Chlorodifluoromethane
From Wikipedia, the free encyclopedia
| Chlorodifluoromethane | |
|---|---|
 |
 |
| IUPAC name | Chlorodifluoromethane |
| Other names | Difluoromonochloromethane, Monochlorodifluoromethane, HCFC-22, R-22, Genetron 22, Freon 22, Arcton 4, Arcton 22, UN 1018 |
| Identifiers | |
| CAS number | [75-45-6] |
| PubChem | |
| EINECS number | |
| KEGG | |
| RTECS number | PA6390000 |
| SMILES | C(F)(F)Cl |
| InChI | 1/CHClF2/c2-1(3)4/h1H |
| 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 (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 mol.kg-1.bar-1 |
| Structure | |
| Molecular shape | Tetrahedral |
| Hazards | |
| Main hazards | Dangerous for the environment (N), Central nervous system depressant, Carc. Cat. 3 |
| NFPA 704 |
 0
1
1
|
| R-phrases | R59 |
| S-phrases | S23, S24, S25, S59 |
| Autoignition temperature |
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. It will soon be phased out due to ozone depletion potential and status as a potent greenhouse gas.
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.
Contents |
[edit] Environmental effects and phase-out
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,[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.
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.[citations needed]
[edit] Physical Properties
| 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 |
| 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) | 1700 (CO2 = 1) |
It has two allotropes: crystaline II below 59 K and crystaline I above 59 K to 115.73 K.
[edit] See also
- Haloalkane
- Halomethane
- Trihalomethane
- Hydrochlorofluorocarbon
- Chlorofluoromethane
- Difluoromethane
- Dichlorodifluoromethane
- Chlorotrifluoromethane
[edit] External links
- 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)
[edit] References
- ^ The Montreal Protocol on Substances that Deplete the Ozone Layer. UNEP, 2000. ISBN 92-807-1888-6
- ^ Comfort Air Conditioning list of Refrigerants, http://www.comfort.uk.com/refrigerants.htm
