EXPERIMENTAL PROOF FOR THE INTERMEDIACY OF ZWITTERIONS IN THE PATHWAY LEADING TO LUMIKETONES UPON IRRADIATION OF 2,5-CYCLOHEXADIENONES

Article abstract of DOI:10.1016/S0040-4020(01)92381-6

Details are presented of kinetic studies, which demonstrate that a zwitterionic species is an obligatory intermediate in the photochemical rearrangement of a model 2,5-cyclohexadienone to its isomeric bicyclo<3.1.0>hex-3-en-2-one (lumiketone).In these studies, the zwitterionic intermediate has been succesfully intercepted by lithium chloride present in the mixture.In addition, studies of the temperature dependence of zwitterion-derived processes suggest that cycloreversion of the zwitterion to the starting dienone by a symmetryforbidden process in the main source of energy wastage in this system, and that this reversion becomes increasingly efficient as the temperature is raised.