Kinetic studies on the peroxyoxalate chemiluminescence reaction: determination of the cyclization rate constant

Abstract

Although more currently utilized as analytical tool because of its high sensitivity and good reproducibility, the mechanism of the peroxyoxalate system, a chemiluminescence reaction with quantum yields only comparable to bioluminescence systems, has been extensively studied. The light emission mechanism can be divided in the pathway before chemiexcitation, which contains the rate-limiting steps, and the fast and kinetically non-observable chemiexcitation step. In this work, we obtain information on the mechanism of the slow pathways, attribute values to several rate constants prior to chemiexcitation and suggest a mechanistic scheme that could help optimization of conditions when the peroxyoxalate reaction is used as analytical tool.

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

“…Mechanistic proposal for the chemiluminescence of the peroxyoxalate system, as suggested by Stevani et al 37 In a subsequent work on this system, da Silva and coworkers 47 were able to suggest a complete reaction sequence for the imidazole-catalyzed PO reaction which could explain the observed light-emission profile, consisting of an initial rapid increase of the emission intensity, followed by a slower decay ( Figure 3). 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.…”

Practical Chemical Kinetics in Solution

“…An important example of a complex chemiluminescent transformation, with various consecutive and parallel reaction steps, is the base-catalyzed reaction of aromatic oxalic esters with hydrogen peroxide [52,[94][95][96][97][98][99][100][101][102][103][104][105]. This reaction illustrates how rate constants of a multistep complex reaction can be determined from kinetic experiment.…”

Luz: um raro produto de reação

“…27 Em trabalhos publicados por Rauhut et al, foi proposto pela primeira vez um mecanismo para a reação peróxi-oxalato, 100-102 onde se postulou a formação de um intermediário de alta energia (IAE) a partir da reação de ésteres oxálicos com peróxido de hidrogênio que, por meio do mecanismo CIEEL, leva à formação do ACT no estado excitado. A cinética das reações anteriores à formação do IAE, no sistema peróxi-oxalato, foi estudada com mais detalhes [100][101][102][103] ; com base na determinação de constantes de velocidade para tal sistema foi proposto, por Stevani et al, um esquema mecanístico simplificado (Esquema 7), 104,105 mais especificamente, para a reação de oxalato de bis(2,4,6-triclorofenila) com H 2 O 2 , catalisada por IMI-H. Nesses trabalhos, comprovou-se o papel de IMI-H como catalisador nucleofílico, através das evidências obtidas da formação do intermediário de reação 1,1'-oxalildi-imidazolídico.…”