1,1,1,2-Tetrafluoroethane

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1,1,1,2-Tetrafluoroethane
IUPAC name 1,1,1,2-tetrafluoroethane
Other names Genetron 134a
HFC-134a
R-134a
Freon 134a
Norflurane
Identifiers
3D model (JSmol)
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RTECS number KI8842500
Properties
C2H2F4
Molar mass 102.03 g/mol
Appearance Colorless gas.
Density 0.00425 g/cm³, gas.
Melting point
Boiling point
Structure
Molecular shape Planar.
Hazards
Main hazards Asphyxiant.
S-phrases (S2), S23, S24/25, S51.
Flash point {{{value}}}
Related compounds
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Freon 134a or HFC-134a, is a haloalkane refrigerant without an ozone depletion potential and thermodynamic properties similar to R-12 (dichlorodifluoromethane). It has the formula CH2FCF3, and a boiling point of −26.6 °C (−15.9 °F).

Uses

1,1,1,2-Tetrafluoroethane is an inert gas used primarily as a "high-temperature" refrigerant for domestic refrigeration and automobile air conditioners. Other uses include plastic foam blowing, as a cleaning solvent and as a propellant for the delivery of pharmaceuticals (e.g. bronchodilators), gas dusters, and in air driers, that is, for removing the moisture from compressed air. Moisture present in compressed air has a harmful effect on pneumatic systems. Tetrafluoroethane has also been used to cool computers in some overclocking attempts. It is also commonly used as a power source for airsoft airguns.

Tetrafluoroethane is a clear liquid which boils at room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use.

Recently, R-134a has been subject to use restrictions due to its theorized contribution to climate change. In the EU, it will be banned as from 2011 in all new cars[1], and California may prohibit the sale of canned HFC-134a to individuals to avoid non-professional recharge of the air conditioner.[2]

History

R-134a first appeared in the early 1990s as a replacement for Dichlorodifluoromethane (R-12), which has significant ozone depleting properties.[3] R-134a has been atmospherically modeled for its impact on depleting ozone and as a contributor to global warming. Research suggests that over the past 10 years the concentration of 1,1,1,2-tetrafluoroethane has increased significantly in the Earth atmosphere, with a recent study revealing a doubling in atmospheric concentration between 2001-2004.[4] It has insignificant ozone depletion potential (ozone layer), significant global warming potential (GWP100 = 1300) and negligible acidification potential (acid rain). 1,1,1,2-Tetrafluoroethane is slowly converted to trifluoroacetic acid through a radical reaction in the upper atmosphere and leads to a detectable amount of several ng/L in acid rain.[5]

Safety

Contact of tetrafluoroethane with flames or hot surfaces in excess of 250°C (482°F) may cause vapor decomposition and the emission of toxic gases including hydrogen fluoride and carbonyl halides.[6] Tetrafluoroethane itself has an LC50 (lethal concentration for 50% of subjects) in rats of 1,500 g/m³, making it relatively non-toxic. However, its gaseous form is denser than air, and will displace air in the lungs. This can result in asphyxiation if excessively inhaled.[7][8]

Aerosol cans containing tetrafluoroethane, when inverted, become effective freeze sprays. Under pressure, tetrafluoroethane is compressed into a liquid, which upon vaporization absorbs a significant amount of thermal energy. As a result, it will greatly lower the temperature of any object it contacts as it evaporates. This can result in frostbite when contacting skin.

References

  1. European Directive 2006/40/EC relating to emissions from air-conditioning systems in motor vehicles
  2. Early Action Measure California: Use ban of canned HFC-134a
  3. Franklin J (1993). "The Atmospheric Degradation and Impact of 1,1,1,2-Tetrafluorethane (Hydrofluorocarbon 134a)". Chemosphere. 27: 1565–1601. doi:10.1016/0045-6535(93)90251-Y.
  4. "Greenhouse gas monitoring at the Zeppelin station - Annual report 2004 (TA-2110/2005)" (PDF). Norwegian Institute for Air Research. Retrieved 2006-01019. Check date values in: |accessdate= (help)
  5. von Sydow L, Grimvall AB, Borén HB, Laniewski K, Nielsen AT (2000). "Natural Background Levels of Trifluoroacetate in Rain and Snow". Enviro Sci Technol. 34: 3115–3118. doi:10.1021/es9913683.
  6. Honeywell International (December 2005). "MSDS # GTRN-0047 For Genetron® 134aUV".
  7. Alexander D. J, Libretto S. E. (1995). "An overview of the toxicology of HFA-134a (1,1,1,2-tetrafluoroethane)". Hum. Exp. Toxicol. 14: 715–20.
  8. G. E. Millward, E. Tschuikow-Roux (1972). "Kinetic analysis of the shock wave decomposition of 1,1,1,2-tetrafluoroethane". 76 (3): 292–298. doi:10.1021/j100647a002.

External links

de:Tetrafluorethan



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