Atmospheric reactions of glyoxal with NO2 and NH2 radicals: Hydrogen abstraction mechanism and natural bond orbital analysis

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
H. Saghafi, M. Vahedpour
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引用次数: 4

Abstract

Glyoxal can be important in atmospheric chemistry in terms of its ability to convert to secondary organic aerosols. In this study, the glyoxal-breaking reaction by two atmospheric active radicals, NO2 and NH2, has been investigated at the B3LYP and M06-2X levels in connection with 6-311++G(d,p) basis set. The formation of the most stable adducts from glyoxal with NO2/NH2 radical requires two hydrogen atom transfers. The accuracy of the predicted mechanisms in describing the hydrogen transfers was confirmed by atoms-in-molecules calculations and natural bond orbital analysis. The calculated results predict that hydrogen transfer process in both reactions at the M06-2X level is favourable from the kinetic and thermodynamic points of view. In the natural bond orbital analysis, the stabilization energy, E(2), delocalization corrections, at the B3LYP level is much higher than the same results at the M06-2X level (nearly twice). The activation thermodynamic parameters show that the first steps of the two reactions have lower barrier energy than the second steps. The Gibbs free energy values estimate that adducts of both the reactions at the mentioned method are spontaneous. The whole reaction of glyoxal + NH2 is more favourable than the whole reaction of glyoxal + NO2. The rate constants were calculated for the mentioned pathways using transition state theory for bimolecular steps and the fitted equations are reported.
乙二醛与NO2和NH2自由基的大气反应:吸氢机理和自然键轨道分析
乙二醛在大气化学中很重要,因为它有能力转化为二次有机气溶胶。本研究以6-311++G(d,p)基为基础,研究了NO2和NH2两种大气活性自由基在B3LYP和M06-2X水平下的乙二醛裂解反应。乙二醛与NO2/NH2自由基形成最稳定的加合物需要两个氢原子转移。分子内原子计算和自然键轨道分析证实了预测氢转移机理的准确性。计算结果表明,从动力学和热力学的角度来看,两种反应在M06-2X水平上的氢转移过程都是有利的。在自然键轨道分析中,B3LYP能级的稳定能E(2)离域改正量远高于M06-2X能级的结果(近两倍)。激活热力学参数表明,两个反应的第一步比第二步具有更低的势垒能。吉布斯自由能值估计在上述方法下两种反应的加合物都是自发的。乙二醛+ NH2的整个反应比乙二醛+ NO2的整个反应更有利。利用双分子步骤的过渡态理论计算了上述反应的速率常数,并给出了拟合方程。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
2.10
自引率
0.00%
发文量
5
审稿时长
2.3 months
期刊介绍: The journal covers the fields of kinetics and mechanisms of chemical processes in the gas phase and solution of both simple and complex systems.
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