Hexafluoro-2-butyne

Hexafluoro-2-butyne is a fluorocarbon with the chemical structure CF₃C≡CCF₃. HFB is a particularly electrophilic acetylene derivative, and hence a potent dienophile for Diels–Alder reactions.

Synthesis and reactions

HFB is prepared by the action of sulfur tetrafluoride on acetylenedicarboxylic acid or by the reaction of potassium fluoride with hexachlorobutadiene.
In the presence of the strong Lewis acid aluminium chlorofluoride, hexafluorobutadiene isomerizes to HFB:
HFB reacts with sulfur to give 3,4-bis(trifluoromethyl)-1,2-dithiete.
Cycloaddition of HFB and dithionitronium gives the 1,2,5-dithiazolium cation. This derivative can be reduced to the 7 electron neutral radical. This particular 1,3,5-dithiazole is also rare example of a radical that can be obtained as solid, liquid, and gaseous states. As a gas, it is blue.
As an electrophilic alkyne, HFB forms a variety of alkyne complexes by reaction with low-valent metal complexes.