Perfluoroisobutene (PFIB) is the perfluorocarbon with the formula . Classified as a perfluoroalkene, it is the fluorinated counterpart of the hydrocarbon isobutene. This colorless gas is notable for its high toxicity.
PFIB is one product of pyrolysis of polytetrafluoroethylene (PTFE). Tetrafluoroethylene thermally dimerizes to octafluorocyclobutane, which above 600 ðC degrades to hexafluoropropylene and PFIB.
Perfluoroisobutene is highly reactive toward nucleophiles, e.g. methanol. It also forms addition compounds with thiols, and it is this reactivity that may be related to its toxicity. It hydrolyzes readily to give the relatively innocuous (CF<sub>3</sub>)<sub>2</sub>CHCO<sub>2</sub>H, which readily decarboxylates to give hexafluoropropane.
Oxidation of HFIB with potassium permanganate gives hexafluoroacetone.
Perfluoroisobutene is highly toxic with an LCt = 880 mgâ minâ m<sup>âÂÂ3</sup> (mice). It is a Schedule 2 substance of the Chemical Weapons Convention. Its toxicity is comparable to that of phosgene.