Chemiluminescence of o-Dicarboxylic Acid Chlorides

According to this suggestion there exists an equilibrium between the normal six-membered ring phthaloylperoxide (24 a) and its phthalide isomer -analogous to that of the corresponding diacyl chlorides. 

The isomer can be readily isolated, and actually gives rise to chemiluminescence in the presence of Na202 and an appropriate fluorescer [27]. Dioxiranes and dioxiranone (29) have been described recently [28]. It is assumed that the isophthaloylperoxide (28) is transformed to phthalic anhydride by transfer of an oxygen atom to the fluorescer. 

Further investigations are necessary to confirm this very interesting new suggestion. 

The essential differences between the two forms of peroxide reaction can be seen in the following comparison  

With PPO and BPEA concentration = lxlO 0cLis ca. 2Ox0clDPO/BPEA in the same concentrations 

---