Reactivity of neonicotinoid insecticides with carbonate radicals

Abstract

The reaction of three chloronicotinoid insecticides, namely Imidacloprid (IMD), Thiacloprid (THIA) and Acetamiprid (ACT), with carbonate radicals (CO3*-) was investigated. The second order rate constants (4 ± 1)×106, (2.8 ± 0.5)×105, and (1.5 ± 1)×105 M-1s-1 were determined for IMD, THIA and ACT, respectively. The absorption spectra of the organic intermediates formed after CO3*-attack -aminoalkyl radicals. A reaction mechanism involving an initial charge transfer from the amidine nitrogen of the insecticides to CO3*-is proposed and further supported by the identified reaction products. The pyridine moiety of the insecticides remains unaffected until nicotinic acid is formed. CO3*-radical reactivity towards IMD, ACT, and THIA is low compared to that of HO* radicals, excited triplet states, and 1O2, and is therefore little effective in depleting neonicotinoid insecticides. Dear Editor, Please find enclosed the manuscript entitled: "Removal of neonicotinoid insecticides by carbonate radicals". The present manuscript gives an insight into the reaction mechanisms and kinetics of carbonate radicals with neonicotinoid insecticides, namely imidacloprid, thiacloprid and acetamiprid. We thank you in advance for your kind cooperation. Cover Letter, For Editor only Highlights:Cloronicotinoid insecticides show low reactivity towards carbonate radicals.The reaction involves an initial charge transfer from the insecticide to CO 3 -.After prolonged irradiation chloronicotinic acid is formed.Hydroxyl and sulfate radicals are among the most effective in degrading the insecticides. 23The pyridine moiety of the insecticides remains unaffected until nicotinic acid is formed. 27

Photocatalytic, photolytic and radiolytic elimination of imidacloprid from aqueous solution: Reaction mechanism, efficiency and economic considerations

“…Dell'Arciprete et al [24,25] used SO4  and CO3  radical anions for imidacloprid (and two other neonicotinoids) oxidation, while Kosno et al [23] oxidized nicotine by N3  radicals.…”

Decomposition of atrazine by ionizing radiation: Kinetics, degradation pathways and influence of radical scavengers

“…Therefore, relatively higher produced. It has been reported that CO 3 ÅÀ is also highly reactive species with a redox potential of 1.78 V [35]. Since CO 3 ÅÀ is capable of oxidizing many organic pollutants efficiently, solutions containing CO 3 2À or HCO 3 À ions showed a less inhibitory impact on atrazine degradation.…”

Mechanistic study on thiacloprid transformation: Free radical reactions

“…Dell'Arciprete et al [14] reported that thiacloprid (and generally the chloronicotinoid insecticides) shows low reactivity towards carbonate radicals. Their reaction rate constants (k(THIA + • OH ) = 7.5 × 10 10 L mol -1 s -1 and k(THIA + CO 3…”

“…•− ) = 2.8 × 10 5 L mol -1 s -1 ) were obtained using flash photolysis, however, the former rate constant seems to be unrealistic, since it is half of an order of magnitude higher than the diffusion limited value [14,15].…”