Photooxygenation of Chromone-2-carboxylic Acid: Identification of Ketohydroperoxide Using a Chemiluminescence Technique

Irradiation of chromone-2-carboxylic acid in aerated ethanol solution gives 4-hydroxycoumarine with the quantum yield of 0.02. The reaction proceeds via the decarboxylation followed by the addition of the oxygen molecule. Chemiluminescence measuring was successfully applied to detect the ketohydroperoxide intermediate in the photoreaction.