1,1-Difluoroethane

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]

1,1-Difluoroethane^[1]

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
CAS Number	75-37-6 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL325493 Y
ChemSpider	6128 Y
ECHA InfoCard	100.000.788
PubChem CID	6368
RTECS number	KI1410000
UNII	0B1U8K2ME0 Y
CompTox Dashboard (EPA)	DTXSID0024050
InChI InChI=1S/C2H4F2/c1-2(3)4/h2H,1H3 Y Key: NPNPZTNLOVBDOC-UHFFFAOYSA-N Y InChI=1/C2H4F2/c1-2(3)4/h2H,1H3 Key: NPNPZTNLOVBDOC-UHFFFAOYAM
SMILES FC(F)C
Properties
Chemical formula	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
Solubility in water	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
Occupational safety and health (OHS/OSH):
Main hazards	Extremely flammable
GHS labelling:
Pictograms
Signal word	Danger
NFPA 704 (fire diamond)	1 4 0
Safety data sheet (SDS)	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). Y verify (what is YN ?) Infobox references

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]

In addition, 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]} It appears to act primarily through GABA_A and glutamate receptors.^[14][15] Fatalities linked to difluoroethane abuse include actress Skye McCole Bartusiak, singer Aaron Carter and wrestler Mike Bell.^[16] 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.^[17]

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.^[17] 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.^[18]

See also

• List of refrigerants
• IPCC list of greenhouse gases
• Canned air

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. 18 February 2019
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. (eds.). 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. Bibcode:2018HTrEn..39.1011R. doi:10.1080/01457632.2017.1358483. S2CID 126263840.
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) (retrieved 2023)
8. "1,1-Difluoroethane". WebWISER. U.S. National Library of Medicine. Retrieved 2 April 2022.
9. "1,1-Difluoroethane". National Library of Medicine HSDB Database. 1994. Retrieved 8 June 2010.
10. 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. S2CID 22312214.
11. 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. 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. Archived from the original on 12 March 2012.
14. Novotny, Clara B; Irvin, Sarah; Espiridion, Eduardo D (2019). "Acute Psychosis Following 1,1-Difluoroethane Inhalation". Cureus. 11 (9): e5565. doi:10.7759/cureus.5565. ISSN 2168-8184. PMC 6820689. PMID 31695984.
15. Custer, Adam; Corse, Andrew; Vazirani, Sondra (June 2020). "Difluoroethane Inhalant Abuse, Skeletal Fluorosis, and Withdrawal". Federal Practitioner. 37 (6): 288–289. ISSN 1078-4497. PMC 7357883. PMID 32669782.
16. Duke, Alan (22 July 2014). "'Patriot' actress Skye McCole Bartusiak dead at 21". CNN. Retrieved 24 February 2019.
17. "HFC-152a". NOAA Earth System Research Laboratories/Global Monitoring Division. Retrieved 12 February 2021.
18. Greally, B.R.; et al. (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). Bibcode:2007JGRD..112.6308G. doi:10.1029/2006JD007527.