Ground-State Intermolecular Proton Transfer of N2O4 and H2O: An Important Source of Atmospheric Hydroxyl Radical?
Ground-State Intermolecular Proton Transfer of N2O4 and H2O: An Important Source of Atmospheric Hydroxyl Radical?
复制标题
N2O4 和 H2O 的基态分子间质子转移：大气羟基自由基的重要来源？
DOI：
10.1021/jz300336s
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发表时间：
2012-05-03
影响因子：
5.7
通讯作者：
Chen, Xuebo
中科院分区：
文献类型：
--
作者：
Luo, Gefei;Chen, Xuebo
为了评价N2O4与H2O反应产生大气羟基自由基的意义，采用CASPT2//CASSCF和CASPT2//CASSCF/Amber QM/MM方法绘制了顺序反应、NO2二聚化和反式onono2分子间质子转移以及HONO光解的最小能量谱。发现在大气条件下，反式onono2分子间质子的高效基态转移主导了羟基自由基的生成。虽然质子转移效率很高，但二聚化前体反应产生反式onono2必须克服17.1 kcal/mol的势垒，无法与孤立的NO2单体对称生成O2N-NO2的无势垒通道竞争。我们的计算表明，没有屏障的HONO光解对大气羟基自由基的浓度确实有显著的贡献，但其重要性受到大气环境中缺乏反式onono2异构体的影响。
To evaluate the significance of the generation of atmospheric hydroxyl radical from reaction of N2O4 with H2O, CASPT2//CASSCF as well as CASPT2//CASSCF/Amber QM/MM approaches were employed to map the minimum-energy profiles of sequential reactions, NO2 dimerization and ground-state intermolecular proton transfer of trans-ONONO2 as well as the photolysis of HONO. A highly efficient ground-state intermolecular proton transfer of trans-ONONO2 is found to dominate the generation of hydroxyl radical under atmospheric conditions. Although proton transfer occurs with high efficiency, the precursor reaction of dimerization producing trans-ONONO2 has to overcome a 17.1 kcal/mol barrier and cannot compete with the barrierless channel of symmetric O2N-NO2 formation from isolated NO2 monomers. Our computations reveal that the photolysis of HONO without a barrier definitely makes significant contributions to the concentration of the atmospheric hydroxyl radical, but its importance is influenced by the lack of trans-ONONO2 isomer in the atmospheric environment.