorocarbons, such as tetrafluoromethane, hexafluoroethane, and octafluoropropane.<ref name="Ullmann">{{Cite encyclopedia |title=Fluorine Compounds, Organic |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |doi=10.1002/14356007.a11_349 |isbn=978-3-527-30385-4 |last2=Schwertfeger |first2=Werner |last3=Feiring |first3=Andrew |last4=Smart |first4=Bruce |last5=Behr |first5=Fred |last6=Vogel |first6=Herward |last7=McKusick |first7=Blaine |last1=Siegemund |first1=Günter}}</ref>

====Fowler process====
A major breakthrough that allowed the large scale manufacture of fluorocarbons was the [[Fowler process]]. In this process, [[cobalt trifluoride]] is used as the source of fluorine. Illustrative is the synthesis of [[perfluorohexane]]:
:{{chem2|C6H14 + 28 CoF3 -> C6F14 + 14 HF + 28 CoF2}}

The resulting cobalt difluoride is then regenerated, sometimes in a separate reactor:
:{{chem2|2 CoF2 + F2 -> 2 CoF3}}

Industrially, both steps are combined, for example in the manufacture of the Flutec range of fluorocarbons by F2 chemicals Ltd, using a vertical stirred bed reactor, with hydrocarbon introduced at the bottom, and fluorine introduced halfway up the reactor. The fluorocarbon vapor is recovered from the top.

====Electrochemical fluorination====
[[Electrochemical fluorination]] (ECF) (also known as the Simons' process) involves [[electrolysis]] of a substrate dissolved in [[hydrogen fluoride]]. As fluorine is itself manufactured by the electrolysis of hydrogen fluoride, ECF is a rather more direct route to fluorocarbons. The process proceeds at low voltage (5 – 6 V) so that free fluorine is not liberated. The choice of substrate is restricted as ideally it should be soluble in hydrogen fluoride. Ethers and tertiary amines are typically employed. To make perfluorohexane, trihexylamine is used, for example:

:{{chem2|N(C6H13)3 + 45 HF -> 3 C6F14 + NF3 + 42 H2}}

The perfluorinated amine will also be produced:
:{{chem2|N(C6H13)3 + 39 HF -> N(C6F13)3 + 39 H2}}

===Environmental and health concerns===
Fluoroalkanes are generally inert and non-toxic.<ref>{{cite web |url=http://www.fluorocarbons.org/chemical-families/pfcs/pfc-toxicological-profile |title=EFCTC - Toxicological profiles of PFCS Perfluorocarbons |access-date=2014-05-19 |url-status=dead |archive-url=https://web.archive.org/web/20150924013903/http://www.fluorocarbons.org/chemical-families/pfcs/pfc-toxicological-profile |archive-date=2015-09-24 }}</ref><ref>{{cite web|url=https://www.epa.gov/HPV/pubs/summaries/perfluro/c13244tp.pdf|title=HPV Robust Summaries and Test Plan|url-status=dead|archive-url=https://web.archive.org/web/20121202022600/https://www.epa.gov/HPV/pubs/summaries/perfluro/c13244tp.pdf|publisher=Internet Archive|archive-date=2012-12-02|access-date=2019-01-03}}</ref><ref name=Yamanouchi>{{cite journal |author1=Yamanouchi K|author2=Yokoyama K|journal=Proceedings of the Xth International Congress for Nutrition, Kyoto |title=Symposium on Perfluorochemical Artificial Blood |pages=91 |year=1975}}</ref>

Fluoroalkanes are not [[ozone depletion|ozone depleting]], as they contain no chlorine or bromine atoms, and they are sometimes used as replacements for ozone-depleting chemicals.<ref>{{Cite web |url=http://www.expertglossary.com/climate-change/definition/perfluorocarbons-pfcs |title=Perfluorocarbons (PFCS) definition - ExpertGlossary |access-date=2022-12-14 |archive-date=2014-05-19 |archive-url=https://web.archive.org/web/20140519132431/http://www.expertglossary.com/climate-change/definition/perfluorocarbons-pfcs |url-status=dead }}</ref>
The term fluorocarbon is used rather loosely to include any chemical containing fluorine and carbon, including [[chlorofluorocarbon]]s, which are ozone depleting.

