Glyphosate degradation has been extensively examined; however, only a few detailed computational studies have been performed on the topic so far. There are substantial differences between the degradation products of glyphosate, as AMPA (aminomethylphosphonic acid) is toxic while sarcosine intermediate is non-toxic. These species can have different effects on the environment and, indirectly, on the human body. We performed calculations using density functional theory and post-Hartree–Fock correlated ab initio methods to find the possible mechanisms for the degradation process by small (hydroxyl, peroxyl, and superoxide) radicals. We found that direct sarcosine formation is strongly dependent on the concentration of the radical species. AMPA and glycine were mostly formed as aldehyde derivatives, while in addition to the former, glyoxylate and bicarbonate are formed alternatively. A significant pH effect was also found for the competitive reactions determined by the calculated rate constants of the elementary steps. Overall barriers showed similarities by DFT but ab initio methods could separate them.

中文翻译：

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危险除草剂的归宿：基于 DFT 的草甘膦降解从头研究

草甘膦降解已被广泛研究；然而，到目前为止，仅对该主题进行了一些详细的计算研究。草甘膦的降解产物之间存在显着差异，因为 AMPA（氨基甲基膦酸）是有毒的，而肌氨酸中间体是无毒的。这些物种会对环境产生不同的影响，并间接地对人体产生影响。我们使用密度泛函理论和后 Hartree-Fock 相关ab initio 进行计算寻找小（羟基、过氧化氢和超氧化物）自由基降解过程的可能机制的方法。我们发现直接肌氨酸的形成强烈依赖于自由基种类的浓度。AMPA和甘氨酸大多以醛衍生物的形式形成，而除前者外，乙醛酸盐和碳酸氢盐也交替形成。对于由计算的基本步骤的速率常数确定的竞争反应，还发现了显着的 pH 值影响。总体障碍通过 DFT 显示出相似性，但从头开始的方法可以将它们分开。