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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Interpretation of Br0nsted Acidity by Triadic Paradigm:A G3 Study of Mineral Acids
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Interpretation of Br0nsted Acidity by Triadic Paradigm:A G3 Study of Mineral Acids

机译：用三重范式解释布朗斯台德酸度：矿物酸的G3研究

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Deprotonation enthalpies and the gas-phase acidities of 24 inorganic acids are calculated by using composite G3 and G2 methodologies.The computed values are in very good accordance with available measured data.It is found that the experimental DELTA H_(acid)values of the FSO3H and CF3SO3H are too high by some 6 and 7 kcal mol~(-1),respectively.Furthermore,a new DELTA H_(acid)value for HClO4 of 300 kcal mol~(-1)is recommended and suggested as a threshold of superacidicity in the gas phase.The calculated deprotonation enthalpies are interpreted by employing the trichotomy paradigm.Taking into account that the deprotonation enthalpy is a measure of acidity,it can be safely stated that the pronounced acidities of mineral acids are to a very large extent determined by Koopmans'term with very few exceptions,one of them being H2S.To put it in another way,acidities are predominantly a consequence of the ability of the conjugate bases to accommodate the excess electron charge,since Koopmans'term in trichotomy analysis is related to conjugate base anion.The final state is decisive in particular for superacids like ClSO3H,CF3SO3H,HClO4,HBF4,HPF6,HAlCl4,and HAlBr4.However,in the latter two molecules the bond dissociation energy of the halogen-H bond substantially contributes to their high acidity too.Therefore,acidity of these two most powerful superacids studied here is determined by cooperative influence of both initial and final state effects.It should be emphasized that acidity of hydrogen halides HC1 and HBr is a result of concerted action of all three terms included in triadic analysis.A byproduct of the triadic analysis are the first adiabatic ionization energies of the anionic conjugate bases.They are in fair to good agreement with the experimental data,which are unfortunately sparse.A fairly good qualitative correlation is found between the gas-phase deprotonation enthalpies of six mineral O-H acids and available Hammett-Taft sigma_p~-constants of the corresponding substituent groups.
机译：采用复合G3和G2方法计算了24种无机酸的质子化焓和气相酸度，计算值与现有的实测数据非常吻合，发现FSO3H的实验DELTA H_（酸）值和CF3SO3H分别过高约6和7 kcal mol〜（-1）。此外，建议新的HClO4的DELTA H_（酸）值为300 kcal mol〜（-1），并作为超酸性的阈值考虑到去质子化焓是对酸度的量度，可以安全地说，无机酸的显着酸度在很大程度上取决于Koopmans术语几乎没有例外，其中一个是H2S。换句话说，酸度主要是由于共轭碱能够容纳过量电子电荷的结果，因为Koopmans三分法分析中的m与共轭碱阴离子有关。最终状态尤其对ClSO3H，CF3SO3H，HClO4，HBF4，HPF6，HAlCl4和HAlBr4等超酸起决定性作用。 -H键也大大有助于其高酸度。因此，本文研究的这两种最强的超酸的酸度取决于初始和最终状态效应的协同影响。应强调的是卤化氢HC1和HBr的酸度是结果三元组分析中所有三个术语的协同作用。三元组分析的副产物是阴离子共轭碱的第一个绝热电离能。它们与实验数据相当吻合，不幸的是稀疏。在六种矿物OH酸的气相去质子化焓与相应亚基的可用Hammett-Taft sigma_p〜-常数之间发现了定性相关性选民群体。

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