Bresnahan Caitlin G, McAlexander Harley R, Woodley Christa M, Shukla Manoj K
Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee, USA.
US Army Corps of Engineers, Engineer Research and Development Center, Environmental Laboratory, Vicksburg 39180, Mississippi, USA.
Environ Sci Process Impacts. 2022 Dec 14;24(12):2249-2262. doi: 10.1039/d2em00296e.
Parathion, a once commonly used pesticide known for its potential toxicity, can follow several degradation mechanisms in the environment. Given the species stability and persistence, parathion can be washed into waterways from rain, and therefore an atomistic perspective of the hydrolysis of parathion, and its byproduct paraoxon, is required in order to understand its fate in the environment. Experimental studies have determined that pH plays an important role in the calculated hydrolysis rate constants of parathion degradation. In this work, the degradation of parathion into either paraoxon or 4-nitrophenol, and the degradation of paraoxon to 4-nitrophenol are explored through density functional theory using the M06-2X functional. How the level of basicity affects the reaction mechanism is explored through two different hydroxide/water environments. Our calculations support the anticipated mechanisms determined by previous experimental work that the formation of 4-nitrophenol is the predominant pathway in hydrolysis of parathion.
对硫磷是一种曾被广泛使用的具有潜在毒性的杀虫剂，在环境中可通过多种降解机制进行降解。鉴于该物质的稳定性和持久性，对硫磷可随雨水冲刷进入水体，因此，为了解其在环境中的归宿，需要从原子层面研究对硫磷及其副产物对氧磷的水解过程。实验研究表明，pH值在对硫磷降解的水解速率常数计算中起着重要作用。在本研究中，我们采用M06-2X泛函，通过密度泛函理论研究了对硫磷降解为对氧磷或4-硝基苯酚的过程，以及对氧磷降解为4-硝基苯酚的过程。通过两种不同的氢氧化物/水环境，探讨了碱度水平对反应机理的影响。我们的计算结果支持了先前实验工作所确定的预期机理，即4-硝基苯酚的形成是对硫磷水解的主要途径。
