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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >A Multi-State Empirical Valence Bond Model for Weak Acid Dissociation in Aqueuos Solution
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A Multi-State Empirical Valence Bond Model for Weak Acid Dissociation in Aqueuos Solution

机译：弱酸在水溶液中解离的多状态经验价键模型

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摘要

The development and application of a multistateempiricat valence bond (MS-EVE) model for a weak acid dissociation and subsequent proton transport in aqueous solution is described. The weak acid dissociation step is model~d by the inclusion of an additional EVE state describing the case when proton is bound to the acid's conjugate base. The model was parametrized tor the imidazolium cation deprotonation. Classical molecular dynamics simulation methodology was used to study both equilibrium and dynamic properties of this system. Free energy profiles of th~ deprotonation reaction, studied using a novel center of excess charge reaction coordinate, reveal the need to include several solvation shells around the weak acid in order to stabilize thehydronium species formed upon the weak acid deprotonation. The solvent atomic density plots examined at selected points along the proton transfer coordinate display a relatively large reorganization of the solvent around the weak acid molecule, caused by the shift in the weak acid molecule atomic point charges caused by the deprotonation. Finally, since the concentration of the weak acid in the system under study is low, its presence has only mimimal effect on the solvent diffusion and on the transfer dynamics of the excess proton in the water solution after the weak acid dissociation step.
机译：描述了用于弱酸解离和随后质子在水溶液中迁移的多态温度价键（MS-EVE）模型的开发和应用。弱酸解离步骤的模型是通过包含一个附加的EVE状态来描述的，该状态描述了质子与酸的共轭碱结合时的情况。参数化了咪唑鎓阳离子去质子化的模型。经典的分子动力学模拟方法用于研究该系统的平衡和动力学性质。使用新的过剩电荷反应坐标中心研究的去质子化反应的自由能谱表明，需要在弱酸周围包括多个溶剂化壳，以稳定在弱酸去质子化时形成的hydro。在质子传递坐标的选定点上检查的溶剂原子密度图显示，弱酸分子周围溶剂的重组相对较大，这是由去质子化导致的弱酸分子原子点电荷的移动引起的。最后，由于所研究体系中的弱酸浓度较低，因此弱酸解离步骤后，其存在对溶剂扩散和过量质子在水溶液中的转移动力学的影响极小。

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