Bowron Daniel T, Finney John L, Soper Alan K
ISIS Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK.
J Phys Chem B. 2006 Oct 19;110(41):20235-45. doi: 10.1021/jp064170v.
Hydrogen/deuterium isotopic substitution neutron diffraction techniques were used to measure the structural correlation functions in a 0.23 mole fraction solution of tetrahydrofuran in water at room temperature. Empirical potential structure refinement (EPSR) was used to build a three-dimensional model of the liquid structure that is consistent with the experimental data. Detailed analysis shows a preference for nonpolar interactions between the cyclic ether molecules plus polar interactions between the ether and solvent water and hydrophobic hydration of the nonpolar regions of the solute. The increase in the number of hydrogen-bond-acceptor sites relative to the number of hydrogen-bond-donor sites in this system, compared to the balanced situation that would be found in pure water, has a marked compressive effect on the structure of the solvent. Despite the small size of the solvent water molecules, the 0.23 mole fraction aqueous solution is still found to contain small voids akin to those in pure liquid tetrahydrofuran. In contrast to the positive surface charge of the voids in the pure system, the average void in this aqueous solution is found to have a net negative charge. This is due to contributions from the water oxygen atoms that are negatively polarized by their intramolecular bonding.
采用氢/氘同位素取代中子衍射技术，在室温下测量了四氢呋喃在水中摩尔分数为0.23的溶液中的结构关联函数。利用经验势能结构精修（EPSR）构建了与实验数据一致的液体结构三维模型。详细分析表明，环状醚分子之间存在非极性相互作用，醚与溶剂水之间存在极性相互作用，溶质的非极性区域存在疏水水合作用。与纯水中的平衡情况相比，该体系中氢键受体位点数量相对于氢键供体位点数量的增加，对溶剂结构具有显著的压缩作用。尽管溶剂水分子尺寸较小，但仍发现摩尔分数为0.23的水溶液中含有类似于纯液态四氢呋喃中的小空隙。与纯体系中空隙的正表面电荷相反，该水溶液中的平均空隙具有净负电荷。这是由于水分子中的氧原子通过分子内键合而产生负极化的贡献。
