N中心自由基与O2反应速率常数的机理和预测模型的建立。,Chemosphere

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N中心自由基与O2反应速率常数的机理和预测模型的建立。
Chemosphere ( IF 8.1 ) Pub Date : 2019-08-06 , DOI: 10.1016/j.chemosphere.2019.124411
Cong Liu ₁ , Fangfang Ma ₁ , Jonas Elm ₂ , Zihao Fu ₁ , Weihao Tang ₁ , Jingwen Chen ₁ , Hong-Bin Xie ₁

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含NHx（x = 1，2）化合物的大气氧化可产生N-中心自由基，这是有毒亚硝胺的前体。与O2的反应速率常数（kO2）被认为是确定N中心自由基后续反应中亚硝胺收率的重要参数。但是，N中心自由基的可用kO2值受到限制。在此，采用三步方案，包括对28个不同N中心自由基与O2的反应进行机理分析和动力学计算，并采取了模型开发方法来解决kO2数据不足的问题。主要使用的工具包括成本高昂的耦合聚类理论（CCSD（T）），动力学模型和统计数据。结果表明，直接的H吸收途径最适合所有N中心自由基与O2的反应。N中心自由基的特定分子构象和CH键能是确定kO2值的两个重要因素。基于对kO2值的机械理解，建立了kO2值的定量构效关系（QSAR）模型。该模型具有令人满意的拟合优度，鲁棒性和预测能力。确定的kO2值和计算机方法可为评估大气中有毒亚硝胺的形成风险提供科学依据。

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Mechanism and predictive model development of reaction rate constants for N-center radicals with O2.

Atmospheric oxidation of NHx-containing (x = 1, 2) compounds can produce N-center radicals, a precursor of toxic nitrosamines. The reaction rate constant (kO2) with O2 has been considered as an important parameter to determine the nitrosamines yield in the subsequent reactions of N-center radicals. However, available kO2 values of N-center radicals are limited. Here, a three-step scheme including mechanistic analysis and kinetics calculation of the reactions of 28 various N-center radicals with O2, and model development was taken to solve the kO2 data shortage. Mainly employed tools include highly cost-expensive coupled-cluster theory (CCSD(T)), kinetic model and statistics. The results indicate that the direct H-abstraction pathway is the most favorable for the reactions of all considered N-center radicals with O2. The specific molecular conformation and the C-H bond energy of the N-center radicals are two important factors to determine kO2 values. Based on the mechanistic understanding of kO2 values, a quantitative structure-activity relationship (QSAR) model of kO2 values was developed. The model has satisfactory goodness-of-fit, robustness and predictive ability. The determined kO2 values and the in silico methods provide a scientific base for assessing formation risk of toxic nitrosamines in the atmosphere.

更新日期：2019-08-06

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