INTERRELATIONSHIPS AMONG C6F10 VALENCE ISOMERS

Thermal and photochemical interconversions among the three valence iso mers perfluoro-1,5-hexadiene (1), perfluorobicyclo[2.2.0]hexane(2), an d perfluorobicyclo[2.1.1]hexane (3) have been explored. At 250-degrees -C 1 and 2 exist in equilibrium with K1-->2 = 1.1, but at higher tempe ratures irreversible isomerization to 3 becomes rapid. This chemistry contrasts sharply with the behavior of the corresponding hydrocarbons, where the diene is lowest in free energy. Mercury-sensitized photolys is of diene 1 yields 3 and 2 in ratios of 3-4:1. The cleanness of both the thermal and the photochemistry, together with thermodynamics favo rable to cyclization, bode well for synthesizing new bicyclic and poly cyclic fluorocarbons from other unsaturated precursors.