Hexafluoroethane

Hexafluoroethane
Names
	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
CAS Number	76-16-4 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:32905 ;
ChEMBL	ChEMBL116574 ;
ChemSpider	6191 ;
ECHA InfoCard	100.000.855
EC Number	200-939-8;
PubChem CID	6431;
RTECS number	KI4110000;
CompTox Dashboard (EPA)	DTXSID2041915 ;
	InChI InChI=1S/C2F6/c3-1(4,5)2(6,7)8 Key: WMIYKQLTONQJES-UHFFFAOYSA-N ; InChI=1/C2F6/c3-1(4,5)2(6,7)8 Key: WMIYKQLTONQJES-UHFFFAOYAP;
	SMILES FC(F)(F)C(F)(F)F;
Properties
Chemical 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
Henry's law; constant (kH)	0.000058 mol.kg−1.bar−1
Hazards
NFPA 704 (fire diamond)	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). verify (what is ?) 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

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

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

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

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

Bozin SE, 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

[1] Dynamics and structure of solid hexafluoroethane

[2] [1]

[3] :Toxnet, US government

[4] Climate Change 2001: The Scientific Basis

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