Mandal Imon, Zakai Itai, Karimova Natalia V, Johnson Mark A, Gerber R Benny
The Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Department of Chemistry, University of California, Irvine, California 92697, United States.
ACS Cent Sci. 2025 Mar 4;11(4):520-527. doi: 10.1021/acscentsci.4c02228. eCollection 2025 Apr 23.
Reactions of Cl, Br, and I ions in seawater with incoming molecules from the gas phase are of major atmospheric importance, but their mechanisms are mostly unknown. In this study, using ab initio molecular dynamics (AIMD) simulations, the microscopic mechanism of the halogen exchange reaction in water, HOCl + I → HOI + Cl, is unraveled. The main findings are as follows: (1) The reaction proceeds through a halogen-bonded isomer of the complex of HOCl with I, which is present in water and has a significant lifetime. The hydrogen-bonded isomer of the complex seems to play no role in the reaction. (2) Several water molecules act to catalyze the reaction through a Grotthuss-like mechanism that is totally different from that of halogen exchange in the gas phase. These results may have important implications for the chemistry of seawater, in particular for other reactions involving halogenated species.
海水中的氯离子、溴离子和碘离子与气相中进入的分子发生的反应具有重要的大气意义，但其反应机制大多未知。在本研究中，利用从头算分子动力学（AIMD）模拟，揭示了水中卤素交换反应HOCl + I → HOI + Cl的微观机制。主要发现如下：（1）反应通过HOCl与I形成的卤键异构体络合物进行，该络合物存在于水中且具有较长寿命。络合物的氢键异构体似乎在反应中不起作用。（2）几个水分子通过类似Grotthuss机制催化反应，这与气相中的卤素交换机制完全不同。这些结果可能对海水化学，特别是对涉及卤化物种的其他反应具有重要意义。
