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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Molecular Mechanism of HF Acid Ionization in Water: An Electronic Structure-Monte Carlo Study
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Molecular Mechanism of HF Acid Ionization in Water: An Electronic Structure-Monte Carlo Study

机译:水中氢氟酸电离的分子机理:电子结构-蒙特卡洛研究

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The results of a theoretical study of the acid ionization to form first a contact ion pair and then a solvent-separated ion pair are presented for HF in water. The ionization reaction to produce the contact ion pair is found to involve adiabatic quantum proton transfer (PT) and has an activation barrier in a collective solvent reaction coordinate of 2.9 kcal/mol, with a positive reaction free energy estimated as 2.2 kcal/mol. This result identifies the weakness of HF acid in aqueous solution as arising from this intrinsic acid ionization step, rather than from the thermodynamic difficulty of separating the ions so produced. The calculated charge distributions for the first step are in support of the unconventional Mulliken picture for PT. The second step to produce a solvent-separated ion pair is found to be sequential in connection with the first step, rather than concerted, and is also a quantum adiabatic PT. This reaction step proceeds via a solvent reaction coordinate and is slightly activated. The two step sequence in reverse order is discussed in connection with the Eigen picture of acid-base recombination aqueous solution.
机译:提出了酸离子化首先形成接触离子对,然后分离出溶剂分离的离子对的HF水溶液的理论研究结果。发现产生接触离子对的电离反应涉及绝热量子质子转移(PT),并且在2.9 kcal / mol的集体溶剂反应坐标中具有活化势垒,估计的正反应自由能为2.2 kcal / mol。该结果确定了水溶液中HF酸的弱点,这是由于该固有酸离子化步骤而不是由于分离如此产生的离子的热力学困难而引起的。第一步计算的电荷分布支持PT的非常规Mulliken图。发现产生溶剂分离的离子对的第二步与第一步有关,而不是一致的,并且也是绝热的PT。该反应步骤通过溶剂反应坐标进行并且被轻微活化。结合酸碱重组水溶液的本征图讨论了相反顺序的两步顺序。

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