Chlorodifluoromethane Identifiers CAS number PubChem ChemSpider EC number KEGG ChEMBL RTECS number PA6390000 Jmol-3D images Image 1 Properties Molecular formula CHClF2 Molar mass 86.47 g/mol Appearance Colorless gas Density 3.66 kg/m3 at 15°C, gas Melting point
-175.42 °C, 98 K, -284 °F
-40.7 °C, 232 K, -41 °F
Solubility in water 0.7799 vol/vol at 25 °C; 3.628 g/L log P 1.08 Vapor pressure 908 kPa at 20 °C kH 0.033 mol.kg-1.bar-1 Structure Molecular shape Tetrahedral Hazards R-phrases S-phrases Main hazards Dangerous for the environment (N), Central nervous system depressant, Carc. Cat. 3 NFPA 704 Autoignition
632 °C (what is: /?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22. It was once commonly used as a propellant and in air conditioning applications. These applications are being phased out due to ozone depletion potential and status as a potent greenhouse gas, with a high global warming potential. R22 is a versatile intermediate in industrial organofluorine chemistry, e.g. as a precursor to tetrafluoroethylene.
Production and current applications
Chlorodifluoromethane is prepared from chloroform:
- HCCl3 + 2 HF → HCF2Cl + 2 HCl
- 2 CHClF2 → C2F4 + 2 HCl
The compound also yields difluorocarbene upon treatment with strong base and is used in the laboratory as a source of this reactive intermediate.
The pyrolysis of R22 in the presence of chlorofluoromethane gives hexafluorobenzene.
Chlorodifluoromethane was used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential of 0.055, among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable.
As an additional environmental concern, chlorodifluoromethane has a global warming potential that is 1810 (1810 times that of carbon dioxide). HFCs such as R-410A have high global warming potential, but has an ODP (or ozone depletion potential) of 0. The GWP of propane (R-290), for example, is only 3.
It will be phased out soon under the Montreal Protocol, to be replaced by other refrigerants with lower ozone depletion potential such as propane (R-290), R-410A (an azeotropic mixture of difluoromethane and pentafluoroethane), R-507A, R-134a (1,1,1,2-tetrafluoroethane) and R-409A. 
- Beginning January 1, 2004: The Montreal Protocol required the U.S. to reduce its consumption of HCFCs by 35% below the U.S. baseline cap. As of January 1, 2003, EPA banned production and import of HCFC-141b, the most ozone-destructive HCFC. This action allowed the United States to meet its obligations under the Montreal Protocol. EPA was able to issue 100% of company baseline allowances for production and import of HCFC-22 and HCFC-142b.
- Beginning January 1, 2010: The Montreal Protocol requires the U.S. to reduce its consumption of HCFCs by 75% below the U.S. baseline. Allowance holders may only produce or import HCFC-22 to service existing equipment. Virgin R-22 may not be used in new equipment. As a result, heating, ventilation and air-conditioning (HVAC) system manufacturers may not produce new air conditioners and heat pumps containing R-22.
- Beginning January 1, 2015: The Montreal Protocol requires the U.S. to reduce its consumption of HCFCs by 90% below the U.S. baseline.
- Beginning January 1, 2020: The Montreal Protocol requires the U.S. to reduce its consumption of HCFCs by 99.5% below the U.S. baseline. Refrigerant that has been recovered and recycled/reclaimed will be allowed beyond 2020 to service existing systems, but chemical manufacturers will no longer be able to produce R-22 to service existing air conditioners and heat pumps.
Beginning in 2010 in the U.S., the production and importing of HCFC-22 will be limited to 25% of each country's 1989 consumption level. New and imported HCFC-22 will be available only for use in equipment manufactured before 1/1/2010.
On January 1, 2010, it became illegal to import, produce, or sell R-22 for use in new equipment or pre-charged in new equipment. In 2015, the production and importing of HCFC-22 will be limited to 10% of each country's 1989 consumption level and in 2020, production and importing of HCFC-22 will be illegal. Re-use of recovered HCFC-22 to service existing equipment will be allowed indefinitely.
Property Value Density (ρ) at -69 °C (liquid) 1.49 g.cm−3 Density (ρ) at -41 °C (liquid) 1.413 g.cm−3 Density (ρ) at -41 °C (gas) 4.706 kg.m−3 Density (ρ) at 15 °C (gas) 3.66 kg.m−3 Specific gravity at 21 °C (gas) 3.08 (air = 1) Specific volume (ν) at 21 °C (gas) 0.275 m³.kg−1 Density (ρ) at 15 °C (gas) 3.66 kg.m−3 Triple point temperature (Tt) -157.39 °C (115.76 K) Critical temperature (Tc) 96.2 °C (369.3 K) Critical pressure (pc) 4.936 MPa (49.36 bar) Critical density (ρc) 6.1 mol.l−1 Latent heat of vaporization (lv) at boiling point (-40.7 °C) 233.95 kJ.kg−1 Heat capacity at constant pressure (Cp) at 30 °C (86 °F) 0.057 kJ.mol−1.K−1 Heat capacity at constant volume (Cv) at 30 °C (86 °F) 0.048 kJ.mol−1.K−1 Heat capacity ratio (γ) at 30 °C (86 °F) 1.178253 Compressibility factor (Z) at 15 °C 0.9831 Acentric factor (ω) 0.22082 Molecular dipole moment 1.458 D Viscosity (η) at 0 °C 12.56 µPa.s (0.1256 cP) Ozone depletion potential (ODP) 0.055 (CCl3F = 1) Global warming potential (GWP) 1810 (CO2 = 1)
It has two allotropes: crystalline II below 59 K and crystalline I above 59 K to 115.73 K.
- MSDS at Oxford University
- International Chemical Safety Card 0049
- Data at Integrated Risk Information System: IRIS 0657
- Phase change data at webbook.nist.gov
- IR absorption spectra
- IARC Summaries & Evaluations: Vol. 41 (1986), Suppl. 7 (1987), Vol. 71 (1999)
- ^ 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
- ^ The Montreal Protocol on Substances that Deplete the Ozone Layer. UNEP, 2000. ISBN 92-807-1888-6
- ^ IPCC (2007), Changes in Atmospheric Constituentsand in Radiative Forcing, http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf
- ^ http://www.epa.gov/ozone/title6/phaseout/22phaseout.html EPA Phase-out
Halomethanes Monosubstituted Disubstituted Trisubstituted
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