Acid dissociation under hydrostatic pressure: Structural implications for volumetric parameters.
Acid dissociation under hydrostatic pressure: Structural implications for volumetric parameters.
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静水压力下的酸解离：体积参数的结构影响。
DOI：
10.1016/j.molliq.2021.115512
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
T.*
中科院分区：
文献类型：
--
作者：
Miyagawa;A.*; Fukuhara;G.; Okada;T.*
在这里，我们通过光谱方法，包括化学计量学辅助的直接和间接吸收光谱，评估了pH指示剂染料和氨基酸的酸解离常数(PKA)的压力依赖性。这些数据可用于考虑极端条件下的分子性质，例如在深海中。我们证实了摩尔体积差(ΔV°)和摩尔可压缩性差(Δκ)之间的正相关性，用于这里和文献中所考察的分子的去质子化。基于去质子化时分子结构的变化和相关的水合变化，讨论了这种关系。羧基或酚羟基的去质子化导致负的ΔV°，而当分子因去质子化而失去正电荷时，则具有正的ΔV°。这可以解释为去质子化导致分子周围水合球体大小的变化。去质子化使水合球体收缩，导致ΔV°和Δκ为负，尤其是羧酸和酚类。相反，当去质子化导致水化球体膨胀时，ΔV°和Δκ都是正数。因此，基于去质子化过程中水化结构的变化，解释了ΔV°与Δκ数据之间的正相关性。
Here, we evaluate the pressure dependencies of the acid dissociation constants (pKa) of pH indicator dyes and amino acids by spectroscopic methods, including chemometric-assisted direct and indirect absorption spectrometry. These data can be useful for considering molecular properties under extreme conditions, such as in deep sea. We confirmed a positive correlation between the molar volume difference (ΔV°) and the molar compressibility difference (Δκ) data for the deprotonation of molecules examined here and in literature. This relationship is discussed based on structural changes in the molecules upon deprotonation and associated hydration changes. Deprotonation from a carboxyl or phenolic hydroxyl group results in a negative ΔV°, whereas a molecule has positive ΔV° when it loses a positive charge by deprotonation. This can be interpreted as a deprotonation-induced change in the size of the hydration sphere around the molecule. The contraction of the hydration sphere by deprotonation leads to negative ΔV° and Δκ, particularly for carboxylic acids and phenols. In contrast, when deprotonation causes the hydration sphere to expand, both ΔV° and Δκare positive. Thus, a positive correlation between ΔV° and Δκdata is interpreted based on the hydration structural change upon deprotonation.