Oxalate/hydrogen peroxide chemiluminescence reaction. A 19 F NMR probe of the reaction mechanism

The mechanism of the oxalate/hydrogen peroxide chemiluminescence reaction has been examined by magnetic resonance techniques. Investigation of the reactive intermediates involved in chemiluminescence was carried out with bis(2,6‐difluorophenyl)oxalate (DFPO) using 19 F NMR to probe its reactions with aqueous hydrogen peroxide. Formation and reactions of the intermediate hydroperoxy oxalate ester B along with the formation of the half ester product C and difluorophenol D were monitored by 19 F NMR. When the reaction of DFPO and aqueous hydrogen peroxide was carried out in the presence of dansylphenylalanine, a typical fluorescent analyte, the intensity of the resonance due to the intermediate B was diminished in direct proportion to the concentration of the analyte. Comparison of the time/intensity profile of the chemiluminescence emission with that of the 19 F NMR transient suggests that the hydroperoxy oxalate ester B is the likely ‘reactive’ intermediate, capable of participating in a chemically initiated electron exchange luminescence mechanism.