Coherent Light and Atomic and Molecular Spectroscopy Laboratory, College of Physics, Jilin University, Changchun 130012, China.
Coherent Light and Atomic and Molecular Spectroscopy Laboratory, College of Physics, Jilin University, Changchun 130012, China; Key Laboratory of Physics and Technology for Advanced Batteries, College of Physics, Jilin University, Changchun 130012, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2019 Apr 15;213:463-466. doi: 10.1016/j.saa.2018.08.029. Epub 2018 Aug 17.
Raman spectra of acetic acid-water binary solutions with different concentrations have been measured in order to study molecular association of acetic acid. We find that the symmetric and asymmetric OH stretching vibration of water (3242 and 3443 cm) have marked changes of Raman shift when the volume fraction of acetic acid (V) is 0.3 and 0.8, respectively, which demonstrates that the hydrogen bonding of the water is affected, causing association molecule (acetic acid-water structure) to undergo two phase transitions. Furthermore, the peak of the HCH bending vibration is blue-shifted at V = 0.8, which shows that the acetic acid-acetic acid structure undergoes a phase transition and the acetic acid side-on dimer is formed. These results also indicate that the CH vibration mode in CH⋯O is HCH bending vibration. Finally, the phase transition process of association molecules (hydrated monomer, linear dimer, acetic acid side-on dimer and water-separated dimer) has been obtained in acetic acid-water binary solutions through theoretical analysis.
为了研究乙酸的分子缔合，我们测量了不同浓度的乙酸-水二元溶液的拉曼光谱。我们发现，当乙酸的体积分数（V）分别为 0.3 和 0.8 时，水的对称和不对称 OH 伸缩振动（3242 和 3443 cm）的拉曼位移有明显变化，这表明水的氢键受到影响，导致缔合分子（乙酸-水结构）发生两相转变。此外，在 V=0.8 时，HCH 弯曲振动的峰发生蓝移，这表明乙酸-乙酸结构发生了相变，形成了乙酸侧对二聚体。这些结果还表明，CH⋯O 中的 CH 振动模式是 HCH 弯曲振动。最后，通过理论分析，我们得到了在乙酸-水二元溶液中缔合分子（水合单体、线性二聚体、乙酸侧对二聚体和水分离二聚体）的相变过程。
