Chem. Soc., 67, 1906 (1945). contact time over CsF 22y0 CF3C= CCF3 and 4oy0 CFz= CFCF= CF2 were recovered. Recently, Christie, Tlumac, Dresdner and Young reported the preparation of perfluorobicyclopentane, bp 3.3-3.6, 7 from perfluoro-l, 4-pentadiene by passing the diene over cesium fluoride at 250. 6 On repeating this reaction we find that the product, obtained in about 95% yield and purity with a 40 sec. contact time, is, in fact, ...