<br>促进 HOCl + HOCl 反应在水/冷冻空气-水界面上生成 Cl2O,Journal of the American Chemical Society

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促进 HOCl + HOCl 反应在水/冷冻空气-水界面上生成 Cl2O
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-11-08 , DOI: 10.1021/jacs.4c11337
Weina Zhang, Dayuan Zheng, Haolin Han, Zhengyi Wan, Jie Zhong, Yuemeng Ji, Guiying Li, Joseph S. Francisco, Taicheng An

次氯酸（HOCl）被认为是一氧化二氯（Cl₂O）的临时储存库。以前的研究表明，Cl₂O 很难从 HOCl + HOCl 在气相中的反应生成。在这里，我们证明了 Cl₂O 可以由水/冷冻空气-水界面的 HOCl + HOCl 反应产生，这通过从头开始的分子动力学计算得到证实。与气相中的一步反应不同，我们的结果表明，在水/冷冻界面上从 HOCl + HOCl 生成 Cl₂O 涉及两个基本步骤，即一个 HOCl 去质子化和一个从另一个 HOCl 中提取 Cl。具体来说，已经研究了界面水/硝酸的中性/酸性催化以及氨、甲胺和二甲胺的碱催化机制。对于前者，HOCl 去质子化是限速步骤，Cl₂O 生成的总 k 在水界面增加到 9.23 × ^10-9-9.10 × ^10-1 ^M-1 ^s-1，在冻结界面增加到 3.20 × 10-7-4.10 × ^10-3 ^M-1 ^s-1，这至少比气态 k（3.31 × ^10-32 ^M-1 ^s-1）大 23 和 25 个数量级).对于后者，限速步骤更改为 Cl 抽象，其总 k 在水界面处急剧增加到 1.40–8.97 × 10⁷ M^–1 s^–1 和在冻结界面处 7.12–9.99 × 10⁶ M^–1 s^–1。有趣的是，Cl₂O 的生成速率顺序为二甲胺 < 甲胺 < 氨，并随着催化碱度的增加而降低。这些发现为了解 ClONO₂ + HOCl 反应以外的其他 Cl₂O 来源提供了新的见解。

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Promoting Cl2O Generation from the HOCl + HOCl Reaction on Aqueous/Frozen Air–Water Interfaces

Hypochlorous acid (HOCl) is considered a temporary reservoir of dichlorine monoxide (Cl₂O). Previous studies have suggested that Cl₂O is difficult to generate from the reaction of HOCl + HOCl in the gas phase. Here, we demonstrate that Cl₂O can be generated from the HOCl + HOCl reaction at aqueous/frozen air–water interfaces, which is confirmed by ab initio molecular dynamic calculations. Distinct from the one-step reaction in the gas phase, our results show that Cl₂O generation from HOCl + HOCl on aqueous/frozen interfaces involves two elementary steps, namely, one HOCl deprotonation and one Cl-abstraction from the other HOCl. Specifically, the mechanisms of neutral/acidic catalysis from interfacial water/nitric acid and base catalysis from ammonia, methylamine and dimethylamine have been examined. For the former, HOCl deprotonation is the rate-limiting step, and the total k of Cl₂O generation increases to 9.23 × 10^–9–9.10 × 10^–1 M^–1 s^–1 at the aqueous interface and 3.20 × 10^–7–4.10 × 10^–3 M^–1 s^–1 at the frozen interface, which is at least 23 and 25 orders of magnitude greater than that of gaseous k (3.31 × 10^–32 M^–1 s^–1). For the latter, the rate-limiting step is changed to Cl-abstraction, whose total k dramatically increases to 1.40–8.97 × 10⁷ M^–1 s^–1 at the aqueous interface and 7.12–9.99 × 10⁶ M^–1 s^–1 at the frozen interface. Interestingly, the Cl₂O production rates ranked in the order of dimethylamine < methylamine < ammonia and decreased with increasing catalytic alkalinity. These findings provide new insights for understanding other Cl₂O sources beyond the ClONO₂ + HOCl reaction.

更新日期：2024-11-08

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