The reactions of oxygen atoms with some partially fluorinated olefins

Abstract

A detailed study was undertaken of the reaction of ground state oxygen atoms with the fluoroethylenes and with 14.32 trifluorobutene-1. Phe O(3P)/ fluorocethylene study yielded the following rate constants and Arrhenius parameters relative to ethylene. <table> Reactivity differences between the cis and trans isomers of 1,2 difluoroethylene have been attributed to a combination of entropic and enthalpic factors. . An attempt to relate reaction rates to various bond and atomic properties of the fluoroethylenes indicated that formation of a σ transition complex is probably the rate determining process. The reaction of ground state oxygen atoms with 1,1,2 trifluorobutene-1 yields 1 fiuoropropnee (cis and trans isomers) and carbonyl fluoride with quantum yields near to unity. Minor products identified included ethane, ethylene, propane, fluorocyclopropane and propionyl fluoride. In sharp contrast to the reactions of non-fluorinated olefins with oxygen atoms, epoxide formation was not significant in this system. The main primary process is thought to be formation of carbonyl fluoride and ethylfluorocarbene. CHZCHSCP:, fluorocyclopropane and 1 fluoropropene being products of the isomerisation of this carbene. Addition of oxygen to the system left the yield of 1 fluoropropene unchanged but greatly increased yields of propionyl and carbonyl fluoride. This behaviour has been attributed to the reaction of the biradical, CHZCH5CF-CP50°, with molecular oxygen to yield ultimately 1 fluoropropene, carbonyl fluoride and propionyl fluoride. The reaction schemes proposed satisfactorily explain major and minor product formation both in the presence and absence of molecular oxygen.