1,1-Difluoroethane

1,1-Difluoroethane[1]
Names
Preferred IUPAC name
1,1-Difluoroethane
Other names
Difluoroethane
Freon 152a
Ethylidene difluoride
Ethylidene fluoride
HFC-152a
R-152a
DFE
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.000.788
RTECS number KI1410000
UNII
Properties
C2H4F2
Molar mass 66.05 g/mol
Density 900 g/L @ 25 °C
Melting point −117 °C (−179 °F; 156 K)
Boiling point −25 °C (−13 °F; 248 K)
0.54% @ 0 °C
Vapor pressure 4020 mmHg/536 kPa @ 21.1 °C

5.1 bar/510 kPa @ 20 °C

Viscosity 0.00887 cP (8.87 µPa·s) @ 25 °C
Hazards
Safety data sheet SDS for 1,1-difluoroethane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula C2H4F2. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-152a). It is also used as a propellant for aerosol sprays and in gas duster products. As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years).[2][3] It has recently been approved for use in automobile applications as an alternative to R-134a.

Production

1,1-Difluoroethane is produced by the mercury-catalyzed addition of hydrogen fluoride to acetylene:[4]

HCCH + 2 HF → CH3CHF2

The intermediate in this process is vinyl fluoride, the monomeric precursor to polyvinyl fluoride.

Uses

In addition to serving as a refrigerant, 1,1-difluoroethane is also commonly used in gas duster (commonly thought of as "canned air") and many consumer aerosol products, especially those subject to stringent VOC requirements.

The molecular weight of difluoroethane is 66, making it a useful and convenient tool for detecting vacuum leaks in GC-MS systems. The cheap and freely available gas has a molecular weight and fragmentation pattern (base peak 51 m/z in typical EI-MS, major peak at 65 m/z) distinct from anything in air. If mass peaks corresponding to 1,1-difluoroethane are observed immediately after spraying a suspect leak point, leaks may be identified.

Safety

The practice of deliberately inhaling or “huffing” canned air can be fatal. Though often overlooked due to lack of identification via common drug screens, it has caused the instantaneous deaths of numerous individuals by precipitating fatal cardiac arrhythmia.[5] Several reports of fatal car crashes have been linked to drivers huffing 1,1-difluoroethane.[6][7][8] Because of inhalant abuse, a bitterant is often added to consumer canned air products.

In a DuPont study, rats were exposed to up to 25,000 ppm (67,485 mg m−3) for six hours daily, five days a week for two years. This has become the no-observed-adverse-effect level for this substance. Prolonged exposure to 1,1-difluoroethane has been linked in humans to the development of coronary disease and angina.[9]

Though not extremely flammable in gaseous form, 1,1-difluoroethane can burn under some conditions. As such, there is also a warning label present on some gas dusters. When inverted to spray liquid, the boiling fluorocarbon aerosol is easily ignitable, producing a very large blast of flame and extremely toxic gases such as hydrogen fluoride and carbonyl fluoride as combustion products.

See also

References

  1. ↑ 1,1-Difluoroethane at Sigma-Aldrich
  2. ↑ "Changes in Atmospheric Constituents and in Radiative Forcing" (PDF). Cambridge University Press. 2007. p. 212. Retrieved 11 May 2017.
  3. ↑ "Global Warming Potentials of ODS Substitutes". U.S. Environmental Protection Agency. 2010. Archived from the original on 16 October 2010. Retrieved 20 September 2010.
  4. ↑ Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2010). "Fluorine Compounds, Organic". In Bohnet, Matthias; Bellussi, Giuseppe; Bus, James; et al. Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons. doi:10.1002/14356007.a11_349.
  5. ↑ Avella J, Wilson JC, Lehrer M (March 2006). "Fatal cardiac arrhythmia after repeated exposure to 1,1-difluoroethane (DFE)". The American Journal of Forensic Medicine and Pathology. 27 (1): 58–60. doi:10.1097/01.paf.0000202715.71009.0e. PMID 16501351.
  6. ↑ Broussard LA, Brustowicz T, Pittman T, Atkins KD, Presley L (November 1997). "Two traffic fatalities related to the use of difluoroethane". Journal of Forensic Sciences. 42 (6): 1186–7. PMID 9397568.
  7. ↑ Hahn, T; Avella, J; Lehrer, M (2006). "A motor vehicle accident fatality involving the inhalation of 1,1-difluoroethane". Journal of analytical toxicology. 30 (8): 638–42. doi:10.1093/jat/30.8.638. PMID 17132266.
  8. ↑ "Autopsy: man in crash died from inhaling computer cleaner". The Times News. 10 March 2012. Archived from the original on 12 March 2012.
  9. ↑ "1,1-Difluoroethane". National Library of Medicine HSDB Database. 1994. Retrieved 8 June 2010.
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