Screening for New Pathways in Atmospheric Oxidation Chemistry with Automated Mechanism Generation
Screening for New Pathways in Atmospheric Oxidation Chemistry with Automated Mechanism Generation
复制标题
利用自动机制生成筛选大气氧化化学新途径
DOI：
10.1021/acs.jpca.1c04297
复制
发表时间：
2021
期刊：
影响因子：
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通讯作者：
Kroll, Jesse H.
中科院分区：
文献类型：
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作者：
Barber, Victoria P.;Green, William H.;Kroll, Jesse H.
在地球大气层中，活性有机碳通过一个高度复杂的多代过程进行氧化，对空气质量和气候产生影响。几十年的实验和理论研究，主要是对碳氢化合物的反应，已经导致了有机化合物的气相氧化如何发生的规范理解。最近的研究揭示了一些例子，其中某些官能团的存在为关键的自由基中间体（包括烷基自由基、烷氧基自由基和过氧自由基）打开了反应途径，这些反应途径与传统的氧化机制有很大不同。这些发现突出了对系统地探索复杂的功能化分子的化学性质而又不过于昂贵的方法的需求。在这项工作中，自动化反应网络生成被用作筛选工具，在大气氧化化学的新途径。反应机理发生器（RMG）用于生成200种单、双官能团取代正戊烷的OH引发氧化反应网络。然后过滤所得到的网络，以突出关键自由基中间体的反应，这些反应足够快，可以与传统的大气去除过程以及与传统上接受的氧化机制不同的“非规范”过程竞争。几个最近报道的，不规范的大气机制出现在RMG数据集。这些“概念验证”结果为这种方法作为寻找被忽视的大气氧化化学的工具提供了信心。在数据集中也遇到了几种以前未报告的反应类型。其中最可能在大气中重要的是自由基-羰基闭环反应，其产生高度官能化的环状烷氧基自由基。该途径被认为是一个有前途的目标，通过实验和更详细的理论计算进行进一步研究。本文提出的方法代表了一种新的方式，有效地探索大气化学空间和发掘忽视的反应步骤，在大气氧化。
In the Earth’s atmosphere, reactive organic carbon undergoes oxidation via a highly complex, multigeneration process, with implications for air quality and climate. Decades of experimental and theoretical studies, primarily on the reactions of hydrocarbons, have led to a canonical understanding of how gas-phase oxidation of organic compounds takes place. Recent research has brought to light a number of examples where the presence of certain functional groups opens up reaction pathways for key radical intermediates, including alkyl radicals, alkoxy radicals, and peroxy radicals, that are substantially different from traditional oxidation mechanisms. These discoveries highlight the need for methods that systematically explore the chemistry of complex, functionalized molecules without being prohibitively expensive. In this work, automated reaction network generation is used as a screening tool for new pathways in atmospheric oxidation chemistry. The reaction mechanism generator (RMG) is used to generate reaction networks for the OH-initiated oxidation of 200 mono- and bifunctionally substitutedn-pentanes. The resulting networks are then filtered to highlight the reactions of key radical intermediates that are fast enough to compete with traditional atmospheric removal processes as well as “uncanonical” processes which differ from traditionally accepted oxidation mechanisms. Several recently reported, uncanonical atmospheric mechanisms appear in the RMG dataset. These “proof of concept” results provide confidence in this approach as a tool in the search for overlooked atmospheric oxidation chemistry. Several previously unreported reaction types are also encountered in the dataset. The most potentially atmospherically important of these is a radical–carbonyl ring-closure reaction that produces a highly functionalized cyclic alkoxy radical. This pathway is proposed as a promising target for further study via experiments and more detailed theoretical calculations. The approach presented herein represents a new way to efficiently explore atmospheric chemical space and unearth overlooked reaction steps in atmospheric oxidation.