Mechanistic study on thiacloprid transformation: Free radical reactions

Abstract

Highlights  • OH/eaqexhibits appreciable reactivity towards the insecticide thiacloprid  The majority of • OH attack the key cyanoiminothiazolidine pharmacophore  α-aminoalkyl, N-centred, α-(alkylthio)alkyl and >S •-OH radicals form on this moiety  One-electron reduction occurs at the pyridyl function yielding pyridinyl radicals  Destruction of pharmacologically important substructures is anticipated

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

“…In the spectrum there is a well-resolved strong absorbance at 330 nm and two other bands at ~525 nm and 250 nm. For imidacloprid these spectral characteristics, the places of absorption bands and the intensities are similar to the characteristics of the spectrum of the transient(s) detected in the  OH + thiacloprid reaction [22]. At the same time, both spectra are similar to the spectrum characterizing the  OH + nicotine system published by Kosno et al [23], with max at 330 nm and at 470 nm.…”

“…3, Inset) supplied a second order rate constant of (6.97±0.54)  10 9 mol −1 dm 3 s −1 . This rate constant is higher than that measured for thiacloprid (4.8  10 9 mol −1 dm 3 s −1 [22]) in the same laboratory with the same technique, but it agrees with the value determined for nicotine (6.7  10 9 mol −1 dm 3 s −1 [23]) using also pulse radiolysis technique.…”

“…Beside HCH radicals ferricyanide ions may also react with several other radical species, including benzyl radicals and -aminoalkyl radicals (Fig. 4, 2-4) [22]. These radicals can form in the  OH + imidacloprid reaction by hydrogen atom elimination from the CH2 units.…”

“…Hydroxylated pyridine ring containing products forming in the  OH + imidacloprid reactions were not described in the literature [26,28] either.  OH addition to the aromatic ring with low yield was suggested in the case of thiacloprid [22,33].…”

“…OH addition to the aromatic ring, transforming them to phenol type molecules[22]. HCH radicals formed from aromatic molecules have wide absorption bands with maxima between 300-400 nm and molar absorbances of 3000-6000 mol 1 dm 3 cm 1 .…”