Hydrofluorocarbons (HFCs) are synthetic organic compounds that contain fluorine and hydrogen atoms, and are the most common type oforganofluorine compounds. Most are gases at room temperature and pressure. They are frequently used inair conditioning and asrefrigerants;R-134a (1,1,1,2-tetrafluoroethane) is one of the most commonly usedHFCrefrigerants. In order to aid the recovery of thestratospheric ozone layer, HFCs were adopted to replace the more potentchlorofluorocarbons (CFCs) such asR-12, which were phased out from use by theMontreal Protocol, andhydrochlorofluorocarbons (HCFCs) such asR-21 which are presently being phased out.[1][2] HFCs are also used in insulating foams, aerosol propellants, as solvents and for fire protection.
HFCs may not harm the ozone layer as much as the compounds they replace, but they still contribute toglobal warming – with some liketrifluoromethane (CHF3 or R-23) having 11,700 times the warming potential of carbon dioxide.[3] HFC atmospheric concentrations and contribution toanthropogenicgreenhouse gas emissions are rapidly increasing – consumption rose from near zero in 1990 to 1.2 billion tons of carbon dioxide equivalent in 2010[4] – causing international concern about theirradiative forcing.
Fluorocarbons with fewC–Fbonds behave similarly to the parenthydrocarbons, but their reactivity can be altered significantly. For example, bothuracil and5-fluorouracil are colourless, high-melting crystalline solids, but the latter is a potent anti-cancer drug. The use of the C–F bond in pharmaceuticals is predicated on this altered reactivity.[5] Several drugs andagrochemicals contain only one fluorine center or onetrifluoromethyl group.
Unlike other greenhouse gases in theParis Agreement, hydrofluorocarbons are included in other international negotiations.[6]
In September 2016, theNew York Declaration on Forests urged a global reduction in the use of HFCs.[7] On 15 October 2016, due to these chemicals' contribution toclimate change, negotiators from 197 nations meeting at a summit of theUnited Nations Environment Programme in Kigali, Rwanda reached a legally-binding accord (theKigali Amendment) to phase down hydrofluorocarbons (HFCs) in an amendment to theMontreal Protocol.[8][9][10] As of February 2020, 16 U.S. states ban or are phasing down HFCs.[11]
COVID-19 relief legislation, which included a measure that would require chemical manufacturers to phase down the production and use of HFCs, was passed by theUnited States House of Representatives andUnited States Senate on December 21, 2020.[12] The U.S. Environmental Protection Agency signed a final rule phasing down HFCs on 23 September 2021.[13]
{{cite journal}}:Cite journal requires|journal= (help){{citation}}: CS1 maint: work parameter with ISBN (link)