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

Abstract

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 19F 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 19F 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 19F 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.

Studies on the chemiexcitation step in peroxyoxalate chemiluminescence using steroid‐substituted activators

“…More direct experimental evidence was obtained by the study of the chemiluminescent properties of peracid intermediates involved in the peroxyoxalate sequence (21)(22)(23)(24)(25). However, the exact nature of the reactive intermediate involved and the mechanism of its interaction with the activator still remains to be clarified.…”

The chemiluminescent peroxyoxalate system: state of the art almost 50 years from its discovery

“…The reaction kinetics was studied using both, light emission intensity and absorption by produced phenol as parameters, and it was possible to attribute the faster rate constant of the rise in emission intensity ( In order to obtain a more precise insight into the reaction mechanism of the peroxyoxalate system, two research groups independently attempted the synthesis and study of peracid intermediates in the reaction sequence. Chokshi and coworkers 48 performed a 19 F NMR study on the reaction of bis(2,6-difluorophenyl)oxalate with hydrogen peroxide and concluded that the peracid derivative 11, should be an essential reactive intermediate in this transformation. Hohman and coworkers 49 , from the same research group, achieved the synthesis of silylprotected oxalic peracids 13 and 14 and studied their chemiluminescence properties, concluding that these compounds are involved in the reaction sequence leading to light emission.…”

Optimization of the Reaction Conditions for the Peroxyoxalate Chemiluminescence Detection System of Fluorescent Compounds in a High-Performance Liquid Chromatography

“…Givens et al 8 suggested that the hydroperoxy oxalate ester was the likely reactive intermediate based on an investigation with bis(2,6-difluorophenyl)oxalate (DFPO) using 19F-NMR.…”