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有机胺对二氧化氮水解反应的理论研究及两性离子的探讨
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摘要
大气中的亚硝酸(HONO)~([1],[2])是羟基自由基(OH)的一个重要的来源,并且对大气化学环境有重要的影响。同时,有机胺和水广泛的存在于大气环境中。本文对分子簇复合物2NO_2-mH_2O-CH_3NH_2(m=1-3)和2NO_2-mH_2O-(CH_3)_2NH(m=1,2)进行了理论模拟研究。计算结果表明:对于二氧化氮的水解反应,有机胺在热力学和动力学方面都要比无机氨具有更大的影响。反应中增加水分子不仅可以降低反应的能垒,也可以促进硝酸甲胺盐中离子对结构的形成。对于CH_3NH_2-COS-(H_2O)_n,CH_3NH_2-NO_2-(H_2O)_n和CH_3NH_2-SO_2-(H_2O)_n(n=0-8)复合物中是否存在两性离子结构的进一步研究,发现了CH_3NH_2~+COS~-的两性离子结构,然而,在复合物CH_3NH_2-NO_2-(H_2O)_n和CH_3NH_2-SO_2-(H_2O)_n中两性离子结构并没有明显的形成。
Atmospheric nitrous acid(HONO) is a significant source of hydroxyl(OH) radicals responsible for the initiation of photochemical smog, while amines and water are widely exists in the atmosphere.In this paper, we report a detailed theoretical study of two series of the molecular clusters 2NO_2-mH_2O-CH_3NH_2(m=1-3) and 2NO_2-mH_2O-(CH_3)_2NH(m=1, 2).Calculated results show that amines have larger effects than ammonia in promoting the hydrolysis reaction of NO_2 on thermodynamics and kinetics.The additional water molecules can not only reduce the reaction energy barrier, but also promote to form MAN(CH_3NH_3~+NO_3~-) with ion-pair structure.The zwitterion(CH_3NH_2~+COS~-) can be formed in the clusters of CH_3NH_2-COS-(H_2O)_n, however, the zwitterion in CH_3NH_2-NO_2-(H_2O)_n and CH_3NH_2-SO_2-(H_2O)_n(n=0-8) are not formed distinctly.
引文
[1]Elshorbany,Y.F.;Crutzen,P.J.;Steil,B.;Pozzer,A.;Tost,H.;Lelieveld,J.Atmospheric Chemistry and Physics.2014,14:1167.
    [2]Donaldson,M.A.;Berke,A.E.;Raff,J.D.Environmental science&technology.2014,48:375.

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