Dichlorodifluoromethane

Dichlorodifluoromethane

Names
Preferred IUPAC name Dichlorodi(fluoro)methane
Other names Dichlorodifluoromethane Carbon dichloride difluoride Dichloro-difluoro-methane Difluorodichloromethane Freon 12 R-12 CFC-12 P-12 Propellant 12 Halon 122 Arcton 6 Arcton 12 E940 Fluorocarbon 12 Genetron 12 Refrigerant 12
Identifiers
CAS Number	75-71-8 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL2106634 N
ChemSpider	6151 Y
ECHA InfoCard	100.000.813
EC Number	200-893-9
E number	E940 (glazing agents, ...)
KEGG	D03789 Y
PubChem CID	6391
RTECS number	PA8200000
UNII	OFM06SG1KO Y
UN number	1028
CompTox Dashboard (EPA)	DTXSID6020436
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
SMILES ClC(Cl)(F)F
Properties
Chemical formula	CCl2F2
Molar mass	120.91 g·mol−1
Appearance	Colorless gas
Odor	ether-like at very high concentrations
Density	1.486 g/cm3 (−29.8 °C (−21.6 °F))
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 (68 °F)
Solubility in alcohol, ether, benzene, acetic acid	Soluble
log P	2.16
Vapor pressure	568 kPa (20 °C (68 °F))
Henry's law constant (kH)	0.0025 mol kg−1 bar−1
Magnetic susceptibility (χ)	−52.2·10−6 cm3/mol
Thermal conductivity	0.0097 W/(m·K) (300 K)[1]
Structure
Molecular shape	Tetrahedral
Dipole moment	0.51 D[2]
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H280, H336, H420
Precautionary statements	P261, P271, P304+P340, P319, P403+P233, P405, P410+P403, P501, P502
NFPA 704 (fire diamond)	0 0 0
Flash point	Non-flammable[3]
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	760,000 ppm (mouse, 30 min) 800,000 ppm (rabbit, 30 min) 800,000 ppm (guinea pig, 30 min) 600,000 ppm (rat, 2 h)[4]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1000 ppm (4950 mg/m3)[3]
REL (Recommended)	TWA 1000 ppm (4950 mg/m3)[3]
IDLH (Immediate danger)	15000 ppm[3]
Supplementary data page
Dichlorodifluoromethane (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Dichlorodifluoromethane (R-12) is a colorless gas usually sold under the brand name Freon-12, and a chlorofluorocarbon halomethane (CFC) used as a refrigerant and aerosol spray propellant. In compliance with the Montreal Protocol, its manufacture was banned in developed countries (non-article 5 countries) in 1996, and in developing countries (Article 5 countries) in 2010 out of concerns about its damaging effect on the ozone layer.^[5] Its only allowed usage is as a fire retardant in submarines and aircraft. It is soluble in many organic solvents. 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).^[6]

History

Charles Kettering, vice president of General Motors Research Corporation, was seeking a refrigerant replacement that would be colorless, odorless, tasteless, nontoxic, and nonflammable. He assembled a team that included Thomas Midgley, Jr., Albert Leon Henne, and Robert McNary. From 1930 to 1935, they developed dichlorodifluoromethane (CCl₂F₂ or R12), trichlorofluoromethane (CCl₃F or R11), chlorodifluoromethane (CHClF₂ or R22), trichlorotrifluoroethane (CCl₂FCClF₂ or R113), and dichlorotetrafluoroethane (CClF₂CClF₂ or R114), through Kinetic Chemicals which was a joint venture between DuPont and General Motors.^[7]

Use as an aerosol

The use of chlorofluorocarbons as aerosols in medicine, such as USP-approved salbutamol, has been phased out by the U.S. Food and Drug Administration. A different propellant known as hydrofluoroalkane, or HFA, which was not known to harm the environment, was chosen to replace it.^[8]

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. Automobile manufacturers started using R-134a instead of R-12 in 1992–1994. When older units leak or require repair involving removal of the refrigerant, retrofitment to a refrigerant other than R-12 (most commonly R-134a which has a global warming potential 3,400 times that of carbon dioxide) is required in some jurisdictions. The United States does not require automobile owners to retrofit their systems; however, taxes on ozone-depleting chemicals coupled with the relative scarcity of the original refrigerants on the open market make retrofitting the only economical option. Retrofitment requires a system flush and a new filter/dryer or accumulator, and may also involve the installation of new seals and/or hoses made of materials compatible with the refrigerant being installed. Mineral oil used with R-12 is not compatible with R-134a. Some oils designed for conversion to R-134a are advertised as compatible with residual R-12 mineral oil. Another replacement for R-12 is the highly flammable, but truly drop-in HC-12a, whose flammability has led to injuries and deaths in a bus fire in 2006.^[9][10]

Dangers

Aside from its environmental impacts, R12, like most chlorofluoroalkanes, forms phosgene gas when exposed to a naked flame.^[11]

Properties

Table of thermal and physical properties of saturated liquid refrigerant 12:^[12][13]

Gallery

• 
  CFC-12 measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.
• 
  Hemispheric and global mean CFC-12 concentrations (NOAA/ESRL)
• 
  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

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
• CDC - NIOSH Pocket Guide to Chemical Hazards