Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media

Imon Mandal; Itai Zakai; Natalia V. Karimova; Mark A. Johnson; R. Benny Gerber

doi:10.1021/acscentsci.4c02228

Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media

Imon Mandal, Itai Zakai, Natalia V. Karimova, Mark A. Johnson, R. Benny Gerber^*

^*Corresponding author for this work

Institute of Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

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.

Original language	English
Pages (from-to)	520-527
Number of pages	8
Journal	ACS Central Science
Volume	11
Issue number	4
DOIs	https://doi.org/10.1021/acscentsci.4c02228
State	Published - 23 Apr 2025

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© 2025 The Authors. Published by American Chemical Society.

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title = "Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media",

abstract = "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.",

author = "Imon Mandal and Itai Zakai and Karimova, \{Natalia V.\} and Johnson, \{Mark A.\} and Gerber, \{R. Benny\}",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors. Published by American Chemical Society.",

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doi = "10.1021/acscentsci.4c02228",

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AU - Mandal, Imon

AU - Zakai, Itai

AU - Karimova, Natalia V.

AU - Johnson, Mark A.

AU - Gerber, R. Benny

PY - 2025/4/23

Y1 - 2025/4/23

N2 - 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.

AB - 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.

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Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media

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