Dichlorodifluoromethane

Dichlorodifluoromethane
IUPAC name Dichlorodifluoromethane
Other names Carbon dichloride difluoride, Dichloro-difluoro-methane, Difluorodichloromethane, Freon 12, R-12, CFC-12, P-12, Propellant 12, Halon 122, Arcton 6, Arcton 12, E940
Identifiers
CAS number	75-71-8 Y
PubChem	6391
ChemSpider	6151 Y
UNII	OFM06SG1KO Y
EC number	200-893-9
UN number	1028
KEGG	D03789 Y
RTECS number	PA8200000
Jmol-3D images	Image 1
SMILES ClC(Cl)(F)F
InChI InChI=1S/CCl2F2/c2-1(3,4)5 Y Key: PXBRQCKWGAHEHS-UHFFFAOYSA-N Y InChI=1/CCl2F2/c2-1(3,4)5 Key: PXBRQCKWGAHEHS-UHFFFAOYAX
Properties
Molecular formula	CCl2F2
Molar mass	120.91 g mol−1
Appearance	Colorless gas with ether-like odor
Density	1.486 g/cm³ (−29.8 °C)
Melting point	-157.7 °C, 115 K, -252 °F
Boiling point	-29.8 °C, 243 K, -22 °F
Solubility in water	0.286 g/l at 20 °C
log P	2.16
Vapor pressure	568 kPa (20 °C)
kH	0.0025 mol kg-1 bar-1
Hazards
MSDS	External MSDS
EU Index	Not listed
Main hazards	Damaging to Earth's protective ozone
Flash point	Non-flammable
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Dichlorodifluoromethane (R-12), is a colorless gas, and usually sold under the brand name Freon-12, is a chlorofluorocarbon halomethane (CFC), used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in the United States along with many other countries in 1994 due to concerns about damage to the ozone layer.^[1] It is soluble in many organic solvents.

Use as an aerosol

The use of chlorofluorocarbons as an aerosol in medicine, for example: USP-approved salbutamol, has been phased out by the U.S. Food and Drug Administration. The use of a different propellant known as hydrofluoroalkane, or HFA, which does not harm the environment has been chosen as the replacement.^[2]

Retrofitting

R-12 was used in most refrigeration and vehicle air conditioning applications prior to 1994 before being replaced by R-134a, which has a lower ozone depletion potential. When older units leak, retrofits to (1,1,1,2-tetrafluoroethane) are recommended. Retrofits to R-134a require complete flushing and filter/dryer replacement to remove the mineral oil. Mineral oil used for R12 is not compatible with R-134a. Some oils designed for conversion to R-134a are advertised as compatible with residual R-12. New rubber hoses which are R-134a compatible may be needed for the same reason.

In systems where R-134a is not practical, a R-409A blend (60% R-22; 25% R-124; 15% R-142b) may be directly added to an R-12 system without oil change although a filter change is always recommended. R-409A usually runs on the low-pressure side of the system at 12 pounds per square inch (psi), while R-12 usually runs on the low side at 10 psi. R-409A runs at higher pressures and is less efficient but works quite well. Manufacturer recommends that existing R-12 charge should be recovered. However, as the two refrigerants are soluble in the same mineral oil there are no complications associated with mixing them.

Gallery

• 

  Time-series of atmospheric concentrations of CFC-12 (Walker et al., 2000)

• 

  "Present day" (1990s) sea surface CFC-12 concentration

• 

  "Present day" (1990s) CFC-12 oceanic vertical inventory

References

1. ^ The Ozone Hole-The Montreal Protocol on Substances that Deplete the Ozone Layer
2. ^ 'Rescue' asthma inhaler replacements coming to Pa.

External links

• NOAA/ESRL CFC-12 global measurements
• International Chemical Safety Card 0048
• Overview of Freon-12 and some of its environmental problems
• MSDS at Oxford University
• Thermochemistry data at chemnet.ru
• IR absorption spectra