Some reactions of polyfluorinated aryl radicals

Abstract

The thermal decomposition of perfluorobenzoyl peroxidein pentafluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,3,5-trifluorobenzene and 1,4-difluorobenzene has been investigated. A reaction scheme is proposed to account for the products of this reaction, which is also applicable to the thermal decomposition of benzoyl peroxide in polyfluoroaromatic solvents and of perfluorobenzoyl peroxide in aromatic hydrocarbon solvents.

It is suggested that when the aryl radical is of very different electronegativity from that of the solvent, it can be stabilised by formation of a pi-complex with the solvent. These pi-complexes can collapse into sigma-complexes, followed by their subsequent dimerisation and disproportionation.

It is also proposed that fluorinated sigma-complexes can be defluorinated by elimination of a molecule of hydrogen fluoride between a sigma-complex resulting from substitution at a fluorine bearing carbon atom and a hydrogen substituted sigma-complex.

The abstraction reactions of aryl radicals of the type resulting from the reactions of polyfluorinated anilines (p-XC₆F₄NH ₂, where X=F,H,MeO or Br) with amyl nitrite have been studied in polyhalogenomethane solvents and a possible explanation given for the yields of abstraction products obtained in these reactions.

The preparative usefulness of abstraction reactions by polyfluoroaryl radicals was investigated in the reactionsof pentafluoroaniline with amyl nitrite in the presence of curnene and also with methyl mercuric iodide and in the thermal decomposition of perfluorobenzoyl peroxide in sulphuryl chloride. Only the last reaction gives useful yields.

The reaction of pentafluoroaniline with amyl nitrite in the presence of iodobenzene indicated that iodine is possibly abstracted by the aryl radical from the solvent.