Perfluoroalkanes used in medical procedures are rapidly excreted from the body, primarily via expiration with the rate of excretion as a function of the vapour pressure; the half-life for [[octafluoropropane]] is less than 2 minutes,<ref name=platts>{{cite journal | author1=Platts DG|author2=Fraser JF|title = Contrast Echocardiography in Critical Care: Echoes of the Future?: A Review of the Role of Microsphere Contrast Echocardiography|journal=Critical Care and Resuscitation |volume=13 |year= 2011 |issue=1 |pages= 44–55 |pmid=21355829 }}</ref> compared to about a week for perfluorodecalin.<ref name=Geyer>{{cite journal |author=Geyer RP |journal=Proc. Xth Intern. Congress for Nutr., Kyoto |title=Symp on Perfluorochemical Artif. Blood |pages=3–19 |year=1975}}</ref>

[[Image:Halogenated gas concentrations 1978-present.png|thumb|right|upright=2.2|Atmospheric concentration of PFC-14 and PFC-116 compared to similar man-made halogenated gases between years 1978 and 2015 (right graph). Note the logarithmic scale.]]
Low-boiling perfluoroalkanes are potent [[greenhouse gases]], in part due to their very long atmospheric lifetime, and their use is covered by the [[Kyoto Protocol]].{{citation needed|date=May 2017}}<ref>{{Cite web|url=http://unfccc.int/kyoto_protocol/items/2830.php|title=Kyoto Protocol|last=Change|first=United Nations Framework Convention on Climate|website=unfccc.int|access-date=2017-09-27}}</ref> The [[global warming potential]] (compared to that of carbon dioxide) of many gases can be found in the IPCC 5th assessment report,<ref name="ipcc2013">Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang (2013) [http://www.climatechange2013.org/images/report/WG1AR5_Chapter08_FINAL.pdf "Anthropogenic and Natural Radiative Forcing"] (see Table 8.A.1). In: ''Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change''. Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.</ref> with an extract below for a few perfluoroalkanes.
{| class="wikitable"
|-
! Name !! Chemical formula !! Lifetime (y) !! GWP (100 years)
|-
| PFC-14 || {{chem2|CF4}} || 50000 || 6630
|-
| PFC-116 || {{chem2|C2F6}} || 10000 || 11100
|-
| PFC-c216 || {{chem2|c\-C3F6}} || 3000 || 9200
|-
| PFC-218 || {{chem2|C3F6}} || 2600 || 8900
|-
| PFC-318 || {{chem2|c\-C4F8}} || 3200 || 9540
|}

The aluminium smelting industry has been a major source of atmospheric perfluorocarbons ([[tetrafluoromethane]] and [[hexafluoroethane]] especially), produced as by-product of the electrolysis process.<ref>{{cite web|url=http://www.aluminum-production.com/anode_effect.html|title=The Anode Effect|website=aluminum-production.com|access-date=2014-05-20|archive-date=2019-02-22|archive-url= https://web.archive.org/web/20190222083751/http://www.aluminum-production.com/anode_effect.html |url-status=dead}}</ref> However, the industry has been actively involved in reducing emissions in recent years.<ref>{{cite web |url=http://www.climatevision.gov/sectors/aluminum/pdfs/tmsfirst.pdf |title=Perfluorocarbon (PFC) Generation at Primary Aluminum Smelters |access-date=|vauthors = Leber BP, etal|url-status=dead |archive-url=https://web.archive.org/web/20130216164759/http://www.climatevision.gov/sectors/aluminum/pdfs/tmsfirst.pdf |archive-date=2013-02-16 }} climatevision.gov</ref>

