Perfluorosulfonic acids

Perfluorosulfonic acids (PFSAs) are chemical compounds of the formula C_nF_(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, i.e. from perfluorohexanesulfonic acid onwards, are referred to as long-chain.^[1]

Perfluorooctanesulfonic acid

Trifluoromethanesulfonic acid

Properties

Perfluorosulfonic acids are organofluoroanalogues of conventional alkanesulfonic acids, but they are several pK_A 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. Since the early 2000's 6:2-Fluorotelomersulfonic acid has been used as a replacement for Perfluorooctanesulfonic acid.^[2]

Regulation

Perfluorooctanesulfonic acid was included in Annex B of the Stockholm Convention in 2009 and subsequently in the EU POPs Regulation.^[3]

Perfluorohexanesulfonic acid including its salts and related compounds was proposed for inclusion in the Stockholm Convention.^[4]

Examples

Literature

• "3. Perfluoroalkane sulfonic (a) and sulfinic (b) acids" (in English), Fact Cards of Major Groups of Per- and Polyfluoroalkyl Substances (PFASs), OECD Environment, Health and Safety Publications 68 Series on Risk Management, 2022, pp. 31–41, https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/cbc/mono(2022)1&doclanguage=en 

References

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