Fluoride ion-induced reaction of tetrafluoroethylene with pentafluoropyridine gave perfluoro-4-ethyl, -2,4-diethyl-, and -2,4,5-triethyl-pyridines. The trisubstituted product could not be rearranged, in the presence of fluoride ion at elevated temperatures, to the -2,4,6-isomer. Related studies with perfluoroethylisopropylpyridines indicated that ease of rearrangement of -2,4,5- to -2,4,6-isomers is limited by the stability of the migrating anion. Reaction of tetrafluoroethylene with tetrafluoropyridazine gave perfluoro-4-ethyl-, -4,5-diethyl-, and -3,4,5-triethyl-pyridazines, in low yields, as well as high molecular weight oils. The formation of these oils is attributed to an electron-transfer process.