Radical Additions to Fluoroolefins: Experimental Evidence for a Free-Radical Chain Mechanism in the Photo-Initiated Addition of Alcohols to Fluoroolefins

Abstract

Photo-initiated addition of 2-propanol to two fluoroolefinic compounds, i.e. methyl 2,4,4,5,6,6-hexafluoro-3-oxa-2-(trifluoromethyl)hex-5-enoate (IV) containing perfluoroallyloxy group and 8,9-dichloro-1,1,2,4,4,5,7,7,8,9,9-undecafluoro-3,6-dioxa-5-(t rifluoromethyl)dodec-1-ene (V) containing trifluorovinyloxy group were used to verify a free-radical chain mechanism by means of quantum yield measurements based on substrate-decay kinetic. UV-Light energy (254 nm) was transferred to the reaction system via triplet-excited acetone. Quantum yields Fi of the addition products (X, XI) reached values 68 and 42, respectively, and thus confirmed the chain mechanism. The olefinic compounds IV and V were synthesized on the basis of the reaction of 2,3-dichloro-2,3,3-trifluoropropanoyl fluoride (I) with hexafluoropropene-1,2-oxide. The photoaddition of 2-propanol to both olefins took place with complete regioselectivity.