【作者】 朱霄；

【导师】 李浩然；

【作者基本信息】 浙江大学 ， 化学， 2009， 博士

【摘要】 水溶液是自然界及化学化工生产中最普遍存在的一类体系,在各类生物、化学反应过程中扮演着重要的角色。水溶液体系内部广泛存在着分子间的缔合现象,这种源于分子间微观相互作用的特殊现象不但会使水溶液的微观结构发生改变,而且会导致其宏观性质如粘度、密度、汽液平衡等发生特定的变化,从而影响到水溶液在许多领域的应用。因此,对水溶液结构、性质的研究具有重要的理论意义和实际的应用价值。谱学方法具有准确、便捷的优点,因此被普遍用于定性、定量研究体系的结构和性质。本论文运用谱学方法结合理论模型对不同水溶液的内部结构及宏观性质进行了探索,并最终在谱学性质与溶液汽液平衡性质以及不同谱学性质之间建立了联系。本论文首先采用核磁共振化学位移结合局部组成模型研究了离子液体水溶液的局部结构。我们选用了1-乙基-3-甲基咪唑四氟硼酸(EmimBF4)和硝酸正丁胺(N4NO3)离子液体作为咪唑型和胺型离子液体的代表,在全浓度范围内测定了两种水溶液随浓度变化的质子化学位移,运用局部组成模型对离子液体和水的1HNMR化学位移分别进行关联,得到表征溶液内部微观环境的局部摩尔分数,进而对离子液体水溶液的结构进行分析。研究表明,分子间的缔合状态会随着溶液组成的变化而变化,在离子液体较多的区域内,离子液体更倾向于自身缔合而不是与水分子相互作用；水分子主要是与离子液体发生缔合,而水分子的自身缔合则相对较弱。为了进一步研究离子液体与水的相互作用,我们选用EmimBF4、氮甲基咪唑醋酸离子液体(MimCH3COO)和N4NO3离子液体作为咪唑型和胺型离子液体的代表,测定了富水区内离子液体、硝酸钾(KNO3)和氮甲基咪唑(N-methylimidazole)水溶液中,随浓度变化的水的1H NMR化学位移,通过分析δ(H20)的变化趋势,比较三种不同类型的溶质对水结构的影响。结果发现,不同类型的离子液体对水自身的网络结构产生不同的影响：EmimBF4、N4NO3离子液体的加入,使δ(H20)逐渐减小,表明这两种离子液体破坏了水的结构,使水变得更加无序,属于chaotrope型离子液体,与KN03的影响类似；而MimCH3COO离子液体的加入,使δ(H20)逐渐增大,表明这种离子液体增强了水的结构,使水变得更加有序,属于kosmotrope型离子液体,与N-甲基咪唑的影响类似。汽液平衡是水溶液另一个重要的宏观性质,与谱学性质一样,是溶液内部分子间作用的外在表现,如何在两者之间建立桥梁是学术界一直关心的问题。本课题组以前开展过利用核磁共振波谱和拉曼光谱推算溶液汽液平衡性质的工作,1H NMR化学位移和Raman频率位移都能用于预测汽液平衡,基于此,本论文尝试在红外光谱与汽液平衡性质之间建立定量关系。本论文提出了一个用于描述二元溶液C-H红外光谱频率的局部组成模型,该模型可以很好地关联甲醇／水等六个含水体系全浓度范围内的C-H红外光谱频率,然后结合无限稀释活度系数实现对汽液平衡的预测。这既证实了该模型的广泛适用性,又为获取溶液的汽液平衡提供了新的思路。既然1HNMR、Raman光谱和IR光谱都能用来预测水溶液的汽液平衡,那么这三种不同的谱学性质之间是否存在着某种内在联系呢?从这个问题出发,本论文采用局部组成模型,在1H NMR化学位移、Raman光谱频率位移和IR光谱频率之间进行了相互推算。本论文研究了有机溶剂水溶液体系(包括DMF、丙酮、甲醇和乙醇四种水溶液)和硝酸正丁胺N4N03离子液体水溶液体系。结果表明,不仅红外光谱与拉曼光谱这两种相似的振动光谱之间能够很好地相互推算,而且核磁共振波谱与振动光谱这两种完全不同的谱学性质之间也可以实现相互推算。总之,三种功能各异的谱学性质之间存在着定量的关系,能够通过局部组成模型进行相互推算,并且取得了令人满意的预测效果。总的说来,本论文运用谱学实验与理论模型相结合的方法,多角度地探讨了水溶液的结构及性质,从微观角度解释了水溶液特殊性质的内在因素,发现了水溶液不同宏观性质之间的定量关系,为进一步研究其他的水溶液体系以及溶液的其他性质开辟了思路。更多还原

