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For the Robinson R22 helicopter, see Robinson R22.
IUPAC name Chlorodifluoromethane
Other names Difluoromonochloromethane, Monochlorodifluoromethane, HCFC-22, R-22, Genetron 22, Freon 22, Arcton 4, Arcton 22, UN 1018
CAS number 75-45-6
PubChem 6372
EINECS number 200-871-9
KEGG D03789
RTECS number PA6390000
InChI InChI=1/CHClF2/c2-1(3)4/h1H
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 (97.73 K)

Boiling point

-40.7 C (232.45 K)

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
Molecular shape Tetrahedral
Main hazards Dangerous for the environment (N), Central nervous system depressant, Carc. Cat. 3
NFPA 704
R-phrases R59
S-phrases S23, S24, S25, S59
632 °C
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). It is better known under its code names of HCFC-22, R-22, Genetron 22 or Freon 22, and is commonly used in air conditioning applications, such as residential split systems in the US, rooftop units and window air conditioners.

Additional recommended knowledge

Chlorodifluoromethane was first 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,[1] among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable it will be phased out soon under the Montreal Protocol, to be replaced by refrigerants with zero ozone depletion potential such as Propane (R-290), and other refrigerants (even though they don't have very similar properties): R-410A (an azeotropic mixture of difluoromethane and pentafluoroethane), R-502, R-134a (1,1,1,2-tetrafluroethane) and R-409A.

An additional environmental concern regarding Chlorodifluoromethane, as well as some of the proposed replacements, is their global warming potential. The global warming potential of Chlorodifluoromethane is 1700 (1700 times that of carbon dioxide)[2]. HFCs such as R-410A have high global warming potential, whereas that of propane (R-290) is only 3.

It is an intermediate in the synthesis of tetrafluoroethylene, into which it is converted by pyrolysis. Difluorocarbene is an intermediate in this reaction. The compound also yields difluorocarbene upon treatment with strong base and is used in the laboratory as a source of this reactive intermediate.

The US EPA has enacted regulation which will phase out the use of HCFC-22 in the near future. Air conditioning manufacturers will no longer be allowed to sell R22 equipment as of January 1, 2010. In the aftermarket service business, the allocation rights for producers who manufacture R22 will be cut each year making the remaining R22 supply potentially smaller than the service demand for the product. This could make R22 scarce in the future, and drive prices to consumers higher.

Physical Properties

Property Value
Density (ρ) at -69 °C (liquid) 1.49
Density (ρ) at -41 °C (liquid) 1.413
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
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
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) 1900 (CO2 = 1)

It has two allotropes: crystaline II below 59 K and crystaline I above 59 K to 115.73 K.

See also


  1. ^ The Montreal Protocol on Substances that Deplete the Ozone Layer. UNEP, 2000. ISBN 92-807-1888-6
  2. ^ Comfort Air Conditioning list of Refrigerants,
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chlorodifluoromethane". A list of authors is available in Wikipedia.
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