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Perfluorosulfonic acids (PFSAs) are chemical compounds of the formula CnF(2n+1)SO3H and thus belong to the family of perfluorinated and polyfluorinated alkyl compounds (PFASs). The simplest example of a perfluorosulfonic acid is the trifluoromethanesulfonic acid. Perfluorosulfonic acids with six or more perfluorinated 
carbon atoms
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up o ...
, i.e. from perfluorohexanesulfonic acid
Perfluorohexanesulfonic acid (PFHxS) (conjugate base perfluorohexanesulfonate) is a synthetic chemical compound. It is one of many compounds collectively known as per- and polyfluoroalkyl substances (PFASs). It is an anionic fluorosurfactant and a ...
onwards, are referred to as long-chain.
Properties
Perfluorosulfonic acids are organofluoroanalogues of conventional alkanesulfonic acids, but they are several pKA units stronger (and are therefore strong acids). Their perfluoroalkyl chain has a highly hydrophobic character.Use
Perfluorooctanesulfonic acid, for example, has been used in hard chromium plating.Regulation
Perfluorooctanesulfonic acid was included in Annex B of the Stockholm Convention in 2009 and subsequently in the EU POPs Regulation.Perfluorohexanesulfonic acid
Perfluorohexanesulfonic acid (PFHxS) (conjugate base perfluorohexanesulfonate) is a synthetic chemical compound. It is one of many compounds collectively known as per- and polyfluoroalkyl substances (PFASs). It is an anionic fluorosurfactant and a ...
including its salts and related compounds was proposed for inclusion in the Stockholm Convention.
Examples
Literature
* {{citation, editor-surname1= OECD, title=Fact Cards of Major Groups of Per- and Polyfluoroalkyl Substances (PFASs), series=OECD Environment, Health and Safety Publications 68 Series on Risk Management, issue=ENV/CBC/MONO(2022)1, at=pp. 31–41, contribution=3. Perfluoroalkane sulfonic (a) and sulfinic (b) acids, date=2022, language=English, url=https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/cbc/mono(2022)1&doclanguage=enReferences