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Hexafluoroethane

Summary

Hexafluoroethane is the perfluorocarbon counterpart to the hydrocarbon ethane. It is a non-flammable gas negligibly soluble in water and slightly soluble in methanol. It is an extremely potent and long-lived greenhouse gas.

Hexafluoroethane
Structural formula of hexafluoroethane
Ball-and-stick model of the hexafluoroethane molecule
Names
Preferred IUPAC name
Hexafluoroethane
Other names
Carbon hexafluoride, 1,1,1,2,2,2-Hexafluoroethane, Perfluoroethane, Ethforane, Halocarbon 116, PFC-116, CFC-116, R-116, Arcton 116, Halon 2600, UN 2193
Identifiers
  • 76-16-4 checkY
3D model (JSmol)
  • Interactive image
ChEBI
  • CHEBI:32905 checkY
ChEMBL
  • ChEMBL116574 checkY
ChemSpider
  • 6191 checkY
ECHA InfoCard 100.000.855 Edit this at Wikidata
EC Number
  • 200-939-8
  • 6431
RTECS number
  • KI4110000
UNII
  • 7VL5Z0IY3A checkY
UN number 2193
  • DTXSID2041915 Edit this at Wikidata
  • InChI=1S/C2F6/c3-1(4,5)2(6,7)8 checkY
    Key: WMIYKQLTONQJES-UHFFFAOYSA-N checkY
  • InChI=1/C2F6/c3-1(4,5)2(6,7)8
    Key: WMIYKQLTONQJES-UHFFFAOYAP
  • FC(F)(F)C(F)(F)F
Properties
C2F6
Molar mass 138.01 g.mol−1
Appearance Colorless odorless gas
Density 5.734 kg.m−3 at 24 °C
Melting point −100.6 °C (−149.1 °F; 172.6 K)
Boiling point −78.2 °C (−108.8 °F; 195.0 K)
0.0015%
log P 2
0.000058 mol.kg−1.bar−1
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Flash point Non-flammable
Supplementary data page
Hexafluoroethane (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

Physical properties edit

Hexafluoroethane's solid phase has two polymorphs. In the scientific literature, different phase transition temperatures have been stated. The latest works assign it at 103 K (−170 °C). Below 103 K it has a slightly disordered structure, and over the transition point, it has a body centered cubic structure.[1] The critical point is at 19.89 °C (293.04 K) and 30.39 bar.[2]

Table of densities:

State, temperature Density (kg.m−3)
liquid, −78.2 °C 16.08
gas, −78.2 °C 8.86
gas, 15 °C 5.84
gas, 20.1 °C 5.716
gas, 24 °C 5.734

Vapor density is 4.823 (air = 1), specific gravity at 21 °C is 4.773 (air = 1) and specific volume at 21 °C is 0.1748 m3/kg.

Uses edit

Hexafluoroethane is used as a versatile etchant in semiconductor manufacturing. It can be used for selective etching of metal silicides and oxides versus their metal substrates and also for etching of silicon dioxide over silicon. The primary aluminium and the semiconductor manufacturing industries are the major emitters of hexafluoroethane using the Hall-Héroult process.

Together with trifluoromethane it is used in refrigerants R508A (61%) and R508B (54%).

It is used as a tamponade to assist in retinal reattachment following vitreoretinal surgery.[3]

Environmental effects edit

 
Hexafluoroethane timeseries at various latitudes.
 
PFC-116 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.

Due to the high energy of C−F bonds, hexafluoroethane is nearly inert and thus acts as an extremely stable greenhouse gas, with an atmospheric lifetime of 10,000 years (other sources: 500 years).[4] It has a global warming potential (GWP) of 9200 and an ozone depletion potential (ODP) of 0. Hexafluoroethane is included in the IPCC list of greenhouse gases.

Hexafluoroethane did not exist in significant amounts in the environment prior to industrial-scale manufacturing. Atmospheric concentration of hexafluoroethane reached 3 pptv at the start of the 21st century.[5] Its absorption bands in the infrared part of the spectrum cause a radiative forcing of about 0.001 W/m2.

Health risks edit

Due to its high relative density, it gathers in low-lying areas, and at high concentrations it can cause asphyxiation. Other health effects are similar to tetrafluoromethane.

See also edit

References edit

  1. ^ Zeng, S.X.; Simmons, R.O.; Timms, D.N.; Evans, A.C. (1999). "Dynamics and structure of solid hexafluoroethane". Journal of Chemical Physics. 110 (3): 1650–61. Bibcode:1999JChPh.110.1650Z. doi:10.1063/1.477806.
  2. ^ Helmut Schan: Handbuch der reinsten Gase. Springer, 2005, ISBN 978-3-540-23215-5, S. 307.
  3. ^ Andreas Kontos; James Tee; Alastair Stuart; Zaid Shalchi; Tom H Williamson (2016). "Duration of intraocular gases following vitreoretinal surgery". Graefes Arch Clin Exp Ophthalmol. 255 (2): 231–236. doi:10.1007/s00417-016-3438-3. PMID 27460279. S2CID 23629379.
  4. ^ "Perfluoroethane CASRN: 76-16-4". TOXNET Toxicology Data Network. National Library of Medicine. 2016-10-25.
  5. ^ "Climate Change 2001: The Scientific Basis". Archived from the original on 2007-06-15. Retrieved 2007-06-02.
  • Bozin SE, et al. (1968). "Growth of ionization currents in carbon tetrafluoride and hexafluoroethane". J. Phys. D: Appl. Phys. 1 (3): 327–334. Bibcode:1968JPhD....1..327B. doi:10.1088/0022-3727/1/3/309. S2CID 250891553.

External links edit

  • Purification process of hexafluoroethane
  • Protocol for measurement of tetrafluoromethane and hexafluoroethane from primary aluminium production
  • De Maré, G.R.; Panchenko, Yu. N. (March 2006). "Ab initio vibrational analysis of hexafluoroethane C2F6". Journal of Structural Chemistry. 47 (2): 232–240. doi:10.1007/s10947-006-0291-y. S2CID 96363970.
  • Protocol for Measurement of Tetrafluoromethane (CF
    4    ) and Hexafluoroethane (C
    2    F
    6    ) Emissions from Primary Aluminum Production
  • Thermochemistry data table at chemnet.ru

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