Ozonolysis of unsaturated perfluorocompounds: Anomalous behavior of substrates

An unusual cooxidation of CF 3 COOH and perfluoroalkenes by ozone has been discovered. Ozonolysis of perfluorooctene-1 (1) and trans-perfluorooctene-2 ( 2 ) with O 2 /O 3 mixture at -18-0°C gives rise to fluoroanhydrides of corresponding perfluorocarboxylic acids in yields of 80-100%. Peroxytrifluoroacetic acid (CF 3 COOOH) was found to be formed in amounts commensurate with those of fluoranhydrides. Thus the reaction could be described by equation: R 1 f CF=CFR 2 f + CF 3 COOH + O 3 → R 1 f COF + R 2 f COF + CF 3 COOOH (1) No reaction between CF 3 COOH and O 3 was observed in the absence of perfluoroalkenes. Perfluorobenzene C 6 F 6 also undergoes the ozonolysis in CF 3 COOH solutions. The reactivity of the substrates under investigation diminishes in a sequence: 2 > 1 >C 6 F 6 ⋙ cyclo-C 6 F 10 revealing the inversion of activity of internal and terminal perfluoroalkenes usually observed in oxidation reactions The reaction (1) was not affected by the presence of HClO 4 or SbF 5 additives. Thus species of type HO + 3 seemingly do not take part in the reaction (1). All the facts available could be explained in the framework of a mechanism including intermediate formation of tetroxide CF 3 COOOOOH ( 3 ) through action of CF 3 COOH with O 3 . The transfer of O 2 (presumably in 1 O 2 form) from 3 to the substrate is considered to be a step leading to the oxidation products. In this context the anomalous low reactivity of cyclo-C 6 F 10 could be explained in terms of the Woodward-Hoffmann rules.