A two-intermediate model for imidazole-promoted peroxyoxalate chemiluminescence

Abstract

A mechanism is proposed for imidazole-catalysed peroxyoxalate chemiluminescence. The reaction model includes a sequential formation of 1-aroxalylimidazole and 1,1'-oxalyldiimidazole as light-producing reaction intermediates. The suggestion is supported by the kinetic data obtained for the reaction of imidazole with bis(4-nitrophenyl) oxalate and on the recently reported ability of 1,1'-oxalyldiimidazole to function as an efficient chemiluminescence reagent. The relative contributions of different catalytic pathways and hydrolytic side-reactions are discussed.

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

“…These results suggested the initial formation of 1-aroxalylimidazole followed by formation of 1,1'-oxalyldiimidazolide (ODI, 10) as a second reactive intermediate, consistent with a general basecatalyzed nucleophilic attack of imidazole on the oxalic ester in the initial steps of the PO reaction (Scheme 6). 43 and outlined a mechanism similar to that proposed by Hadd and coworkers. 44,45 This mechanism involved a pre-equilibrium step with imidazole addition to the carbonyl group and formation of a zwitterionic tetrahedral intermediate and indicated similar reactivity for both oxalic esters groups.…”

Determination of Three Imidazole Derivatives by Flow-Injection Chemiluminescence

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General Acid and Base Catalysis by Phosphate in Peroxyoxalate Chemiluminescence

“…The high percentage of water allows the solubilization of hydrophilic analytes in potential analytical applications. Furthermore, PPO and an organic phosphate (TBAP) were chosen, since the first is more soluble in water than the others activators used for this reaction, [15,23,43] and the later permits to use higher concentrations without precipitating any species present in the reaction medium.…”

“…The singlet quantum yields determined for the kinetic assays with different TBAP concentration for the three oxalic esters are considerably lower than that reported in the literature for anhydrous organic media. [15,17,18,23,25] The peroxyoxalate system is known to reach singlet quantum yields of up to 60 %, [15] however, for TCPO in the binary DME/H 2 O 1:1(v/v) system, the F s obtained were in the order of magnitude of only 10 À5 E mol À1 (Table 3). For BMePO and BMPO, F s were even lower than that for TCPO, although with BMePO at pH = 8, the quantum yields also reached F s~1 0 À5 E mol À1 ( Table 6).…”