Mechanisms of Noncatalytic Organic Chemical Reactions in Super- and Subcritical Water

引入了稀溶液中分子构型的能量表示，用来表示溶质周围的溶剂在一维坐标上的分布，该坐标指定了溶质-溶剂相互作用能。在这种表示中，溶质-溶剂相互作用势的集合与分布函数的集合是一一对应的。在一一对应的基础上，在溶质-溶剂相互作用的排斥区采用类Percus-Yevick近似和在吸引区采用类超网链近似，构造了溶质在溶液中的化学势的近似泛函。然后，化学势被精确地赋予与溶剂密度和溶质-溶剂相互作用有关的第二级。结果表明，在广泛的热力学条件下，从单一泛函出发可以准确、有效地计算非极性、极性和离子型溶质在水中的化学势。此外，蛋白质等纳米级分子的构象因溶质-溶剂相互作用的影响而变化很大。因此，需要建立一种方法来计算具有构象柔性的溶质分子的溶剂化自由能，以处理具有重要功能的溶液体系。将能量表示法推广到处理柔性溶质分子的溶剂化自由能，在这项工作中，我们考察了具有伸缩和/或扭转自由度的水中分子内运动的溶质体系，并证明了该方法在包括常温和超临界在内的广泛热力学条件下的性能。疏水和亲水溶质在水中的聚集行为也在相同的框架内处理。

The energy representation of the molecular configuration in a dilute solution is introduced to express the solvent distribution around the solute over a one-dimensional coordinate specifying the solute-solvent interaction energy. In this representation, the correspondence is shown to be one-to-one between the set of solute-solvent interaction potentials and the set of distribution functions On the basis of the one-to-one correspondence, an approximate functional for the chemical potential of a solute in solution is constructed by adopting the Percus-Yevick-like approximation in the repulsive region of the solute-solvent interaction and the hypernetted-chain-like approximation in the attractive region. The chemical potential is then given exactly to second order with respect to the solvent density and to the solute-solvent interaction. It is demonstrated that the chemical potentials of nonpolar, polar, and ionic solutes in water are evaluated accurately and efficiently from the single functional over a wide range of thermodynamic conditions. Furthermore, the conformation of a nanoscale molecule such as protein varies strongly in response to solute-solvent interactions. An approach to the solvation free energy of a solute molecule with conformational flexibility thus needs to be established toward treating a solution system of functional importance. The method of energy representaion is extended to treat the solvation free energy of a flexible solute molecule, In this work, we examined solute systems in water with stretching and/or torsioal degrees of freedom for intramolecular motion, and demonstrated the performance of the method over a wide range of thermodynamic conditions including both ambient and supercritical. The aggregation behaviors of hydrophobic and hydrophilic solutes in water are also treated within the same framework.