Chao Wen, Jr-Min Lin Jim, Takahashi Kaito, Tomas Alexandre, Yu Lu, Kajii Yoshizumi, Batut Sébastien, Schoemaecker Coralie, Fittschen Christa
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
Sciences de l'Atmosphère et Génie de l'Environnement SAGE, IMT Lille Douai, 941 Rue Charles Bourseul, 59508, Douai, France.
Angew Chem Int Ed Engl. 2019 Apr 1;58(15):5013-5017. doi: 10.1002/anie.201900711. Epub 2019 Mar 6.
Recent reports [Jara-Toro et al., Angew. Chem. Int. Ed. 2017, 56, 2166 and PCCP 2018, 20, 27885] suggest that the rate coefficient of OH reactions with alcohols would increase by up to two times in going from dry to high humidity. This finding would have an impact on the budget of alcohols in the atmosphere and it may explain differences in measured and modeled methanol concentrations. The results were based on a relative technique carried out in a small Teflon bag, which might suffer from wall reactions. The effect was reinvestigated using a direct fluorescence probe of OH radicals, and no catalytic effect of H O could be found. Experiments in a Teflon bag were also carried out, but the results of Jara-Toro et al. were not reproducible. Further theoretical calculations show that the water-mediated reactions have negligible rates compared to the bare reaction and that even though water molecules can lower the barriers of reactions, they cannot make up for the entropy cost.
最近的报告[Jara-Toro等人，《德国应用化学》2017年，第56卷，2166页；《物理化学化学物理》2018年，第20卷，27885页]表明，从干燥到高湿度条件下，OH与醇类反应的速率系数会增加高达两倍。这一发现将对大气中醇类的收支产生影响，并且可能解释实测甲醇浓度与模型预测浓度之间的差异。这些结果基于在一个小型特氟龙袋中进行的相对技术，但该技术可能存在壁面反应。使用OH自由基的直接荧光探针重新研究了该效应，未发现H₂O的催化作用。也在特氟龙袋中进行了实验，但Jara-Toro等人的结果无法重现。进一步的理论计算表明，与直接反应相比，水介导的反应速率可忽略不计，并且尽管水分子可以降低反应势垒，但它们无法弥补熵损失。
