Ab Initio Molecular Dynamics Simulations of the Influence of Lithium Bromide Salt on the Deprotonation of Formic Acid in Aqueous Solution

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Daub , C D & Halonen , L 2019 , ' Ab Initio Molecular Dynamics Simulations of the Influence of Lithium Bromide Salt on the Deprotonation of Formic Acid in Aqueous Solution ' , Journal of Physical Chemistry B , vol. 123 , no. 31 , pp. 6823-6829 . https://doi.org/10.1021/acs.jpcb.9b04618

Title: Ab Initio Molecular Dynamics Simulations of the Influence of Lithium Bromide Salt on the Deprotonation of Formic Acid in Aqueous Solution
Author: Daub, Christopher D.; Halonen, Lauri
Contributor: University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
Date: 2019-08-08
Language: eng
Number of pages: 7
Belongs to series: Journal of Physical Chemistry B
ISSN: 1520-6106
URI: http://hdl.handle.net/10138/305210
Abstract: The deprotonation of formic acid is investigated using metadynamics in tandem with Born-Oppenheimer molecular dynamics simulations. We compare our findings for formic acid in pure water with previous studies before examining formic acid in aqueous solutions of lithium bromide. We carefully consider different definitions for the collective variable(s) used to drive the metadynamics, emphasizing that the variables used must include all of the possible reactive atoms in the system, in this case carboxylate oxygens and water hydrogens. This ensures that all the various possible proton exchange events can be accommodated and the collective variable(s) can distinguish the protonated and deprotonated states, even over rather long ab initio simulation runs (ca. 200-300 ps). Our findings show that the formic acid deprotonation barrier and the free energy of the deprotonated state are higher in concentrated lithium bromide, in agreement with the available experimental data for acids in salt solution. We show that the presence of Br- in proximity to the formic acid hydroxyl group effectively inhibits deprotonation. Our study extends previous work on acid deprotonation in pure water and at air-water interfaces to more complex multicomponent systems of importance in atmospheric and marine chemistry.
Subject: STOICHIOMETRIC DISSOCIATION-CONSTANTS
CARBONIC-ACID
MECHANISTIC INSIGHTS
LIQUID WATER
ACETIC-ACID
METADYNAMICS
SEAWATER
DECOMPOSITION
POTASSIUM
H2CO3
116 Chemical sciences
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