具有混合的亲水-疏水特性的溶质的疏水水合仍然知之甚少。这是因为,无论是实验方法还是理论方法,都很难看到非极性溶质基团周围的冰状水结构,这与带有亲水基团的氢键不同。为了解决这个问题,我们通过红外光谱和理论方法(即DFT,ONIOM计算和AIMD模拟)研究了DMSO的水合作用,从而重新定义了其水合作用。在稀释的DMSO溶液中,在水分子与甲基氢(蓝移氢键)的相互作用下,在DMSO分子周围形成了包合物状水。笼子是由水分子构成的,这些水分子形成的能量和长度与SO基团和水分子之间具有可比的氢键。笼子的构造完成后,DMSO分子会在内部部分恢复其旋转自由度。框架内的强氢键被SO基团附近相对较小的水分子氢键弱化所掩盖,这是由于与DMSO氧原子键合的水分子氢的配位不当所致。我们还提出了对DMSO水溶液在共晶点高度高度不理想的混合行为的新解释,因为该体系中等摩尔量的分子配合物具有正过量熵。DMSO分子内部部分恢复了旋转自由度。框架内的强氢键被SO基团附近相对较小的水分子氢键弱化所掩盖,这是由于与DMSO氧原子键合的水分子氢的配位不当所致。我们还提出了对DMSO水溶液在共晶点高度非理想混合行为的新解释,因为该体系中分子复合物的等摩尔量的正过量熵。DMSO分子内部部分恢复了旋转自由度。框架内的强氢键被SO基团附近相对较小的水分子氢键弱化所掩盖,这是由于与DMSO氧原子键合的水分子氢的配位不当所致。我们还提出了对DMSO水溶液在共晶点高度非理想混合行为的新解释,因为该体系中分子复合物的等摩尔量的正过量熵。由于与大量水分子的不合适配合,氢分子与DMSO的氧原子键合。我们还提出了对DMSO水溶液在共晶点高度非理想混合行为的新解释,因为该体系中分子复合物的等摩尔量的正过量熵。由于与大量水分子的不合适配合,氢分子与DMSO的氧原子键合。我们还提出了对DMSO水溶液在共晶点高度非理想混合行为的新解释,因为该体系中分子复合物的等摩尔量的正过量熵。
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DMSO hydration redefined: Unraveling the hydrophobic hydration of solutes with a mixed hydrophilic–hydrophobic characteristic
Hydrophobic hydration of solutes with a mixed hydrophilic–hydrophobic characteristics is still poorly understood. This is because both experimental and theoretical methods find it difficult to see the ice-like water structure around the nonpolar solute groups, unlike hydrogen bonds with the hydrophilic groups. In order to unravel this problem, we have investigated DMSO hydration by means of infrared spectroscopy and theoretical methods, namely DFT, ONIOM calculations and AIMD simulations, which allowed us to redefine its hydration. In dilute DMSO solutions the clathrate-like water is formed around the DMSO molecule, supported by interactions of water molecules with the methyl hydrogens (the blue-shifted hydrogen bonds). The cage is constructed by water molecules that form hydrogen bonds of the comparable energy and length with the SO group and between water molecules. When the construction of the cage is completed, DMSO molecule partially regains its rotational freedom inside. Strong hydrogen bonds within the frame are masked by the relatively small population of weakened hydrogen bonds of water molecules in the vicinity of the SO group, due to the improper fit to the bulk water of water molecules hydrogen bonded to the oxygen atom of DMSO. We also propose a new explanation of the highly non-ideal mixing behavior of aqueous DMSO solutions at the eutectic point, as the positive excess entropy of the equimolar amounts of molecular complexes distinguished in the system.