Photochemistry of halogenocarbon compounds. Part I. Rearrangement of pyridazines to pyrazines

Abstract

Vapour phase irradiation of tetrafluoropyridazine and various perfluoroalkylpyridazines using either medium or low pressure mercury lamps gives pyrazine derivatives. Substituents located 4,5- and 3,5- in the pyridazine occur at 2,5- and 2,6-positions respectively in the resulting pyrazine, and a mechanism to accommodate these specific substituent labelling results is advanced which involves intermediate valence isomers. Perfluoro-2,5- and -2,6-di-isopropylpyrazines are very slowly interconverted by irradiation in the liquid phase.