Chemistry:Pentafluoroethane

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Pentafluoroethane
1,1,1,2,2-Pentafluoroethane-2D-skeletal.png
1,1,1,2,2-Pentafluoroethane.svg
Names
Preferred IUPAC name
Pentafluoroethane
Other names
Pentafluoroethane, Genetron HFC 125, Khladon 125, Suva 125, Freon 125, Fc-125, R-125
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 206-557-8
UNII
Properties
C2HF5
Molar mass 120.02 g/mol
Appearance Colourless gas. Has a faint, almost imperceptible odor
Density 1.53 g/cm3 (liquid at −48.5 °C)[1]
Melting point −103.0 °C (−153.4 °F; 170.2 K)
Boiling point −48.5 °C (−55.3 °F; 224.7 K)
Vapor pressure 1414.05 kPa (at 25 °C)
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):

Pentafluoroethane is a fluorocarbon with the formula CF3CHF2. Pentafluoroethane is currently used as a refrigerant (known as R-125) and also used as a fire suppression agent in fire suppression systems.

Pentafluoroethane does not deplete ozone so it has replaced earlier fluorinated chemicals that did. However while it has zero ozone depletion potential, it has high global warming potential, reported by the United States Environmental Protection Agency (EPA) as 3450 times that of carbon dioxide.[2]

Refrigerant

Shipping container for the gas, shown in Japan

Pentafluoroethane in a near azeotropic mixture with difluoromethane is known as R-410A, a common replacement for various chlorofluorocarbons (commonly known as Freon) in new refrigerant systems.

Fire suppression systems

HFC-125 (ECARO-25 / FE-25 / NAF S 125) is a gaseous fire suppression agent which can be used in clean agent fire suppression systems. In addition, HFC-125 leaves no residue on valuable equipment and material after discharge.[3] It is generally used in situations where water from a fire sprinkler would damage expensive equipment, or where water-based fire protection is impractical, such as museums, banks, clean rooms and hospitals. The HFC-125 clean agent is stored in a pressurized container and introduced into the hazard as a gas. The agent is odorless, colorless, electrically non-conductive, non-corrosive, and leaves no residue. It is used in occupied enclosed areas that contain high-value assets.

HFC-125 suppresses fire by absorbing heat energy at its molecular level faster than the heat can be generated, so the fire cannot sustain itself. It also forms free radicals to chemically interfere with the chain reaction of the combustion process. This makes it a highly effective fire fighting agent that is safe for people and causes no damage to equipment.

HFC-125 is considered a Clean Agent and is therefore included in the National Fire Protection Association's 2001 - Standard for Clean Agent Fire Extinguishing Systems.

Environmental impact

HFC-125 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.
Atmospheric concentration of pentafluoroethane at various latitudes since year 2007.

HFC-125 is a non-ozone depleting replacement for chlorine- or bromine-containing chemicals such as Halon 1301. Due to its global warming potential (GWP) of 3500 times that of CO₂ and atmospheric lifetime of 29 years, it is included in the list of controlled substances of the Montreal Protocol.[4][5]

When introduced to the market HFC-125 was not considered safe for use in occupied spaces. The US EPA Significant New Alternative Policy (SNAP) listing reflected this. Following the introduction and acceptance of the PBPK model in the NFPA standard 2001 on Clean Agent Fire Extinguishing Systems 2004 Edition, the restriction was relaxed and now HFC-125 can be used in occupied hazards. Generally, class B (flammable liquid) hazards require concentrations that exceed the agent's no-observed-adverse-effect level (NOAEL) so extra precautions must be taken to avoid prolonged exposure to the agent.

At high temperatures, pentafluoroethane will decompose and produce hydrogen fluoride. This is observable as presence of sharp, pungent odour, which can be perceived in concentrations far below a dangerous level. Other decomposition products include carbonyl fluoride, carbon monoxide and carbon dioxide. Prior to re-entry of a room where HFC-125 system has been activated to suppress a fire, the atmosphere should be tested. An Acid Scavenging Additive added to pentafluoroethane is able to reduce the amount of hydrogen fluoride.

Brands

ECARO-25 is a registered trademark of Fike Corporation. FE-25 is a registered trademark of E. I. du Pont de Nemours and Company or its affiliates. NAF S 125 (HFC-125 plus Acid Scavenging Additive) is a trademark of Safety Hi-Tech.

References

  1. ↑ Kirk-Othmer Encyclopedia of Chemical Technology. Wiley. ISBN 9780471238966. 
  2. ↑ "Protection of Stratospheric Ozone: Notice 20 for Significant New Alternatives Policy Program". Federal Register Environmental Documents. Environmental Protection Agency. March 29, 2006. http://www.epa.gov/EPA-AIR/2006/March/Day-29/a3030.htm. 
  3. ↑ "ECARO-25® Clean Agent Fire Suppression - HFC-125". http://www.fike.com/products/ecaro-25-clean-agent-fire-suppression-2/. 
  4. ↑ Montreal Protocol Section 1.1. including 2016 Kigali amendment (in effect in 2019)
  5. ↑ P. Forster; V. Ramaswamy; P. Artaxo; T. Berntsen; R. Betts; D.W. Fahey; J. Haywood; J. Lean et al. (2007). "Chapter 2: Changes in Atmospheric Constituents and in Radiative Forcing". in Solomon, S.; Miller, H.L.; Tignor, M. et al. (in en). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2.html. Retrieved 9 October 2016. 

External links



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