1. Perfluoro-2-methyl-2-pentene reacts withα-oxides in the presence of CsF like perfluoroisobutylene. Olefins containing a perfluoro(dimethylpropyl)methyl group and cesium perfluoro-2-methyl-penten-3-olate are formed. 2. The reaction of perfluoro-2-methyl-2-pentene with epichlorohydrin in the presence of CsP results in the formation of trans-1,1,1,7,7,8,8,9,9,9-decafluoro-2,6,6-tris(trifluoromethyl)-4-nonene, 2-fluoro-2-pentafluoroethyl-3,3-bis(trifluoromethyl)-5-[α,α-(uhydro-β,β-bis(trifluoromethyl)perfluoroamyl] tetrahydrofuran, and 2-H-perfluoro-2-methylpentane. 3. The hexafluoropropylene dimer perfluoro-2-methyl-2-pentene is partially converted under the action of CsF into the thermodynamically most stable hexafluoropropylene trimer perfluoro-2,4-dimiethyl-3-heptene.