Hexafluorobutadiene

Hexafluorobutadiene is an organofluorine compound with the formula (CF₂=CF)₂. A colorless gas, it has attracted attention as an etchant in microelectronics. It is the perfluoroanalogue of butadiene.

Hexafluorobutadiene

Names
Preferred IUPAC name Hexafluorobuta-1,3-diene
Other names 1,1,2,3,4,4-Hexafluoro-1,3-butadiene, FC 2316
Identifiers
CAS Number	685-63-2
3D model (JSmol)	Interactive image
ChemSpider	62837
ECHA InfoCard	100.010.620
EC Number	211-681-0
PubChem CID	69636
UNII	3KQJ9VP55Z Y
CompTox Dashboard (EPA)	DTXSID4060991
InChI InChI=1S/C4F6/c5-1(3(7)8)2(6)4(9)10 Key: LGPPATCNSOSOQH-UHFFFAOYSA-N
SMILES C(=C(F)F)(C(=C(F)F)F)F
Properties
Chemical formula	C4F6
Molar mass	162.034 g·mol−1
Appearance	colorless gas
Density	1.44 g/cm3 (@15 °C)
Melting point	−132 °C (−206 °F; 141 K)
Boiling point	6 °C (43 °F; 279 K)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220, H331
Precautionary statements	P210, P261, P271, P304+P340, P311, P321, P377, P381, P403, P403+P233, P405, P410+P403, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

It can be prepared by coupling of fluorinated C₂ precursors. Addition of iodine monochloride to chlorotrifluoroethylene gives iododichlorotrifluoroethane that can be coupled in the presence of mercury to give 1,2,3,4-tetrchlorohexafluorobutane:

2 CF₂Cl−CFCl(I) + Hg → CF₂Cl−CFCl−CFCl−CF₂Cl + HgI₂

Zn-induced dechlorination of this tetrachloride gives the desired perfluorinated diene:^[1]

CF₂Cl−CFCl−CFCl−CF₂Cl + 2 Zn → CF₂=CF−CF=CF₂ + 2 ZnCl₂

Reactions

The diene can be rehalogenated, e.g. with bromine upon UV irradiation:^[1]

CF₂=CF−CF=CF₂ + 2 Br₂ → CF₂Br−CFBr−CFBr−CF₂Br

Hexafluorobutadiene dimerizes via a [2+2] process at 150 °C to give perfluorinated divinylcyclobutanes.^[2]

In the presence of the strong Lewis acid aluminium chlorofluoride, hexafluorobutadiene isomerizes to hexafluoro-2-butyne:^[3]

CF₂=CFCF=CF₂ → CF₃C≡CCF₃

See also

• Hexafluorocyclobutene, an isomer of C₄F₆
• Hexachlorobutadiene