Dichlorodifluoromethane

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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 YesY
PubChem 6391
ChemSpider 6151 YesY
UNII OFM06SG1KO YesY
EC number 200-893-9
UN number 1028
KEGG D03789 YesY
RTECS number PA8200000
Jmol-3D images Image 1
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; −251.9 °F; 115.5 K
Boiling point −29.8 °C; −21.6 °F; 243.3 K
Solubility in water 0.286 g/l at 20 °C
Solubility in alcohol, ether, benzene, acetic acid Soluble
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
R-phrases R44 R59[1]
S-phrases S9 S38[1]
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
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 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 1996 due to concerns about damage to the ozone layer.[2] It is soluble in many organic solvents. Dichlorodifluoromethane was also the main component of Silly String. R-12 cylinders are colored white.

Preparation

It can be prepared by reacting carbon tetrachloride with hydrogen fluoride in the presence of a catalytic amount of antimony pentachloride:

CCl4 + 2HF → CCl2F2 + 2HCl

This reaction can also produce trichlorofluoromethane (CCl3F), chlorotrifluoromethane (CClF3) and tetrafluoromethane (CF4).[3]

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 is not known to harm the environment has been chosen as the replacement.[4]

Retrofitting

R-12 was used in most refrigeration and vehicle air conditioning applications prior to 1994 before being replaced by 1,1,1,2-tetrafluoroethane (R-134a), which has an insignificant ozone depletion potential. 1992–1994 was the time period in which automobile manufacturers started using R-134a instead of R-12. When older units leak, retrofits to R-134a are recommended. Retrofit to R-134a requires 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, an 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. Note that the instructions for R-409A recommend charging a system with liquid to keep the mixture ratios constant. The constituents have varying vapor pressures.

R-414A is designed as a drop-in replacement (substitute) for R-12.

Gallery

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

  • 1990s sea surface CFC-12 concentration

  • 1990s CFC-12 oceanic vertical inventory

  • CFC-12, CFC-11, H-1211 and SF6 vertical profiles

References

  1. ↑ 1.0 1.1 "Dichlorodifluoromethane MSDS". Synquest Labs. 
  2. ↑ The Ozone Hole-The Montreal Protocol on Substances that Deplete the Ozone Layer
  3. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 304. ISBN 0080379419. 
  4. ↑ 'Rescue' asthma inhaler replacements coming to Pa.

External links

Monosubstituted
Disubstituted
Trisubstituted
Tetrasubstituted
* Chiral compound.
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