Perfluoroalkyl carboxylic acids

Trifluoroacetic acid is a widely employed acid, used for example in the synthesis of peptides. Its esters are useful in analytical chemistry.

Longer-chain perfluoroalkyl carboxylic acids, e.g. with five to nine carbons, are useful fluorosurfactants and emulsifiers used in the production of polytetrafluoroethylene (Teflon) and related fluoropolymers.^[1]

These compounds are typically prepared by electrochemical fluorination of the carboxylic acid fluorides followed by hydrolysis:

C_nH_(2n+1)COF + (2n+1) HF → C_nF_(2n+1)COF + (2n+1) H₂

C_nF_(2n+1)COF + H₂O → C_nF_(2n+1)CO₂H + HF

Long-chain PFCAs such as perfluorooctanoic acid (PFOA) are either banned or under scrutiny because they are extremely persistent and bioaccumulative. In 2019, PFOA, its salts, and PFOA-related compounds were added to Annex A of the Stockholm Convention on Persistent Organic Pollutants,^[2] requiring treaty members to take measures to eliminate their production and use. In 2025, C₉–C₂₁ long-chain PFCAs (C_nF_2n+1COOH, 8 ≤ n ≤ 20), their salts, and related compounds were added to Annex A.^[3][4]

Short-chain PFCAs (scPFCAs) are formed from atmospheric oxidation of fluorotelomer compounds and chlorofluorocarbon (CFC) replacements introduced as a result of the Montreal Protocol.^[5][6]

Side-chain fluorinated polymers (SCFPs), in which fluorotelomers are attached to a polymer backbone, may release fluorotelomer alcohols through hydrolysis. The latter are then degraded to PFCAs.^[7][8][9]

• Per- and polyfluoroalkyl substances
• Surflon S-111