Perfluorinated carboxylic acids (PFCAs), or perfluorocarboxylic acids are compounds of the formula CnF(2n+1)CO2H. The simplest example is trifluoroacetic acid. These compounds are organofluorine analogues of ordinary carboxylic acids, but they are stronger by several pKa units and they exhibit great hydrophobic character. Perfluorinated dicarboxylic acids are also known, e.g. C2F4(CO2H)2.
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Applications and production
Trifluoroacetic acid is a widely employed acid, used for example in the synthesis of peptides. Its esters are useful in analytical chemistry. Longer chain perfluorinated carboxylic acids, e.g. with five to nine carbons, are useful fluorosurfactants and emulsifiers used in the production of Teflon and related fluoropolymers.
These compounds are typically prepared by electrochemical fluorination of the carboxylic acid fluorides followed by hydrolysis:
CnH(2n+1)COF + (2n+1) HF → CnF(2n+1)COF + (2n+1) H2 CnF(2n+1)COF + H2O → CnF(2n+1)CO2H + HFControversy
Larger PFCAs such as perfluorooctanoic acid (PFOA) are under scrutiny because they are bioaccumulative although it is unclear whether their presence poses a risk.