Chemistry:1,1-Difluoroethane

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1,1-Difluoroethane[1]
Difluoroethane
Difluoroethane
Difluoroethane
Names
Preferred IUPAC name
1,1-Difluoroethane
Other names
  • Difluoroethane
  • Freon 152a
  • Ethylidene difluoride
  • Ethylidene fluoride
  • HFC-152a
  • R-152a
  • DFE
  • Tinned Wind
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
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 −24.7 °C (−12.5 °F; 248.5 K)
Critical point (T, P) 113.45 °C
0.54% @ 0 °C
Vapor pressure
  • 536 kPa (4020 mmHg) @ 21.1 °C
  • 510 kPa (5.1 bar) @ 20 °C
Viscosity 8.87 μPa·s (0.00887 cP) @ 25 °C
Hazards
Main hazards Extremely flammable
Safety data sheet SDS for 1,1-difluoroethane
GHS pictograms GHS02: Flammable GHS04: Compressed Gas
GHS Signal word DANGER
NFPA 704 (fire diamond)
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity 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
4
1
0
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
Tracking categories (test):

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]

Production

1,1-Difluoroethane is a synthetic substance that 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 (C2H3F), the monomeric precursor to polyvinyl fluoride.

Uses

With a relatively low global warming potential (GWP) index of 124 and favorable thermophysical properties, 1,1-difluoroethane has been proposed as an environmentally friendly alternative to R134a. Despite its flammability, R152a also presents operating pressures and volumetric cooling capacity (VCC) similar to R134a so it can be used in large chillers[5] or in more particular applications like heat pipe finned heat exchangers.[6]

Furthermore, 1,1-difluoroethane is also commonly used in gas dusters and numerous other retail aerosol products, particularly those subject to stringent volatile organic compound (VOC) requirements.

The molecular weight of difluoroethane is 66, making it a useful and convenient tool for detecting vacuum leaks in Gas chromatography–mass spectrometry (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,[7] 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

Difluoroethane is an extremely flammable gas, which decomposes rapidly on heating or burning, producing toxic and irritating fumes, including hydrogen fluoride and carbon monoxide.[8]

In a DuPont study, rats were exposed to up to 25,000 ppm (67,485 mg/m3) 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] Repeated or sufficiently high levels of exposure, particularly purposeful inhalation, can precipitate fatal cardiac arrhythmia.[10]

Abuse

Difluoroethane is an intoxicant with abuse potential.[10][11][12][13] Fatalities linked to difluoroethane abuse include actress Skye McCole Bartusiak, singer Aaron Carter and wrestler Mike Bell.[14] Bitterants, added voluntarily to some brands to deter purposeful inhalation, are often not legally required; they do not negate or counteract difluoroethane's intoxicating effects.

Environmental abundance

Growth of HFC-152a in Earth's atmosphere since year 2000.[15]
HFC-152a 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.


Most production, use, and emissions of HFC-152a have occurred within Earth's more industrialized and populated northern hemisphere following the substance's introduction in the 1990s. Its concentration in the northern troposphere reached an annual average of about 10 parts per trillion by year 2011.[15] The concentration of HFC-152a in the southern troposphere is about 50% lower due to its removal rate (i.e. lifetime) of about 1.5 years being similar in magnitude to the global atmospheric mixing time of one to two years.[16]

See also

References

  1. ↑ 1,1-Difluoroethane at Sigma-Aldrich
  2. ↑ "Changes in Atmospheric Constituents and in Radiative Forcing". Cambridge University Press. 2007. p. 212. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf.  18 February 2019
  3. ↑ "Global Warming Potentials of ODS Substitutes". U.S. Environmental Protection Agency. 2010. http://www.epa.gov/ozone/geninfo/gwps.html. 
  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. ISBN 978-3527306732. 
  5. ↑ Longo, Giovanni A.; Zilio, Claudio; Righetti, Giulia (2015). "Condensation of the low GWP refrigerant HFC152a inside a Brazed Plate Heat Exchanger". Experimental Thermal and Fluid Science 68: 509–515. doi:10.1016/j.expthermflusci.2015.06.010. 
  6. ↑ Righetti, Giulia; Zilio, Claudio; Mancin, Simone; Longo, Giovanni A. (2018). "Heat Pipe Finned Heat Exchanger for Heat Recovery: Experimental Results and Modeling". Heat Transfer Engineering 39 (12): 1011–1023. doi:10.1080/01457632.2017.1358483. Bibcode: 2018HTrEn..39.1011R. 
  7. ↑ Ethane, 1,1-difluoro- in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2023)
  8. ↑ "1,1-Difluoroethane". U.S. National Library of Medicine. https://webwiser.nlm.nih.gov/substance?substanceId=429&catId=61. 
  9. ↑ "1,1-Difluoroethane". National Library of Medicine HSDB Database. 1994. http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+75-37-6. 
  10. ↑ 10.0 10.1 "Fatal cardiac arrhythmia after repeated exposure to 1,1-difluoroethane (DFE)". The American Journal of Forensic Medicine and Pathology 27 (1): 58–60. March 2006. doi:10.1097/01.paf.0000202715.71009.0e. PMID 16501351. 
  11. ↑ "Two traffic fatalities related to the use of difluoroethane". Journal of Forensic Sciences 42 (6): 1186–7. November 1997. doi:10.1520/JFS14284J. PMID 9397568. 
  12. ↑ 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. 
  13. ↑ "Autopsy: man in crash died from inhaling computer cleaner". The Times News. 10 March 2012. http://www.thetimesnews.com/news/died-53343-cleaner-computer.html. 
  14. ↑ Duke, Alan (22 July 2014). "'Patriot' actress Skye McCole Bartusiak dead at 21". CNN. https://www.cnn.com/2014/07/20/showbiz/obit-skyemccolebartusiak/index.html. 
  15. ↑ 15.0 15.1 "HFC-152a". NOAA Earth System Research Laboratories/Global Monitoring Division. https://www.esrl.noaa.gov/gmd/hats/gases/HFC152a.html. Retrieved 2021-02-12. 
  16. ↑ Greally, B.R. (2007). "Observations of 1,1-difluoroethane (HFC-152a) at AGAGE and SOGE monitoring stations in 1994–2004 and derived global and regional emission estimates". Journal of Geophysical Research 112 (D06308). doi:10.1029/2006JD007527. Bibcode: 2007JGRD..112.6308G. 



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