Perfluorinated compound

A perfluorinated compound (PFC) per- or polyfluoroalkyl chemical is an organofluorine compound containing only carbon-fluorine bonds (no C-H bonds) and C-C bonds but also other heteroatoms. PFCs have properties that represent a blend of fluorocarbons (containing only C-F and C-C bonds) and the parent functionalized organic species. For example, perfluorooctanoic acid functions as a carboxylic acid but with strongly altered surfactant and hydrophobic characteristics.[1] Fluorosurfactants are ubiquitously used in teflon, water resistant textiles and fire-fighting foam.

A perfluorinated compound (PFC) is an organofluorine compound containing only carbon-fluorine bonds, C-C bonds and other heteroatoms (no C-H bonds). PFCs have properties that result from the presence of fluorocarbons (containing only C-F and C-C bonds) and the functional group. Common functional groups in PFCs are OH, CO2H, chlorine, O, and SO3H.

Applications

Perfluorinated compounds are used ubiquitously: For example, fluorosurfactants are widely used in the production of teflon and related fluorinated polymers. They have been used to confer hydrophobicity, stain-resistance to fabrics and as fire-fighting foam.[2] Fluorosurfactants powerfully reduce surface tension by concentrating at the liquid-air interface due to the lipophobicity of fluorocarbons. Chlorofluorocarbons were formerly used as refrigerants until they were implicated in ozone degradation.

Production

Fluorine-containing compounds are derived from the mineral fluorspar, which is the chemical compound CaF2. There are examples of organisms that possess fluorine-containing compounds in their biochemistry and examples where organisms can be used to synthesize fluorinated compounds,[3] but the vast majority are man-made. The synthesis of perfluorinated compounds involves the use of F2 and HF reagents that are derived from natural product CaF2. A common industrial method for synthesizing perflurocompounds involves direct fluorination of organic compounds using F2 gas, where C-H bonds are replaced by C-F bonds accompanied by the formation of HF.[4]

Classes of PFCs by functional group

Representative members of this large family of compounds are listed below. Also numerous are compounds that contain many fluoride centers but also some hydrogen, e.g., trifluoroethanol.

Perfluorinated alkyl and aryl halides

Fluorochloroalkenes

Perfluoroethers and epoxides

Perfluoroalcohols

Primary and secondary perfluorinated alcohols are unstable with respect to dehydrofluorination.

Perfluoroamines

Perfluoroketones

Perfluorocarboxylic acids

Perfluoronitriles and isonitriles

  • Trifluoromethylisocyanide, the simplest perfluorinated isonitrile.
  • Trifluoromethylacetonitrile, the simplest perfluorinated nitrile

Perfluorinated aryl borates

Environmental and health concerns

There are several examples of environmental and health concerns around the industrial production and use of perfluoroalkane compounds. The unique chemical stability of perfluorinated compounds is desirable, and many times required, for many material applications but is also cause for environmental and health concerns.

Perfluoroalkanes

Low-boiling perfluoroalkanes are potent greenhouse gases, in part due to their very long atmospheric lifetime. The environmental concerns for perflurocompound's are similar to chlorofluorocarbons and other halogenated compounds used as refrigerants and fire suppression materials. The history of use, environmental impact, and recommendations for use are included in the Kyoto Protocol.

Fluorosurfactants

The fluorocarbons PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate) have both been investigated by the EU and the United States Environmental Protection Agency (EPA) which regards them being harmful to the environment.[5]

Fluorosurfactants tend to bioaccumulate, since they are extremely stable and can be stored in the bodies of humans and animals. Examples include PFOA and PFOS, frequently present in water resistant textiles and sprays conferring water resistant properties to textiles and fire-fighting foam.[5] Data from animal studies of PFOA indicate that it can cause several types of tumors and neonatal death and may have toxic effects on the immune, liver, and endocrine systems. As of 2010 data on the human health effects of PFOA were sparse.[6]

As of 2015, the U.S. Air Force had been testing 82 former and active US military installations for fluorosurfactants contained in fire fighting foam.[7] In 2015, PFCs were found in groundwater at Naval Air Station Brunswick, Maine and Grissom Air Reserve Base, Indiana, and in well water at Pease Air Force Base, New Hampshire, where 500 people including children had blood tests as part of a bio-monitoring plan through the state Department of Health and Human Services. The U.S. Department of Defense's research programs have been trying to define nature and extent of PFAS contamination at U.S. military sites, especially in groundwater.[8]

A 2018 report to Congress indicated that "at least 126 drinking water systems on or near military bases" were contaminated with PFAS compounds.[9][10]

A 2016 study found unsafe[11] levels of fluorosurfactants in 194 out of 4,864 water supplies in 33 U.S. states. Covering two-thirds of drinking water supplies in the United States, the study found thirteen states accounted for 75% of the detections. In order of frequency, these were: California, New Jersey, North Carolina, Alabama, Florida, Pennsylvania, Ohio, New York, Georgia, Minnesota, Arizona, Massachusetts, and Illinois. Firefighting foam was singled out as a major contributor.[12]

See also

References

  1. ↑ 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
  2. ↑ Sedlak, Meg (October 2016). "Profile - Perfluorooctane Sulfonate (PFOS)" (PDF). sfei.org. San Francisco Estuary Institute. Retrieved 2 November 2016.
  3. ↑ Murphy CD, Schaffrath C, O'Hagan D.: "Fluorinated natural products: the biosynthesis of fluoroacetate and 4-fluorothreonine in Streptomyces cattleya" Chemosphere. 2003 Jul;52(2):455-61.
  4. ↑ Lagow, Richard J.; Margrave, John L. (2007-03-09), "Direct Fluorination: A "New" Approach to Fluorine Chemistry", Progress in Inorganic Chemistry, John Wiley & Sons, Inc., pp. 161–210, doi:10.1002/9780470166277.ch3, ISBN 9780470166277
  5. 1 2 US Environmental Protection Agency. "FAQ". Perfluorooctanoic Acid (PFOA) and Fluorinated Telomers. Retrieved 11 May 2011.
  6. ↑ Steenland, Kyle; Fletcher, Tony; Savitz, David A. (2010). "Epidemiologic Evidence on the Health Effects of Perfluorooctanoic Acid (PFOA)". Environmental Health Perspectives. 118 (8): 1100–8. doi:10.1289/ehp.0901827. PMC 2920088. PMID 20423814.
  7. ↑ Associated Press (19 September 2015). "Grissom officials: Well tests show no chemical pollution". LIN Television Corporation. Retrieved 19 September 2015.
  8. ↑ Strategic Environmental Research and Development Program (SERDP), Environmental Security Technology Certification Program (ESTCP) Per- and Polyfluoroalkyl Substances (PFASs): Analytical and Characterization Frontiers webinarslides, January 28, 2016
  9. ↑ Lustgarten, Abrahm (2018-06-20). "Suppressed Study: The EPA Underestimated Dangers of Widespread Chemicals". ProPublica. Lisa Song,Talia Buford. Retrieved 2018-06-23.
  10. ↑ Associated Press (2017-07-31). "Air Force won't pay for towns' water contamination costs". Air Force Times. Retrieved 2018-06-23.
  11. ↑ Above the minimum reporting levels required by the EPA − 70 parts per trillion (ng/L) for PFOS and PFOA
  12. ↑ Unsafe levels of toxic chemicals found in drinking water for 6 million Americans Science X network, phys.org, August 9, 2016
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