Perfluorosulfonic acids

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, i.e. from perfluorohexanesulfonic acid onwards, are referred to as long-chain.[1]

Perfluorooctanesulfonic acid Trifluoromethanesulfonic acid

## Properties

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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

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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

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

Perfluorohexanesulfonic acid was included in Annex B of the Stockholm Convention in 2022.[4]

## Examples

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Name  | Abbreviation  | Structural formula | Molecular weight (g/mol)  | CAS No.

|
|
|
|

Perfluoropropanesulfonic acid | PFPrS  | C3F7SO3H  | 250.09  | 423-41-6
Perfluorobutanesulfonic acid | PFBS  | C4F9SO3H  | 300.10  | 375-73-5
Perfluoropentanesulfonic acid | PFPS  | C5F11SO3H  | 350.11  | 2706-91-4
Perfluorohexanesulfonic acid | PFHxS  | C6F13SO3H  | 400.12  | 355-46-4
Perfluoroheptanesulfonic acid | PFHpS  | C7F15SO3H  | 450.12  | 375-92-8
Perfluorooctanesulfonic acid | PFOS  | C8F17SO3H  | 500.13  | 1763-23-1
Perfluorononanesulfonic acid | PFNS  | C9F19SO3H  | 550.14  | 68259-12-1
Perfluorodecanesulfonic acid | PFDS  | C10F21SO3H  | 600.15  | 335-77-3

## See also

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* Perfluoro(4-ethylcyclohexane)sulfonic acid, a cyclic analogue

## Literature

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* OECD, ed. (2022), "3. Perfluoroalkane sulfonic (a) and sulfinic (b) acids", Fact Cards of Major Groups of Per- and Polyfluoroalkyl Substances (PFASs), OECD Environment, Health and Safety Publications 68 Series on Risk Management, pp. 31–41

## References

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1. ^ "Terminology | FluoroCouncil".
2. ^ Bohannon, Meredith E; Narizzano, Allison M; Guigni, Blas A; East, Andrew G; Quinn, Michael J (2023). "Next-generation PFAS 6:2 fluorotelomer sulfonate reduces plaque formation in exposed white-footed mice". Toxicological Sciences. 192 (1): 97–105\. doi:10.1093/toxsci/kfad006.97-105&rft.date=2023&rft_id=info:doi/10.1093/toxsci/kfad006&rft.aulast=Bohannon&rft.aufirst=Meredith+E&rft.au=Narizzano,+Allison+M&rft.au=Guigni,+Blas+A&rft.au=East,+Andrew+G&rft.au=Quinn,+Michael+J&rfr_id=info:sid/en.wikipedia.org:Perfluorosulfonic+acids" class="Z3988">
3. ^ Regulation (EU) 2019/1021 of the European Parliament and of the Council of 20 June 2019 on persistent organic pollutants
4. ^ "UN experts recommend elimination of additional hazardous chemicals to protect human health and the environment".