Reaction kinetics and mechanisms of neonicotinoidpesticides with sulfate radicals
作者:María L. Dell'Arciprete、Carlos J. Cobos、Daniel O. Mártire、Jorge P. Furlong、Mónica C. Gonzalez
DOI:10.1039/c0nj00726a
日期:——
The reaction kinetics and mechanisms of three neonicotinoid insecticides, imidacloprid (IMD), thiacloprid (THIA) and acetamiprid (ACT) with sulfate radicals were studied by flash-photolysis of peroxodisulfate, S2O82−. The absolute rate constants (3 ± 1) × 108, (1.1 ± 0.6) × 109, and (3 ± 1) × 109 M−1 s−1 were determined for IMD, ACT, and THIA, respectively. The reactivity and absorption spectra of the observed organic intermediates are in line with those reported for α-aminoalkyl radicals, and their absorption spectra agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. The mono- and di-hydroxylated oxidation products of the insecticides were identified as primary degradation products. The proposed reaction mechanism supports an initial charge transfer from the amidine nitrogen of the insecticides to the sulfate radicals. The pyridine moiety of the insecticides remains unaffected even after long irradiation times, until nicotinic acid is formed.
通过过二硫酸盐(S2O82-)的闪烁光解,研究了三种新烟碱类杀虫剂吡虫啉(IMD)、噻虫啉(THIA)和啶虫脒(ACT)与硫酸根自由基的反应动力学和机理。分别测定了 IMD、ACT 和 THIA 的绝对速率常数 (3 ± 1) × 108、(1.1 ± 0.6) × 109 和 (3 ± 1) × 109 M-1 s-1。所观察到的有机中间体的反应性和吸收光谱与所报道的 α-氨基烷基自由基的反应性和吸收光谱相一致,而且它们的吸收光谱与利用时间相关密度泛函理论估算的吸收光谱非常吻合,并明确考虑了体溶剂效应。杀虫剂的单羟基和二羟基氧化产物被确定为主要降解产物。所提出的反应机理支持从杀虫剂的脒氮到硫酸根自由基的初始电荷转移。即使经过长时间的辐照,杀虫剂的吡啶分子仍然不受影响,直到形成烟酸。