===Applications===
As they are inert, perfluoroalkanes have essentially no chemical uses, but their physical properties have led to their use in many diverse applications. These include:
*[[Perfluorocarbon tracer]]
*[[Liquid dielectric]]
*[[Chemical vapor deposition]]
*[[Organic Rankine cycle]]
*Fluorous biphasic catalysis<ref>{{cite web |url=https://chemistry.illinois.edu/system/files/inline-files/Flannigan.pdf |title=Fluorous Biphasic Catalysis |access-date= |first = David J. |last=Flannigan |date = 21 November 2002|website = chemistry.illinois.edu}}</ref>
*Cosmetics
*Ski waxes
As well as several medical uses:
*[[Contrast-enhanced ultrasound]]
*[[perfluorocarbon emulsions#Oxygen Therapeutics|Oxygen Therapeutics]]
*[[Blood substitute]]
*[[Liquid breathing]]
*Eye surgery <ref name=Imamura>{{cite journal
 |author1=Imamura Y|author2=Minami M|author3=Ueki M|author4=Satoh B|author5=Ikeda T|title=Use of perfluorocarbon liquid during vitrectomy for severe proliferative diabetic retinopathy
 |journal=Br J Ophthalmol |volume=87 |issue=5 |pages=563–566 |year=2003 |doi=10.1136/bjo.87.5.563|pmid=12714393|pmc=1771679}}</ref>
*Tattoo removal <ref>{{cite web |url=http://www.aslms.org/professional/documents/EditorsChoiceLSMFeb45.2.pdf |title=Archived copy |access-date=2014-05-19 |url-status=dead |archive-url=https://web.archive.org/web/20140519154936/http://www.aslms.org/professional/documents/EditorsChoiceLSMFeb45.2.pdf |archive-date=2014-05-19 }}</ref>

==Fluoroalkenes and fluoroalkynes==
[[Unsaturated compound|Unsaturated]] fluorocarbons are far more reactive than fluoroalkanes. Although [[difluoroacetylene]] is unstable (as is typical for related alkynes, see [[dichloroacetylene]]),<ref name=Lemal/> [[hexafluoro-2-butyne]] and related fluorinated alkynes are well known.
<gallery caption="Unsaturated fluorocarbons" widths="150px" heights="120px" perrow="5">
File:Perfluoroisobutene.svg|[[Perfluoroisobutene]], a reactive and highly toxic fluoroalkene gas
File:Tetrafluoroethylene.svg|[[Tetrafluoroethylene]], an important perfluorinated monomer.
File:Hexafluoropropylene.svg|[[Hexafluoropropylene]], another important perfluoroalkene.
File:Hexafluorobutyne.png|[[Hexafluoro-2-butyne]], a perfluoroalkyne.
</gallery>

===Polymerization===
Fluoroalkenes polymerize more exothermically than normal alkenes.<ref name=Lemal/> Unsaturated fluorocarbons have a driving force towards sp<sup>3</sup> hybridization due to the electronegative fluorine atoms seeking a greater share of bonding electrons with reduced s character in orbitals.<ref name=Lemal/> The most famous member of this class is [[tetrafluoroethylene]], which is used to manufacture [[polytetrafluoroethylene]] (PTFE), better known under the trade name [[Teflon]].

===Environmental and health concerns===
Fluoroalkenes and fluorinated alkynes are reactive and many are toxic for example [[perfluoroisobutene]].<ref>{{Cite web|title=Schedule 2 of Chemical Weapons Convention|url=https://www.opcw.org/chemical-weapons-convention/annexes/annex-chemicals/schedule-2|access-date=2022-01-25|website=OPCW|language=en}}</ref><ref name=Timp>{{cite book |doi=10.1016/B978-008043405-6/50040-2|chapter=Highly-toxic fluorine compounds|title=Fluorine Chemistry at the Millennium|year=2000|last1=Timperley|first1=Christopher M.|pages=499–538|isbn=9780080434056}}</ref> To produce [[polytetrafluoroethylene]] various [[fluorinated surfactant]]s are used, in the process known as [[Emulsion polymerization]], and the surfactant included in the polymer can bioaccumulate.

