Shah Prateek P, Roberts Christopher J
Department of Chemical Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, USA.
J Phys Chem B. 2008 Jan 31;112(4):1049-52. doi: 10.1021/jp075783q. Epub 2008 Jan 9.
A novel approach is presented for interpreting and potentially predicting values of the isothermal, isobaric transfer free energy, entropy, and enthalpy (Deltamicrotr2, Deltastr2, and Deltahtr2) for a solute between water and water-cosolvent mixtures. The approach explicitly accounts for volumetric properties of the solvent and solute (the equation of state, EoS) and casts the overall transfer process as a thermodynamic cycle with two stages: (1) isothermal solvent exchange from pure water to the cosolvent composition of interest at fixed mass density; (2) isothermal expansion or compression at the final solvent composition to recover the pressure of the initial state. Using molecular simulations with methane as the solute, the analysis is illustrated over a wide range of cosolvent concentrations for sorbitol-, ethanol-, and methanol-water binary mixtures. The EoS contribution semiquantitatively or quantitatively captures Deltamicrotr2, Deltastr2, and Deltahtr2 in almost all cases tested, highlighting the importance of considering the effects of changes in solvent density on the overall transfer process. The results also indicate that apolar solvation at these length scales is dominated by the work of cavity formation across a range of cosolvent species and concentrations.
本文提出了一种新方法，用于解释并可能预测溶质在水和水 - 共溶剂混合物之间的等温、等压转移自由能、熵和焓（Δμtr2、Δstr2和Δhtr2）的值。该方法明确考虑了溶剂和溶质的体积性质（状态方程，EoS），并将整个转移过程描述为一个具有两个阶段的热力学循环：（1）在固定质量密度下，将溶剂从纯水等温交换为目标共溶剂组成；（2）在最终溶剂组成下进行等温膨胀或压缩，以恢复初始状态的压力。以甲烷为溶质进行分子模拟，对山梨醇、乙醇和甲醇 - 水二元混合物在广泛的共溶剂浓度范围内进行了分析。在几乎所有测试案例中，EoS贡献都能半定量或定量地捕捉到Δμtr2、Δstr2和Δhtr2，突出了考虑溶剂密度变化对整个转移过程影响的重要性。结果还表明，在这些长度尺度上，非极性溶剂化主要由一系列共溶剂种类和浓度下的空穴形成功主导。
