Perfluoroalkyl carboxylic acids

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. The simplest example is trifluoroacetic acid. These compounds are organofluorine analogues of ordinary carboxylic acids, but they are stronger by several pK_a units and they exhibit great hydrophobic character. Perfluoroalkyl dicarboxylic acids (PFdiCAs) are also known, e.g. C₂F₄(CO₂H)₂.^[1]

Thumb — Perfluorononanoic acid, an example of a perfluoroalkyl carboxylic acid (PFCA)

Remove ads

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 being under scrutiny because they are extremely persistent and bioaccumulative. Short-chain PFCAs (scPFCAs) are formed from atmospheric oxidation of fluorotelomer compounds and chlorofluorocarbon (CFC) replacements introduced as a result of the Montreal Protocol.^[2]^[3]

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.^[4]^[5]^[6]

Remove ads

More information Name, Abbreviation ...

Name	Abbreviation	Molecular formula	Molecular weight (g/mol)	CAS No.
Trifluoroacetic acid	TFA	CF₃COOH	114.02	76-05-1
Perfluoropropanoic acid	PFPrA	C₂F₅COOH	164.03	422-64-0
Perfluorobutanoic acid	PFBA	C₃F₇COOH	214.04	375-22-4
Perfluoropentanoic acid [de]	PFPeA	C₄F₉COOH	264.05	2706-90-3
Perfluorohexanoic acid	PFHxA	C₅F₁₁COOH	314.05	307-24-4
Perfluoroheptanoic acid [de]	PFHpA	C₆F₁₃COOH	364.06	375-85-9
Perfluorooctanoic acid	PFOA	C₇F₁₅COOH	414.07	335-67-1
Perfluorononanoic acid	PFNA	C₈F₁₇COOH	464.08	375-95-1
Perfluorodecanoic acid	PFDA	C₉F₁₉COOH	514.08	335-76-2
Perfluoroundecanoic acid [de]	PFUnDA	C₁₀F₂₁COOH	564.09	2058-94-8
Perfluorododecanoic acid [de]	PFDoDA	C₁₁F₂₃COOH	614.10	307-55-1
Perfluorotridecanoic acid [de]	PFTrDA	C₁₂F₂₅COOH	664.10	72629-94-8
Perfluorotetradecanoic acid [de]	PFTeDA	C₁₃F₂₇COOH	714.11	376-06-7

Close

Remove ads

[1]
Siegemund G, Schwertfeger W, Feiring A, Smart B, Behr F, Vogel H, McKusick B (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH: a11_349. doi:10.1002/14356007.a11_349. ISBN 978-3-527-30673-2.
[2]
McGrath M (14 May 2020). "Ozone layer: Concern grows over threat from replacement chemicals". BBC News. Retrieved 23 May 2024.
[3]
Pickard HM, Criscitiello AS, Persaud D, Spencer C, Muir DC, Lehnherr I, et al. (28 May 2020). "Ice Core Record of Persistent Short‐Chain Fluorinated Alkyl Acids: Evidence of the Impact From Global Environmental Regulations". Geophysical Research Letters. 47 (10). doi:10.1029/2020GL087535.
[4]
Synthesis Report on Understanding Side-Chain Fluorinated Polymers and Their Life Cycle (PDF). OECD Series on Risk Management. Vol. 73. Environment, Health and Safety, Environment Directorate, OECD. 2022.
[5]
Letcher RJ, Chu S, Smyth SA (April 2020). "Side-chain fluorinated polymer surfactants in biosolids from wastewater treatment plants". Journal of Hazardous Materials. 388: 122044. doi:10.1016/j.jhazmat.2020.122044. PMID 31955025. S2CID 210830499.
[6]
Brendel S, Fetter É, Staude C, Vierke L, Biegel-Engler A (2018-02-27). "Short-chain perfluoroalkyl acids: environmental concerns and a regulatory strategy under REACH". Environmental Sciences Europe. 30 (1): 9. doi:10.1186/s12302-018-0134-4. PMC 5834591. PMID 29527446.

Remove ads

"Chapter 2: Perfluoroalkyl carboxylic (a) and dicarboxylic (b) acids". Fact Cards of Major Groups of Per- and Polyfluoroalkyl Substances (PFASs). OECD Environment, Health and Safety Publications Series on Risk Management. Vol. 68. The Organisation for Economic Co-operation and Development (OECD). January 2022. pp. 16–32.
Guo Z, Liu X, Krebs KA, Roache NF (March 2009). "Perfluorocarboxylic acid content in 116 articles of commerce". Research Triangle Park, NC: US Environmental Protection Agency.

Remove ads

[Ullmann-1] [1]
Siegemund G, Schwertfeger W, Feiring A, Smart B, Behr F, Vogel H, McKusick B (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH: a11_349. doi:10.1002/14356007.a11_349. ISBN 978-3-527-30673-2.

[2] [2]
McGrath M (14 May 2020). "Ozone layer: Concern grows over threat from replacement chemicals". BBC News. Retrieved 23 May 2024.

[3] [3]
Pickard HM, Criscitiello AS, Persaud D, Spencer C, Muir DC, Lehnherr I, et al. (28 May 2020). "Ice Core Record of Persistent Short‐Chain Fluorinated Alkyl Acids: Evidence of the Impact From Global Environmental Regulations". Geophysical Research Letters. 47 (10). doi:10.1029/2020GL087535.

[4] [4]
Synthesis Report on Understanding Side-Chain Fluorinated Polymers and Their Life Cycle (PDF). OECD Series on Risk Management. Vol. 73. Environment, Health and Safety, Environment Directorate, OECD. 2022.

[5] [5]
Letcher RJ, Chu S, Smyth SA (April 2020). "Side-chain fluorinated polymer surfactants in biosolids from wastewater treatment plants". Journal of Hazardous Materials. 388: 122044. doi:10.1016/j.jhazmat.2020.122044. PMID 31955025. S2CID 210830499.

[6] [6]
Brendel S, Fetter É, Staude C, Vierke L, Biegel-Engler A (2018-02-27). "Short-chain perfluoroalkyl acids: environmental concerns and a regulatory strategy under REACH". Environmental Sciences Europe. 30 (1): 9. doi:10.1186/s12302-018-0134-4. PMC 5834591. PMID 29527446.

[1]

[2]

[3]

[4]

[5]

[6]

Perfluoroalkyl carboxylic acids

Wikiwand in your browser!

Applications

Production

Environmental concerns

Common examples

See also

References

Further reading