From Wikipedia, the free encyclopedia
  (Redirected from Chlorofluoroalkane)
Jump to: navigation, search
"HCFC" redirects here. For Hull City Association Football Club, see Hull City A.F.C..

A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. The manufacture of such compounds has been phased out under the Montreal Protocol, and are being replaced with products such as HFCs (e.g., R-410A), hydrocarbons, and CO2, because CFCs contribute to ozone depletion in the upper atmosphere.

Structure, properties and production[edit]

As in simpler alkanes, carbon in the CFCs and the HCFCs is tetrahedral. Since the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry.[1]




HCCl3 + 2 HF → HCF2Cl + 2 HCl


CF3CH2Cl + Br2 → CF3CHBrCl + HBr



CCl3F → CCl2F. + Cl.




Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the monomer that is converted into Teflon.[2]

Classes of compounds, nomenclature[edit]

  • Hydrochlorofluorocarbons (HCFCs): when derived from methane and ethane these compounds have the formulae CClmFnH4-m-n and C2ClxFyH6-x-y, where m, n, x, and y are nonzero.
  • Bromochlorofluorocarbons and bromofluorocarbons have formulae similar to the CFCs and HCFCs but also include bromine.

Numbering system[edit]



Freons containing bromine is signified by four numbers. Isomers, which are common for ethane and propane derivatives, are indicated by letters following the numbers.

Principal CFCs
Systematic name Common/trivial
name(s), code
Boiling point (°C) Formula
Chlorodifluoromethane-Pentafluoromethane R-410A, Puron, AZ-20 -48.5 50% CH2F2/50% CHF2CF3
Chlorodifluoromethane R-22, HCFC-22 −40.8 CHClF2
Dichlorofluoromethane R-21, HCFC-21 8.9 CHCl2F
Bromochlorodifluoromethane BCF, Halon 1211, H-1211, Freon 12B1 -3.7 CBrClF2
1-Bromo-2-chloro-1,1,2-trifluoroethane Halon 2311a 51.7 CHClFCBrF2
2-Bromo-2-chloro-1,1,1-trifluoroethane Halon 2311 50.2 CF3CHBrCl





Commercial development and use[edit]








Ozone-depleting gas trends



Regulatory gap[edit]

While the production and consumption of CFCs are regulated under the Montreal Protocol, emissions from existing banks of CFCs are not regulated under the agreement. In 2002, there were an estimated 5,791 kilotons of CFCs in existing products such as refrigerators, air conditioners, aerosol cans and others.[7] Approximately one-third of these CFCs are projected to be emitted over the next decade if action is not taken, posing a threat to both the ozone layer and the climate.[8] A proportion of these CFCs can be safely captured and destroyed.

Regulation and DuPont[edit]


Phasing-out of CFCs[edit]




The interim replacements for CFCs are hydrochlorofluorocarbons (HCFCs), which deplete stratospheric ozone, but to a much lesser extent than CFCs.[11] Ultimately, hydrofluorocarbons (HFCs) will replace HCFCs. Unlike CFCs and HCFCs, HFCs have an ozone depletion potential (ODP) of 0. DuPont began producing hydrofluorocarbons as alternatives to Freon in the 1980s. These included Suva refrigerants and Dymel propellants.[12] Natural refrigerants are climate friendly solutions that are enjoying increasing support from large companies and governments interested in reducing global warming emissions from refrigeration and air conditioning. Hydrofluorocarbons are included in the Kyoto Protocol because of their very high Global Warming Potential and are facing calls to be regulated under the Montreal Protocol[dubious ][13] due to the recognition of halocarbon contributions to climate change.[14]


Development of alternatives for CFCs[edit]



One of the natural refrigerants (along with Ammonia and Carbon Dioxide), hydrocarbons have negligible environmental impacts and are also used worldwide in domestic and commercial refrigeration applications, and are becoming available in new split system air conditioners.[16] Various other solvents and methods have replaced the use of CFCs in laboratory analytics.[17]

Applications and replacements for CFCs
Application Previously used CFC Replacement

Environmental impacts[edit]


