The atmospheric oxidation of dimethyl, diethyl, and diisopropyl ethers. The role of the intramolecular hydrogen shift in peroxy radicals
The atmospheric oxidation of dimethyl, diethyl, and diisopropyl ethers. The role of the intramolecular hydrogen shift in peroxy radicals
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二甲醚、二乙醚和二异丙醚的大气氧化。
DOI：
10.1039/c5cp07199b
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发表时间：
2016
影响因子：
3.3
通讯作者：
Wang LM
中科院分区：
文献类型：
--
作者：
Wang Sainan;Wang Liming;Wang Liming;Wang LM;Wang LM
采用量子化学和单分子反应理论（RRKM-ME）方法研究了二甲醚（DME）、二乙醚（DEE）和二异丙醚（DiPE）的大气氧化机理。对于来自DME的过氧自由基CH 3 OCH 2 O2，发现其分子内H-位移到stecCH 2 OCH 2 OOH的势垒高度为1.85 kJ mol−1，其可以与大气中的O2快速复合。RRKM-ME计算得到在298 K时形成stecO 2CH 2 OCH 2 OOH的有效速率为10.1 s−1。对于DEE和DiPE中的类似自由基，有效速率分别为1.6 s-1和1.1 s-1。在大气中，这些单分子反应足够快，足以与NO和/或HO 2的双分子反应竞争，特别是当[NO]低时。自由基的命运后的H-移位也在这里检查。几个后续的反应被发现回收OH自由基。在此基础上提出了新的机理，并与前人的实验结果相一致。在大气中，通过H-位移的途径代表了这些醚的自动氧化，没有NOx的参与，因此没有O3的形成，以及由于OH自由基的再循环而产生的有机化合物的自清洁机制。一些最终产物被高度氧化，具有多官能基团和高O：C比，这表明它们的低挥发性和对二次有机气溶胶的潜在贡献。
The atmospheric oxidation mechanisms of dimethyl ether (DME), diethyl ether (DEE) and diisopropyl ether (DiPE) are studied by using quantum chemistry and unimolecular reaction theory (RRKM-ME) calculations. For the peroxy radical CH3OCH2O2˙ from DME, a barrier height of ∼85 kJ mol−1 is found for its intramolecular H-shift to ˙CH2OCH2OOH, which can recombine rapidly with the atmospheric O2. RRKM-ME calculations obtain an effective rate of ∼0.1 s−1 at 298 K for the formation of ˙O2CH2OCH2OOH. For similar radicals in DEE and DiPE, effective rates are 1.6 s−1 and 1.1 s−1, respectively. In the atmosphere, these unimolecular reactions are fast enough to compete with the bimolecular reactions with NO and/or HO2, especially when [NO] is low. The fates of radicals after the H-shifts are also examined here. Several subsequent reactions are found to recycle OH radicals. New mechanisms are proposed on the basis of present calculations and are consistent with previous experimental results. In the atmosphere, the routes via H-shifts represent an auto-oxidation of these ethers with no involvement of NOx and therefore no O3 formation, and also a self-cleaning mechanism of organic compounds due to recycling of OH radicals. Some of the end products are highly oxidized with multifunctional groups and high O : C ratios, suggesting their low volatility and potential contribution to secondary organic aerosols.