Perfluoroisobutene


Perfluoroisobutene 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.

Production and reactions

PFIB is one product of pyrolysis of polytetrafluoroethylene. Tetrafluoroethylene thermally dimerizes to octafluorocyclobutane, which above 600 °C 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 2CHCO2H, which readily decarboxylates to give hexafluoropropane.
Oxidation of HFIB with potassium permanganate gives hexafluoroacetone.

Safety

Perfluoroisobutene is highly toxic with an LCt = 880 mg⋅min⋅m−3. It is a Schedule 2 substance of the Chemical Weapons Convention. Its toxicity is comparable to that of phosgene.