Hexafluoroethane is a perfluorocarbon (a completely fluorinated haloalkane) derived from ethane. It is a non-flammable gas negligibly soluble in water and slightly soluble in alcohol.

Physical properties

Hexafluoroethane's solid phase has two allotropes. 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:

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

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.

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

Environmental effects

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 10000 years and a global warming potential (GWP) of 9200. Atmospheric concentration of tetrafluoroethane is 3 pptv (increase by 3 pptv since 1750^[2]). 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

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.

References

See also

• Fluorocarbon, Perfluorocarbon
• Tetrafluoromethane
• Octafluoropropane
• Ethane
• Tetrafluoroethene
• Hexachloroethane

External links

• Purification process of hexafluoroethane
• Protocol for measurement of tetrafluoromethane and hexafluoroethane from primary aluminium production
• Ab initio vibrational analysis of hexafluoroethane C2F6
• Protocol for Measurement of Tetrafluoromethane (CF4) and Hexafluoroethane (C2F6) Emissions from Primary Aluminum Production
• Dynamics and structure of solid hexafluoroethane
• Thermochemistry data table at chemnet.ru