Hangzhou Institute of Advanced Studies, College of chemistry and life sciences, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
Department of Chemistry, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, China.
Phys Chem Chem Phys. 2023 Jul 12;25(27):18048-18055. doi: 10.1039/d3cp01876h.
In this study, polarization Raman spectra were collected for binary mixtures of formic acid/methanol and formic acid/acetonitrile with different volume fractions. The broad band of formic acid in the CO vibration region was divided into four vibration peaks, corresponding to CO symmetric and anti-symmetric stretching vibration from cyclic dimer, CO stretching from open dimer, and CO stretching from the free monomer. The experiments showed that as the volume fraction of formic acid in the binary mixture decreased, the cyclic dimer gradually converted to the open dimer, and at a volume fraction of 0.1, fully depolymerized into monomer form (free monomer, solvated monomer, and hydrogen bonding monomer clusters with solvent). The contribution percentage of the total CO stretching intensity of each structure at different concentrations was quantitatively calculated using high resolution infrared spectroscopy, and the results were consistent with the conclusions predicted by polarization Raman spectroscopy. Concentration-triggered 2D-COS synchronous and asynchronous spectra also confirmed the kinetics of formic acid diluted in acetonitrile. This work provides a spectroscopic method for studying the structure of organic compounds in solution and concentration-triggering kinetics in mixtures.
在这项研究中，我们收集了甲酸/甲醇和甲酸/乙腈二元混合物在不同体积分数下的偏振拉曼光谱。甲酸在 C-O 振动区域的宽带被分为四个振动峰，分别对应于环状二聚体的 C-O 对称和反对称伸缩振动、开二聚体的 C-O 伸缩振动以及自由单体的 C-O 伸缩振动。实验表明，随着二元混合物中甲酸体积分数的降低，环状二聚体逐渐转化为开二聚体，在体积分数为 0.1 时，完全解聚成单体形式（自由单体、溶剂化单体和与溶剂形成氢键的单体簇）。使用高分辨率红外光谱定量计算了不同浓度下每种结构的总 C-O 伸缩强度的贡献百分比，结果与偏振拉曼光谱预测的结论一致。浓度触发的 2D-COS 同步和异步光谱也证实了甲酸在乙腈中的稀释动力学。这项工作为研究溶液中有机化合物的结构和混合物中浓度触发动力学提供了一种光谱方法。
