In search of a chemiluminescence 1,4-dioxy biradical.

Electron paramagnetic resonance spectroscopy has afforded the identification of a much postulated 1,4-dioxy biradical that occurs within the light producing pathway of peroxyoxalate chemiluminescence.

Studies on the mechanism of the peroxyoxalate chemiluminescence reaction: part 2. Further identification of intermediates using 2D EXSY 13C nuclear magnetic resonance spectroscopy.

Further consideration has been given to the reaction pathway of a model peroxyoxalate chemiluminescence system. Again utilising doubly labelled oxalyl chloride and anhydrous hydrogen peroxide, 2D EXSY (13)C nuclear magnetic resonance (NMR) spectroscopy experiments allowed for the characterisation of unknown products and key intermediate species on the dark side of the peroxyoxalate chemiluminescence reaction. Exchange spectroscopy afforded elucidation of a scheme comprised of two distinct mechanistic pathways, one of which contributes to chemiluminescence. (13)C NMR experiments carried out at varied reagent molar ratios demonstrated that excess amounts of hydrogen peroxide favoured formation of 1,2-dioxetanedione: the intermediate that, upon thermolysis, has been long thought to interact with a fluorophore to produce light.