Perfluorinated carboxylic acid
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.
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 + HF
- 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
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- "Water Pollution Continues At Famous Russian Lake". ScienceDaily. 25 March 2008. Retrieved 11 January 2009.
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