==Perfluoroaromatic compounds==
Perfluoroaromatic compounds contain only carbon and fluorine, like other fluorocarbons, but also contain an aromatic ring. The three most important examples are [[hexafluorobenzene]], [[Perfluorotoluene|octafluorotoluene]], and octafluoronaphthalene.
<gallery caption="Perfluoroaromatic compounds" widths="150px" heights="120px" perrow="5">
File:hexafluorobenzene.svg|[[Hexafluorobenzene]]
</gallery>

Perfluoroaromatic compounds can be manufactured via the Fowler process, like fluoroalkanes, but the conditions must be adjusted to prevent full fluorination. They can also be made by heating the corresponding perchloroaromatic compound with potassium fluoride at high temperature (typically 500&nbsp;°C), during which the chlorine atoms are replaced by fluorine atoms. A third route is defluorination of the fluoroalkane; for example, octafluorotoluene can be made from [[perfluoromethylcyclohexane]] by heating to 500&nbsp;°C with a nickel or iron catalyst.<ref>{{cite book |last=Banks|first=RE|date=1970|title=Fluorocarbons and their Derivatives, Second Edition|location=London|publisher=MacDonald & Co. (Publishers) Ltd.|pages=203–207|isbn=978-0-356-02798-2}}</ref>

Perfluoroaromatic compounds are relatively volatile for their molecular weight, with melting and boiling points similar to the corresponding aromatic compound, as the table below shows. They have high density and are non-flammable. For the most part, they are colorless liquids. Unlike the perfluoralkanes, they tend to be [[miscible]] with common solvents.{{citation needed|date=May 2017}}

{| class="wikitable"
|-
! Compound
! Melting point (°C)
! Boiling point (°C)
|-
| Hexafluorobenzene
| 5.3
| 80.5
|-
| [[Benzene]]
| 5.5
| 80.1
|-
|-
| Octafluorotoluene
| <−70
| 102–103
|-
| [[Toluene]]
| −95
| 110.6
|-
| Perfluoro(ethylbenzene)
|
| 114–115
|-
| [[Ethylbenzene]]
| −93.9
| 136.2
|-
| Octafluoronaphthalene
| 86–87
| 209<ref>{{cite web|url=http://www.chemspider.com/Chemical-Structure.60886.html|title=Octafluoronaphthalene|publisher=ChemSpider}}</ref>
|-
| [[Naphthalene]]
| 80.2
| 217.9
|}

==See also==
*[[:Category:Fluorocarbons]]
*[[Fluorochemical industry]]
*[[Hydrofluorocarbon]]
*[[Fluorographene]]
*[[Perfluorocycloalkene]] (PFCA)

==References==
{{Reflist|2}}

==External links==
{{Commons category|Perfluorocarbons}}
*[http://www.fluorocarbons.org Fluorocarbons and Sulphur Hexafluoride, proposed by the European Fluorocarbons Technical Committee]
*[http://www.vega.org.uk/video/programme/119 CFCs and Ozone Depletion] Freeview video provided by the Vega Science Trust.
*[https://web.archive.org/web/20070926183553/http://fluoroconsultants.com/db4/00322/fluoroconsultants.com/_download/INTRODUCTIONTOFLUOROPOLYMERS.pdf Introduction to fluoropolymers]
*[http://www.journals.royalsoc.ac.uk/content/9jcptv5dak4nafm2/fulltext.pdf Organofluorine chemistry by Graham Sandford]{{dead link|date=October 2017 |bot=InternetArchiveBot |fix-attempted=yes }}

{{Fluorine compounds}}

{{Authority control}}

[[Category:Fluorocarbons| ]]
[[Category:Greenhouse gases]]