The photochemistry of hexafluoroacetylacetone in the vapour phase. Occurrence of a novel HF elimination reaction

Abstract

Abstract Photolysis of the vapour of hexafluoroacetylacetone HFAA in its enolic form involves decomposition by two independent primary processes, one of which is a novel elimination of HF giving 2,2‐difluoro‐2,3‐dihydro‐5‐trifluoromethylfuran‐3‐one: magnified image The HF is not vibrationally excited. Photolysis of the cyclic product of reaction (5) yields CF 2 radicals which, if HFAA is present, undergo an insertion into the enolic OH bond, magnified image The infrared, ultraviolet, nuclear magnetic resonance, and mass spectra of HFAA and of the products of reactions (5) and (6) have been measured. Approximate quantum yields for reactions (1) and (5) have been obtained. Both ϕ 1 and ϕ 5 depend on pressure and the ratio ϕ 1 /ϕ 5 increases with temperature and decreased wavelength of photolysing light. It is proposed that the ratio ϕ 1 /ϕ 5 increases as the vibrational energy of electronically excited HFAA increases.