【Abstract】 Apparently, aqueous solutions can be widely found in nature and industrial processes and are playing important role in chemical and biochemical fields. The association behavior, which results from the intermolecular interaction, has been detected in many aqueous solution systems. Such special phenomenon not only induce the change in the microcosmic structure, but also result in changes of macroscopical properties of aqueous solutions such as density, viscosity, vapor-liquid equilibrium and so on, which finally affects the application of aqueous solutions in many fields. Actually spectroscopy is an accurate and convenient approach and can offer us abundant information about intermolecular interaction within solutions. Consequently in the present work, the spectroscopy coupled with theory and model was combined to investigate the microcosmic configuration as well as macroscopical properties of various aqueous solutions.We first focused on the local structure of aqueous solution of ionic liquids (ILs) using 1H NMR chemical shifts and the local composition (LC) model. Ionic liquids involving 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) as well as n-butylammonium nitrate (N4NO3) are chosen in this paper as representative of imidazolium-based and ammonium-based ILs. The concentration-dependent chemical shifts of H2O and ILs protons have been obtained by 1H NMR experiments respectively. Then the obtained local mole fraction can be used to analyze the local structure of systems. The results indicated that in IL-rich region the self-association of IL played the dominant role, while water preferred to interact with IL rather than self-association. Instead, in water-rich region the network of water molecules was established, since the self-association of water predominated. This conclusion was highly consistent with others obtained by other methods such as IR, MD simulation and so on.In order to explore the interaction between water and ILs more clearly, we measured the concentration-dependent 1H NMR chemical shifts of water in aqueous solution of ionic liquids, including N4NO3, EmimBF4 and N-methylimidazole acetate [Mim][CH3COO]. Then the effect of ILs on the water structure was analyzed and compared with that of organic compounds as well as inorganic salt. It was revealed that the influence of ionic liquids on the water structure showed two different behaviors:[Mim][CH3C00] leads to the increase ofδ(H2O); however the presence of N4NO3 or [Emim][BF4] makeδ(H2O) decrease gradually in water-rich region. Consequently it can be concluded that ionic liquids can be classified into kosmotropes (structure makers) or chaotropes (structure breaker) according to their effects on the water structure.Vapor-liquid-equilibrium (VLE) is one of the important macroscopical thermodynamic properties of aqueous solutions, which also results from intermolecular interactions. Hereby how to establish the relationship between spectroscopy and VLE data of aqueous solutions is an interesting and hot topic. Actually it has been demonstrated that both of the 1H NMR chemical shifts and Raman frequency shifts can be used to predict VLE data. Therefore, we attempt to make clear the relationship between IR and VLE data. Firstly, we proposed a local composition model which can correlate concentration-dependent C-H IR frequency. Then VLE data were predicted by using the parameter obtained from correlation coupled with one infinite dilute activity efficient.Since all of 1H NMR, Raman and IR spectroscopy can be employed to predict VLE data, we wonder whether there are relationships among these different spectroscopic properties. Based on this, we chose two sorts of solutions:N4NO3 ionic liquid/water system and organic compounds/water systems including DMF/water, acetone/water, methanol/water and ethanol/water. Then we performed the prediction among 1H NMR chemical shifts, Raman frequency shifts and IR frequency by using local composition model. The results demonstrated that Raman and IR spectroscopy, which are vibrational spectra, can be successfully predicted form each other. Moreover there are quantitative relationship between NMR and vibrational spectra.All in all, the theory, model and spectroscopy experiments are combined to investigate the structure and property of aqueous solutions. Such frame of studying on aqueous solutions has been established successfully in this paper. In addition, we found that there was quantitative relationship among different spectroscopic properties. We expect that these methods are applicable to investigate many other kinds of aqueous solutions.更多还原