Dichlorodifluoromethane

Dichlorodifluoromethane
Names
Preferred IUPAC name
Dichloro(difluoro)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
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.000.813
EC Number 200-893-9
E number E940 (glazing agents, ...)
KEGG
RTECS number PA8200000
UNII
UN number 1028
Properties
CCl2F2
Molar mass 120.91 g·mol−1
Appearance Colorless gas with ether-like odor
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)
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))
0.0025 mol kg−1 bar−1
-52.2·10−6 cm3/mol
Structure
Tetrahedral
0.51 D[1]
Hazards
Main hazards Damaging to Earth's protective ozone
Safety data sheet See: data page
R-phrases (outdated) R44 R59[2]
S-phrases (outdated) S9 S38[2]
NFPA 704
Flammability code 0: Will not burn. E.g., waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
0
0
Flash point Non-flammable [3]
Lethal dose or concentration (LD, LC):
760,000 ppm (mouse, 30 min)
800,000 ppm (rabbit, 30 min)
800,000 ppm (guinea pig, 30 min)
600,000 ppm (rat, 2 hr)[4]
US health exposure limits (NIOSH):
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
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
 Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is ☑Y☒N ?)
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. Complying with the Montreal Protocol, its manufacture was banned in developed countries (non-article 5 countries) in 1996, and developing countries (article 5 countries) in 2010 due to concerns about its damaging impact to the ozone layer.[5] Its only allowed usage is as fire retardant in submarines and aircraft. It is soluble in many organic solvents. Dichlorodifluoromethane was one of the original propellants for 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).[6]

History

Charles (Boss) 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 is 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) 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 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.

References

  1. ↑ Khristenko, Sergei V.; Maslov, Alexander I. and Viatcheslav P. Shevelko; Molecules and Their Spectroscopic Properties, p. 74 ISBN 3642719481
  2. 1 2 "Dichlorodifluoromethane MSDS" (PDF). Synquest Labs.
  3. 1 2 3 4 "NIOSH Pocket Guide to Chemical Hazards #0192". National Institute for Occupational Safety and Health (NIOSH).
  4. ↑ "Dichlorodifluoromethane". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. ↑ "Dichlorodifluoromethane at LearnChemistry (Royal Society of Chemistry)". rsc.org. Retrieved 2017-11-29.
  6. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 304. ISBN 0-08-037941-9.
  7. ↑ Plunkett, Roy J. (1986). High Performance Polymers: Their Origin and Development. Elsevier Science Publishing Co. , Inc. pp. 261–262. ISBN 978-94-011-7073-4.
  8. ↑ 'Rescue' asthma inhaler replacements coming to Pa. Archived February 16, 2007, at the Wayback Machine.
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