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]
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.
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]
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]
| 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 |