【作者】 杨博；

【导师】 孙成林；

【作者基本信息】 吉林大学 ， 光学， 2020， 硕士

【摘要】 本文利用自发拉曼光谱技术分别对二甲基亚砜（DMSO）、乙酸和甲醇三种典型有机分子水溶液的分子间相互作用规律及对应的氢键结构进行了研究。通过测量溶液的拉曼光谱,分析有机分子特征峰的频移变化,可以直接获得分子振动和转动信息,有助于了解不同浓度的有机分子水溶液中共价键的振动频率,从而精确地分析水溶液中氢键和团簇结构随外界条件变化的微观物理过程。首先,测量并研究了不同体积分数占比下DMSO水溶液的自发拉曼光谱。我们发现当DMSO体积分数占比小于0.6时,对称和反对称OH伸缩振动模式对应的拉曼峰快速向更低的频率方向移动;当DMSO体积分数占比大于0.6时,这两个拉曼峰频移方向则完全相反。这些结果说明DMSO与水分子之间的强氢键在浓度较低时有助于加强水分子的四面体结构,而在浓度较高时,DMSO分子的加入则对水的四面体结构起到破坏作用。更重要的是,当DMSO体积分数占比大于0.6时,S=O基团对应拉曼峰的蓝移幅度明显增大,这表明DMSO与水分子形成的团簇结构可能发生了巨大变化。此外,通过对不同振动模式的C-H基团对应的拉曼峰进行研究,发现DMSO的非极性甲基与水分子发生了疏水水合作用。其次,测量并研究了不同体积分数占比下乙酸水溶液的自发拉曼光谱。结果表明,当乙酸的体积分数占比分别达到0.3和0.8时,光谱先后出现两次拐点,对应乙酸-水团簇发生了两次结构变化。更重要的是,C-H基团对应的拉曼峰在乙酸体积分数占比达到0.8时发生了显著蓝移,这是由于乙酸-乙酸团簇结构变化引起的,标志着乙酸侧二聚体的形成。此外,通过理论分析得到了乙酸水溶液中团簇结构（水合单体,线性二聚体,乙酸侧二聚体和水分离二聚体）的详细变化过程。最后,测量并研究了不同体积分数占比下甲醇水溶液的自发拉曼光谱。结果表明当甲醇的体积分数占比达到0.4时,甲醇与水分子之间的氢键发生了显著变化,导致对应的团簇结构亦随之改变。此外,当甲醇的体积分数占比超过0.4时,我们发现甲醇的C-O伸缩振动模式存在明显的蓝移,而对称和反对称的C-H伸缩振动模式却出现显著红移。这些实验结果说明甲醇的CH₃基团并未与水分子形成氢键,并且C-H的红移是受到了C-O键形成氢键的影响。本文的研究结果有助于理解DMSO、乙酸和甲醇三种典型有机分子水溶液的物理化学性质,并进一步推进生命科学和化工合成等领域关于有机分子水溶液的氢键及溶剂化效应的相关研究。更多还原

【Abstract】 In this paper,intermolecular interactions and corresponding hydrogen bonding structures in aqueous solutions of dimethyl sulfoxide（DMSO）,acetic acid,and methanol have been studied using spontaneous Raman spectroscopy,respectively.The information of molecular vibration and rotation can be obtained directly by measuring the Raman spectrum of the solution and analyzing the frequency shift of the characteristic peaks of organic molecules,which is helpful to understand the vibration frequency of covalent bond in the aqueous solution of organic molecules with different concentrations,so as to accurately analyze the microphysical process of hydrogen bond and cluster structure in the aqueous solution changing with the external conditions.Firstly,the Raman spectra of DMSO-water binary solutions with different mixing ratio were measured and studied.We found that the Raman peaks of the symmetrical and asymmetric OH stretching vibration modes of water move quickly to lower frequencies when the volume fraction of DMSO is less than 0.6,and the frequency shifts of the symmetric and asymmetric OH stretching modes are completely opposite when the volume fraction of DMSO exceeds 0.6.These results show that the strong hydrogen bond between DMSO and water molecules is helpful to strengthen the tetrahedral structure of water at a lower concentration,while the addition of DMSO molecules has a destructive effect on the structure of water at a higher concentration.Moreover,the blue shift of the Raman peak of S=O group increases obviously when the volume fraction of DMSO exceeds 0.6,which indicates that the cluster structure between DMSO and water molecules may have changed greatly.In addition,the Raman peaks of C-H groups with different vibration modes were studied.It was found that the non-polar methyl group of DMSO had hydrophobic hydration with water molecules.Secondly,the Raman spectra of acetic acid-water binary solutions with different mixing ratio were measured and investigated.The results show that there are two inflexion points in the spectrum when the volume fraction of acetic acid reaches 0.3and 0.8 respectively,corresponding to two structural changes of acetic acid-water clusters.Moreover,the Raman peak of C-H group undergoes a significant blue shift when the volume fraction of acetic acid reaches 0.8,which is caused by the structural change of the acetic acid-acetic acid cluster,indicating the formation of acetic acid side-on dimers.At last,the detailed changes of the cluster structure（hydrated monomer,linear dimer,acetic acid side-on dimer and water-separated dimer）in the acetic acid aqueous solution were obtained through theoretical analysis.Finally,the Raman spectra of methanol-water binary solution with different mixing ratio are measured and discussed.The results show that the hydrogen bonding between methanol and water changes significantly when the volume fraction of methanol reaches 0.4,resulting in the corresponding cluster structure changes.In addition,we found that the C-O stretching vibration mode of methanol shows a significant blue shift when the volume fraction of methanol exceeds 0.4,while the symmetrical and asymmetric stretching vibration modes of C-H show a significant red shift.These experimental results show that the CH₃ group of methanol doesn’t form hydrogen bonds with water molecules,and the red shift of C-H is affected by the hydrogen bond formation of C-O bond.The results of this paper are helpful to understand the physicochemical properties of aqueous solutions of DMSO,acetic acid,and methanol,and further advance related research on hydrogen bonding and solvation effects of these three types of organic molecular aqueous solutions in the related fields of life sciences and chemical synthesis.更多还原