M. Napoli, A. Scipioni, C. Fraccaro
Aug 1, 1992
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Journal
Journal of Fluorine Chemistry
Abstract
Abstract The current industrial technique for perfluorooctanoic acid production (a precursor of important emulsifying agents for polymerizations) is the electrochemical fluorination of n-octanoyl fluoride in anhydrous HF (Simons process). This process suffers from a poor molar yield of perfluorooctanoyl fluoride (15–20%), due to formation of large amounts of several by-products. F -2- butyl-tetrahydrofuran and F -2-propyl-tetrahydropyran are two of these by- products [A.K. Barbour, in R.E. Banks (ed.), Organofluorine Chemicals and Their Industrial Applications , (1979) 56], whose formation arises from cyclization of the carbonyl oxygen on the carbon atoms 4 or 5 of the linear hydrogenated chain respectively [F.G. Drakesmith and D.A. Hughes, J. Appl. Electrochem. , 9 (1979) 685]. On the basis of the mechanism EC b EC N proposed for this process [J. Burdon, I.W. Parsons and J.C. Tatlow, Tetrahedron , 28 (1972) 43; I.N. Rozhkov , Russian Chem. Rev., 45 (1976) 615], the possibility to reduce significantly this cyclization was confirmed by starting from precursors having the positions 4 and 5 fully fluorinated; in fact, by using 4,4-difluorooctanoyl fluoride [ UK Pat. 1 000 288 (1965)]* or 4-perfluorobutyl-butanoyl fluoride [M. Napoli, L. Conte, G.P. Gambaretto and F.M. Carlini, J. Fluorine Chem., 45 (1989) 213]* as a starting material, a yield decrease of F-2-butyl-tetrahydrofuran or F-2-propyl-tetrahydropyran was observed, so that an improved molar yield of perfluorooctanoyl fluoride was experimentally detected. The results obtained when a new fluorinated compound (2-perfluorohexyl acetic acid) was used as a starting material in the electrofluorination process are presented here and the yields compared with those observed in the above-cited references (*).