Perfluoroalkyl carboxylic acids (PFCAs), or perfluorocarboxylic acids are compounds of the formula C_nF_(2n+1)CO₂H that belong to the class of

per- and polyfluoroalkyl substances Per- and polyfluoroalkyl substances (also PFAS, PFASs, and informally referred to as "forever chemicals") are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain; there are 7 milli ...

. The simplest example is

trifluoroacetic acid Trifluoroacetic acid (TFA) is a synthetic organofluorine compound with the chemical formula CF3CO2H. It belongs to the subclass of per- and polyfluoroalkyl substances (PFASs) known as ultrashort-chain perfluoroalkyl acids (PFAAs). TFA is not ...

. These compounds are organofluorine analogues of ordinary

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s, but they are stronger by several pK_a units and they exhibit great

hydrophobic In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

character. Perfluoroalkyl dicarboxylic acids (PFdiCAs) are also known, e.g. C₂F₄(CO₂H)₂.

Applications

Trifluoroacetic acid Trifluoroacetic acid (TFA) is a synthetic organofluorine compound with the chemical formula CF3CO2H. It belongs to the subclass of per- and polyfluoroalkyl substances (PFASs) known as ultrashort-chain perfluoroalkyl acids (PFAAs). TFA is not ...

is a widely employed acid, used for example in the synthesis of

peptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

s. Its esters are useful in analytical chemistry. Longer-chain perfluoroalkyl carboxylic acids, e.g. with five to nine carbons, are useful

fluorosurfactant Per- and polyfluoroalkyl substances (also PFAS, PFASs, and informally referred to as "forever chemicals") are a group of synthetic Organofluorine chemistry, organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl ...

s and emulsifiers used in the production of

polytetrafluoroethylene Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a corporate spin-of ...

(Teflon) and related

fluoropolymer A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon, ...

Production

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

Environmental concerns

Long-chain PFCAs such as

perfluorooctanoic acid Perfluorooctanoic acid (PFOA; conjugate acid, conjugate base perfluorooctanoate; also known colloquially as C8, from its chemical formula C8HF15O2) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in ch ...

(PFOA) are either banned or being under scrutiny because they are extremely persistent and

bioaccumulative Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. ...

. Short-chain PFCAs (scPFCAs) are formed from atmospheric oxidation of fluorotelomer compounds and

chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly Halogenation, halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). They are produced as volatility (chemistry), volat ...

(CFC) replacements introduced as a result of the

Montreal Protocol The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 ...

. Side-chain fluorinated polymers (SCFPs), in which fluorotelomers are attached to a polymer backbone, may release fluorotelomer alcohols through

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

. The latter are then degraded to PFCAs. Urethane SCFP hydrolysis simplified

Applications

Production

Environmental concerns

Common examples

See also

References

Further reading