School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China.
School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou 510640, China; Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, South China University of Technology, Guangzhou 510006, China.
Chemosphere. 2014 Sep;111:537-44. doi: 10.1016/j.chemosphere.2014.04.067. Epub 2014 May 27.
The atmospheric oxidation mechanism of chlorobenzene (CB) initiated by the OH radicals is investigated at M06-2X/6-311++G(2df, 2p) and ROCBS-QB3 levels. The oxidation is initiated by OH addition to the ortho (∼50%), para (∼33%) and meta (∼17%) positions, forming CB-OH adducts as R2, R3, and R4; while the ipso-addition is negligible (∼0.2%). The reactions of the CB-OH adducts with the atmospheric oxygen are further investigated in detail by coupling the unimolecular reaction rate theory calculations with master-equation (RRKM-ME). The CB-OH adducts react with O2 either by irreversible H-abstraction to form chlorophenol and HO2 or by reversible additions to form CB-OH-O2 radicals, which subsequently cyclize to bicyclic radicals. RRKM-ME calculations show that the addition reactions of CB-OH and O2 at the atmospheric pressure are close to but not yet reach their high-pressure-limits. The RRKM-ME simulations predict the yields of 93%, 38%, and 74% for ortho-, meta- and para-chlorophenols from the reactions of O2 with R2, R3 and R4, being lower than their high-pressure-limit yields of 95%, 48%, an 80%, respectively. Overall, the yield of chlorophenols is determined as 72% at the atmospheric pressure.
采用 M06-2X/6-311++G(2df, 2p) 和 ROCBS-QB3 理论水平研究了 OH 自由基引发的氯苯（CB）的大气氧化机制。氧化反应由 OH 在邻位（50%）、对位（33%）和间位（17%）的加成引发，形成 CB-OH 加合物 R2、R3 和 R4；而 ipso-加成可忽略不计（0.2%）。通过将单分子反应速率理论计算与主方程（RRKM-ME）耦合，进一步详细研究了 CB-OH 加合物与大气氧的反应。CB-OH 加合物与 O2 反应要么通过不可逆的 H 抽提形成氯苯酚和 HO2，要么通过可逆加成形成 CB-OH-O2 自由基，随后环化形成双环自由基。RRKM-ME 计算表明，在大气压力下，CB-OH 和 O2 的加成反应接近但尚未达到其高压极限。RRKM-ME 模拟预测，O2 与 R2、R3 和 R4 反应生成邻氯苯酚、间氯苯酚和对氯苯酚的产率分别为 93%、38%和 74%，低于其高压极限产率分别为 95%、48%和 80%。总体而言，在大气压力下，氯苯酚的产率为 72%。
