Mechanism and predictive model development of reaction rate constants for N-center radicals with O2. (December 2019)

• Record Type: Journal Article
• Authors: Liu, Cong; Ma, Fangfang; Elm, Jonas; Fu, Zihao; Tang, Weihao; Chen, Jingwen; Xie, Hong-Bin
• Is Part Of: Chemosphere. Volume 237(2019)
• Publication Date: 2019-12
• Subjects: N-Center radicals -- Reaction mechanism -- Reaction rate constants -- Quantitative structure-activity relationship; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.124411
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Atmospheric oxidation of NH x -containing ( x = 1, 2) compounds can produce N-center radicals, a precursor of toxic nitrosamines. The reaction rate constant ( k O2 ) with O2 has been considered as an important parameter to determine the nitrosamines yield in the subsequent reactions of N-center radicals. However, available k O2 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 k O2 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 k O2 values. Based on the mechanistic understanding of k O2 values, a quantitative structure-activity relationship (QSAR) model of k O2 values was developed. The model has satisfactory goodness-of-fit, robustness and predictive ability. The determined k O2 values and the in silico methods provide a scientific base for assessing formation risk of toxic nitrosamines in the atmosphere. Graphical abstract: Image 1 Highlights: Reaction mechanisms of 28 N-center radicals with O2 were revealed. Reaction rate constants ( k O2 ) of 28 N-center radicals with O2 were calculated. A high-throughput QSAR model was developed to predict k O2 values.