用激光拉曼光谱研究乙醇对水分子氢键的影响

Effect of ethanol molecules on change of water hydrogen bonding with laser Raman spectra

为研究少量乙醇分子对纯水中氢键作用的影响，测量了0~10%体积浓度区间乙醇-水溶液和纯水中羟基伸缩振动的激光拉曼光谱，并根据不同样品拉曼光谱间的差分光谱分析了低浓度溶液中乙醇分子的水合作用。研究结果表明：当向纯水中加入少量乙醇分子至4%体积浓度的过程中，水分子的四面体氢键网状结构得到扩大，同时乙醇分子疏水基团周围的水分子间氢键作用也得到加强；随着溶液中乙醇浓度的增加，乙醇分子间由于疏水水合作用逐渐聚集到了一起，造成溶液中疏水基团与水分子总的作用面积减少，溶液中的水分子氢键网状结构变得松散，最终一些水分子会脱离氢键网状结构并以大小不等的团簇存在于溶液中，而乙醇分子的亲水基团则与其周围的自由水分子通过氢键缔合在一起。

In order to study the molecular interactions involved in dilute ethanol-water solutions, the OH stretching vibration spectra of ethanol-water solutions with the concentration range of 0-10 vol.% were measured, and the difference spectra of the samples were calculated. The hydration of ethanol molecule in the solutions of low concentration was analyzed based on the difference spectra. The result shows a very small amount of ethanol in the solution can enlarge the hydrogen bonding network in pure water, and the hydrogen bonding degree of water molecules around hydrophobic groups of ethanol molecules was also enforced. Ethanol molecules tend to aggregate together with increasing concentration, which was caused by hydrophobic hydration, and the hydrogen bonding network of water molecules become loosen due to this. As a result, some of the water molecules break away from the hydrogen bonding network, and transfer to small clusters of different size; at the same time, the hydrophilic groups of ethanol molecules associate with free water molecules through hydrogen bond.