Excited state, formation from dioxetans

V.5 Mechanism of Excited State Formation from Dioxetans... 

In this part of the chapter, we will briefly outline the main types of CL reactions which can be functionally classified by the nature of the excitation process that leads to the formation of the electronically excited state of the light-emitting species. Direct chemiluminescence is the term employed for a reaction in which the excited product is formed directly from the unimolecular reaction of a high-energy intermediate that has been formed in prior reaction steps. The simplest example of this type of CL is the unimolecular decomposition of 1,2-dioxetanes, which are isolated HEI. Thermal decomposition of 1,2-dioxetanes leads mainly to the formation of triplet-excited carbonyl compounds. Although singlet-excited carbonyl compounds are produced in much lower yields, their fluorescence emission constitutes the direct chemiluminescence emission observed in these transformations under normal conditions in aerated solutions ... 

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