Hexafluoroethane

Hexafluoroethane is an organofluorine compound with the chemical formula C₂F₆. It is a non-flammable colorless odorless gas negligibly soluble in water and slightly soluble in methanol. Its structure is F₃C−CF₃. It is an extremely potent and long-lived greenhouse gas. It is the perfluorocarbon counterpart to the hydrocarbon ethane.

Hexafluoroethane

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
CAS Number	76-16-4 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:32905 Y
ChEMBL	ChEMBL116574 Y
ChemSpider	6191 Y
ECHA InfoCard	100.000.855
EC Number	200-939-8
PubChem CID	6431
RTECS number	KI4110000
UNII	7VL5Z0IY3A Y
UN number	2193
CompTox Dashboard (EPA)	DTXSID2041915
InChI InChI=1S/C2F6/c3-1(4,5)2(6,7)8 Y Key: WMIYKQLTONQJES-UHFFFAOYSA-N Y 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	138.012 g·mol−1
Appearance	Colorless odorless gas
Density	5.734 kg/m3 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
Henry's law constant (kH)	0.000058 mol/(kg·bar)
Hazards
NFPA 704 (fire diamond)	1 0 0
Flash point	Non-flammable
Related compounds
Related compounds	Carbon tetrafluoride Octafluoropropane Ethane Difluoroacetylene Tetrafluoroethylene Tetrachloro-1,1-difluoroethane Tetrachloro-1,2-difluoroethane Tetrachloro-1,1-difluoroethane 1,1,2-Trichloro-1,2,2-trifluoroethane 1,1,1-Trichloro-2,2,2-trifluoroethane Pentachlorofluoroethane Hexachloroethane Hexabromoethane Hexaiodoethane
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). Y verify (what is YN ?) Infobox references

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] The critical point is at 19.89 °C (293.04 K) and 30.39 bar.^[2]

Table of densities:

State, temperature	Density (kg/m3)
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

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

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

Due to its high relative density, it gathers in low-lying areas, and at high concentrations it can cause asphyxiation.

See also

• Carbon tetrafluoride
• Octafluoropropane
• Tetrafluoroethene
• Hexachloroethane