Perfluorination of Allene Derivatives by Direct Fluorination
Perfluoropropane was prepared from allene with elemental fluorine in the presence of sodium fluoride in 84percent yield for the first time.The reaction of allene with elemental fluorine afforded 2,2-difluoropropane in the absence of sodium fluoride.Methoxyallene and cyanoallene were perfluorinated with elemental fluorine in the presence of sodium fluoride to give heptafluoropropyl trifluoromethyl ether and heptafluoropropyl cyanide in good yields respectively.In addition, the direct fluorination of cyanoallene in the presence of cesium fluoride afforded N,N-difluorononafluorobutylamine in 95percent yield.
Fluorination of Alkanes by Chlorine Trifluoride. Hydride Abstraction Mechanism
Addition of chlorine trifluoride to a solution of alkane in Freon or liquid carbon dioxide at -75 deg C gives good yields of monofluoroalkane along with difluoro- and trifluoroalkanes in amounts dependent on reactant proportions.The inorganic products are HF and ClF.The reaction is highly selective for 3 over 2 positions.Methane and hexamethylethane are unreactive.Neohexane fluorinates with rearrangement, but 2-fluoro-3,3-dimethylbutane exposed to the postreaction medium does not rearrange.A hydride abstraction mechanism is inferred.