perfluoroisobutene perfluoroisobutene perfluoroisobutene (pfib) is the perfluorocarbon counterpart of the hydrocarbon isobutene and has the formula (cf3)2c=cf2. an alkene, it is a colorless gas that is notable as a highly toxic perfluoroalkene. few simple alkenes are as toxic. perfluoroisobutene names preferred iupac name 1,1,3,3,3-pentafluoro-2-(trifluoromethyl)prop-1-ene other names perfluoroisobutene, perfluoroisobutylene, octafluoroisobutylene, octafluoro-sec-butene, pfib identifiers cas number 382-21-8 y 3d model (jsmol) interactive image chembl chembl4634291 chemspider 55060 y echa infocard 100.108.743 ec number 609-533-9 pubchem cid 61109 rtecs number ud1800000 unii 1j9bgs6nty y comptox dashboard (epa) dtxsid4073176 inchi inchi=1s/c4f8/c5-2(6)1(3(7,8)9)4(10,11)12 nkey: dafibnsjxigbqb-uhfffaoysa-n ninchi=1/c4f8/c5-2(6)1(3(7,8)9)4(10,11)12key: dafibnsjxigbqb-uhfffaoyaf smiles c(=c(f)f)(c(f)(f)f)c(f)(f)f properties chemical formula c4f8 molar mass 200.030 g/mol appearance colorless gas density 8.2 g/l melting point −130 °c (−202 °f; 143 k) boiling point 7.0 °c (44.6 °f; 280.1 k) hazards ghs labelling: pictograms signal word danger hazard statements h330, h370 precautionary statements p260, p264, p270, p271, p284, p304+p340, p307+p311, p310, p320, p321, p403+p233, p405, p501 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). n verify (what is yn ?) infobox references safety perfluoroisobutene is highly toxic with an lct = 880 mg⋅min⋅m−3 (mice). it is a schedule 2 substance of the chemical weapons convention. perfluoroisobutene is highly reactive toward nucleophiles. it hydrolyzes readily to give the relatively innocuous (cf3)2chco2h, which readily decarboxylates to give hexafluoropropane. it forms addition compounds with thiols, and it is this reactivity that may be related to its toxicity. pfib is a product of pyrolysis of polytetrafluoroethylene (ptfe), one of the substances invoked to explain polymer fume fever.