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Perfluorosulfonic acids (PFSAs) are 
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s 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
Triflic acid, the short name for trifluoromethanesulfonic acid, TFMS, TFSA, HOTf or TfOH, is a sulfonic acid with the chemical formula CF3SO3H. It is one of the strongest known acids. Triflic acid is mainly used in research as a catalyst for es ...
. Perfluorosulfonic acids with six or more perfluorinated carbon atoms, i.e. from perfluorohexanesulfonic acid 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 thereforestrong acids
Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions ...
). Their perfluoroalkyl chain has a highly hydrophobic character.
Use
Perfluorooctanesulfonic acid
Perfluorooctanesulfonic acid (PFOS) (conjugate base perfluorooctanesulfonate) is a chemical compound having an eight-carbon fluorocarbon chain and a sulfonic acid functional group and thus a perfluorosulfonic acid. It is an anthropogenic (man-ma ...
, for example, has been used in hard chromium plating.
Regulation
Perfluorooctanesulfonic acid
Perfluorooctanesulfonic acid (PFOS) (conjugate base perfluorooctanesulfonate) is a chemical compound having an eight-carbon fluorocarbon chain and a sulfonic acid functional group and thus a perfluorosulfonic acid. It is an anthropogenic (man-ma ...
was included in Annex B of the Stockholm Convention
Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed on 22 May 2001 in Stockholm and effective from 17 May 2004, that aims to eliminate or restrict the production and use of persistent organic ...
in 2009 and subsequently in the EU POPs Regulation.
Perfluorohexanesulfonic acid including its salts and related compounds was proposed for inclusion in the Stockholm Convention.
Examples
Literature
* {{citation, editor-surname1=OECD
The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organisation with 38 member countries, founded in 1961 to stimulate e ...
, 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=en
References