Infrared absorption bands trap heat from escaping earth's atmosphere. In the case of CFCs, the strongest of these bands are located in the spectral region 7.8–15.3 µm [18] – referred to as an atmospheric window due to the relative transparency of the atmosphere within this region.[19] The strength of CFC bands and the unique susceptibility of the atmosphere, at which the compound absorbs and emits radiation, are two factors that contribute to CFCs' "super" greenhouse effect.[20] Another such factor is the low concentration of the compound. Because CO2 is close to saturation with high concentrations,[clarification needed] it takes more of the substance to enhance the greenhouse effect. Conversely, the low concentration of CFCs allow their effects to increase linearly with mass.[20]

Tracer of ocean circulation[edit]

Since the time history of CFC concentrations in the atmosphere is relatively well known, they have provided an important constraint on ocean circulation. CFCs dissolve in seawater at the ocean surface and are subsequently transported into the ocean interior. Since CFCs are conservative, their concentration in the ocean interior reflects simply the convolution of their atmospheric time evolution and ocean circulation and mixing.


Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents.[21] The entry of CFCs into the ocean makes them extremely useful as transient tracers to estimate rates and pathways of ocean circulation and mixing processes.[22] However, due to production restrictions of CFCs in the 1980s, atmospheric concentrations of CFC-11 and CFC-12 has stopped increasing, and the CFC-11 to CFC-12 ratio in the atmosphere have been steadily decreasing, making water dating of water masses more problematic.[22] Incidentally, production and release of sulfur hexafluoride (SF6) have rapidly increased in the atmosphere since the 1970s.[22] Similar to CFCs, SF6 is also an inert gas and is not affected by oceanic chemical or biological activities.[23] Thus, using CFCs in concert with SF6 as a tracer resolves the water dating issues due to decreased CFC concentrations.


Partial pressure and ratio dating techniques[edit]


pCFC = [CFC]/F(T,S)

where [CFC] is the measured CFC concentration (pmol kg-1) and F is the solubility of CFC gas in seawater as a function of temperature and salinity.[25] The CFC partial pressure is expressed in units of 10-12 atmospheres or parts-per-trillion (ppt).[26] The solubility measurements of CFC-11 and CFC-12 have been previously measured by Warner and Weiss[26] Additionally, the solubility measurement of CFC-113 was measured by Bu and Warner[27] and SF6 by Wanninkhof et al.[28] and Bullister et al.[29] Theses authors mentioned above have expressed the solubility, F, at a total pressure of 1 atm as:


where F = solubility expressed in either mol l-1 or mol kg-1 atm-1 T = absolute temperature S = salinity in parts per thousand (ppt) a1, a2, a3, b1, b2, and b3 are constants to be determined from the least squares fit to the solubility measurements.[27] This equation is derived from the integrated Van 't Hoff equation and the logarithmic Setchenow salinity dependence.[27]


Once the partial pressure of the CFC (or SF6) is derived, it is then compared to the atmospheric time histories for CFC-11, CFC-12, or SF6 in which the pCFC directly corresponds to the year with the same measurement. The difference between the corresponding date and the collection date of the seawater sample is the average age for the water parcel.[24] The age of a parcel of water can also be calculated using the ratio of two CFC partial pressures or the ratio of the SF6 partial pressure to a CFC partial pressure.[24]


According to their material safety data sheets, CFCs and HCFCs are colourless, volatile, toxic liquids and gases with a faintly sweet ethereal odour. Overexposure at concentrations of 11% or more may cause dizziness, loss of concentration, central nervous system depression and/or cardiac arrhythmia. Vapors displace air and can cause asphyxiation in confined spaces. Although non-flammable, their combustion products include hydrofluoric acid, and related species.[30] It is important to note that normal occupational exposure is rated at 0.07% and does not pose any serious health risks.[31]


