Perfluorocarboxylic acids

Perfluorobutanoic acid
C ₃ F ₇ COOH

Perfluorooctanoic acid
C ₇ F ₁₇ COOH

Perfluorocarboxylic acids ( PFCA from English perfluorocarboxylic acid ) are chemical compounds of the formula C _n F _{(2n + 1)} COOH and thus belong to the family of perfluorinated and polyfluorinated alkyl compounds (PFAS). The simplest example of a perfluorocarboxylic acid is trifluoroacetic acid . PFCA with seven or more perfluorinated carbon atoms , i.e. from perfluorooctanoic acid , are referred to as long-chain.

Perfluorodicarboxylic acids are also known, e.g. B. Dodecafluorooctanedioic acid [C ₈ F ₁₂ (COOH)] ₂ .

production

These compounds can be produced by electrochemical fluorination of the carboxylic acid fluorides and subsequent hydrolysis :

C _n H _{(2n + 1)} COF + (2n + 1) HF → C _n F _{(2n + 1)} COF + (2n + 1) H ₂

C _n F _{(2n + 1)} COF + H ₂ O → C _n F _{(2n + 1)} CO ₂ H + HF

Alternatively, it is produced by means of fluorotelomerization .

properties

Perfluorocarboxylic acids are organofluoro analogs of common carboxylic acids , but they are several p K _S units stronger (and are therefore strong acids) and have a large hydrophobic character.

use

Trifluoroacetic acid is a widely used acid that is used, for example, in the synthesis of peptides . Esters of trifluoroacetic acid are useful in analytical chemistry. Perfluorinated carboxylic acids with e.g. Five to nine carbon atoms are useful fluorosurfactants and emulsifiers that have been used in the manufacture of polytetrafluoroethylene and related fluoropolymers.

regulation

In the EU, perfluorooctanoic acid (PFOA), perfluorononanoic acid , perfluorodecanoic acid , perfluorundecanoic acid , perfluorododecanoic acid , perfluorotridecanoic acid and perfluorotetradecanoic acid were rated as SVHC substances. As of July 4, 2020, PFOA may no longer be manufactured or marketed in the EU. In mixtures, the upper limit for PFOA is 25 ppb and for PFOA precursors is 1000 ppb.

PFOA including its salts and related compounds have been proposed for inclusion in the Stockholm Convention .

Individual evidence

1. ↑ Amélie Ritscher et al .: Zurich Statement on Future Actions on Per- and Polyfluoroalkyl Substances (PFASs). In: Environmental Health Perspectives . 126, 2018, doi: 10.1289 / ehp.1509934 .
2. ↑ External identifiers or database links for dodecafluorooctanedioic acid : CAS number: 678-45-5, EC number: 670-455-3, ECHA InfoCard: 100.196.176 , PubChem : 2733268 , ChemSpider : 2015071 , Wikidata : Q72500641 .
3. ^ ^{A b} Günter Siegemund, Werner Schwertfeger, Andrew Feiring, Bruce Smart, Fred Behr, Herward Vogel, Blaine McKusick: Fluorine Compounds, Organic . Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi : 10.1002 / 14356007.a11_349 .
4. ↑ ECHA - Candidate List of Substances of Very High Concern for Authorization , accessed on September 23, 2018.
5. ↑ Regulation (EU) 2017/1000 of the Commission of 13 June 2017 amending Annex XVII of Regulation (EC) No. 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) Perfluorooctanoic acid (PFOA), its salts and PFOA precursor compounds
6. ^ Chemicals proposed for listing under the Convention . In: chm.pops.int , accessed on September 23, 2018.