Hexafluoroethane

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Hexafluoroethane
Hexafluoroethane.png Hexafluoroethane-3D-balls.png
Identifiers
CAS number 76-16-4 YesY
PubChem 6431
ChemSpider 6191 YesY
EC number 200-939-8
ChEBI CHEBI:32905 YesY
ChEMBL CHEMBL116574 YesY
RTECS number KI4110000
Jmol-3D images Image 1
Properties
Molecular formula 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)
Solubility in water 0.0015%
log P 2
Vapor pressure 2.967 MPa at 20.1 °C

3.0701 MPa at 21 °C

kH 0.000058 mol.kg−1.bar−1
Hazards
MSDS External MSDS
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
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 (77 °F), 100 kPa)
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Infobox references

Hexafluoroethane is a fluorocarbon counterpart to the hydrocarbon ethane. It is a non-flammable gas negligibly soluble in water and slightly soluble in alcohol.

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]

Table of densities:

State, temperature Density (kg.m−3)
liquid, −78.2 °C 1608
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.

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

Environmental effects[edit]

Due to the high energy of C-F bonds, it is very inert and thus acts as an extremely stable greenhouse gas, with an atmospheric lifetime of 10,000 years (other sources: 500 years)[2] and a global warming potential (GWP) of 9200. A calculated atmospheric lifetime range of 500 to 10,000 years has been reported.[3] Atmospheric concentration of tetrafluoroethane is 3 pptv (increase by 3 pptv since 1750[4]). However, it has a strong absorption potential in the infrared part of the spectrum. Radiative forcing is 0.001 W/m2. Its ozone depletion potential (ODP) is 0.

Hexafluoroethane is listed in IPCC list of greenhouse gases.

Main industrial emissions of hexafluoroethane besides tetrafluoromethane are produced during production of aluminium using Hall-Héroult process.

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]

  • Bozin S E et al. (1968). "Growth of ionization currents in carbon tetrafluoride and hexafluoroethane". J. Phys. D: Appl. Phys. 1 (3): 327–334. doi:10.1088/0022-3727/1/3/309. 

External links[edit]