  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
  3. ^ Inventors accessed December 21, 2007
  5. ^ McNeill, J. R. Something New Under the Sun: An Environmental History of the Twentieth-Century World (2001) New York: Norton, xxvi, 421 pp. (as reviewed in the Journal of Political Ecology)
  6. ^ "Illegal Trade in Ozone Depleting Substances" United Nations Environmental Programme, 2007. Web. 3 Apr. 2011.
  7. ^ IPCC/TEAP Special Report on Ozone and Climate
  8. ^ Chlorofluorocarbons: An Overlooked Climate Threat, EESI Congressional Briefing. Retrieved on 2011-09-24.
  10. ^ Welcome to the Halon Corporation. Retrieved on 2011-09-24.
  11. ^ "Ozone Layer Depletion", U.S. Environmental Protection Agency accessed June 25, 2008
  12. ^ Freon® : 1930. In Depth. (2009-01-30). Retrieved on 2011-09-24.
  13. ^ John M. Broder (November 9, 2010). "A Novel Tactic in Climate Fight Gains Some Traction". The New York Times. p. A9. Retrieved 2013-02-05. 
  14. ^ Velders et al., PNAS March 20, 2007 vol. 104 no. 12 4814–4819 [1] "The importance of the Montreal Protocol in protecting climate"
  15. ^ HCFC Phaseout Schedule. (2006-06-28). Retrieved on 2011-09-24.
  16. ^ "Greenpeace, Cool Technologies". (PDF). Retrieved on 2011-09-24.
  17. ^ Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003. (2003-01-01). Retrieved on 2011-09-24.
  18. ^ Rothman, L (2009). "The HITRAN 2008 molecular spectroscopic database". Journal of Quantitative Spectroscopy and Radiative Transfer. 100pages=533-572. 
  19. ^ Ramanathan, V (1975). "Greenhouse Effect Due to Chlorofluorocarbons: Climatic Implications". Science, New Series 19: 50–52. JSTOR 1740877. 
  20. ^ a b Ramanathan, V; Y. Feng (2009). "Air pollution, greenhouse gases and climate change: Global and regional perspectives". Atmospheric Environment 43: 37–50. doi:10.1016/j.atmosenv.2008.09.063. 
  21. ^ Plummer LN and Busenberg E. 2006. "Chlorofluorocarbons in aquatic environments" (chapter 1), p. 1-8. In IAEA (ed.), Use of chlorofluorocarbons in hydrology – A guidebook: Vienna, International Atomic Energy Agency.
  22. ^ a b c Bulister JL and Wisegarver DP. 2008. "The shipboard analysis of trace levels of sulfur hexafluoride, chlorofluorocarbon-11 and chlorofluorocarbon-12 in seawater". Deep-Sea Res I; 55:1063-74.
  23. ^ Watanabe YW, Shimamoto A, and Ono T. 2003. "Comparison of time-dependent tracer ages in the Western North Pacific: oceanic background levels of SF6, CFC-11, CFC-12, and CFC-113". J Oceanogr.; 59:719-29.
  24. ^ a b c d e Fine RA. 2011. "Observations of CFCs and SF6 as ocean tracers". Ann Rev Mar Sci.; 3:173-95.
  25. ^ Warner MJ and Weiss RF. 1985. "Solubility of chlorofluorocarbons 11 and 12 in water and seawater". Deep-Sea Res.; 32:1485-97.
  26. ^ a b Min D, Warner MJ, and Bullister JL. 2010. "Estimated rates of carbon tetrachloride removal in the thermocline and deep waters of the East Sea (Sea of Japan)". Mar Chem.; 121:100-11.
  27. ^ a b c Bu X and Warner MJ. 1995. "Solubility of chlorofluorocarbon 113 in water and seawater". Deep-Sea Res I.; 42:1151–61
  28. ^ Wanninkhof R, Ledwell JR, and Watson AJ. 1991. "Analysis of sulfur hexafluoride in seawater". J Geophys Res.; 96:8733–40
  29. ^ Bullister JL, Wisegarver DP, and Menzia FA. 2002. "The solubility of sulfur hexafluoride in water and seawater". Deep-Sea Res I.; 49:175–87
  30. ^ Material Safety Data Sheet. National Refrigerants
  31. ^ WHO. "Fully Halogenated Chlorofluorocarbons". International Programme on Chemical Safety. Retrieved 04/12/2012. 

External links[edit]