乙酸甲酯的二聚体结构

Dimer structure of methyl acetate

乙酸甲酯中C=O伸缩振动频率在红外光谱和拉曼光谱中存在较大差异,猜测是由乙酸甲酯的非重合效应所导致,通过二聚体结构来进行解释。利用密度泛函理论(Density functional theory,DFT)对二聚体结构进行计算,通过浓度稀释实验采集乙酸甲酯/CCl_(4)二元体系中C=O伸缩振动的偏振拉曼光谱,结合二聚体结构分析C=O伸缩振动的浓度效应。结果表明:乙酸甲酯二聚体结构的DFT计算结果与红外、拉曼的光谱相吻合;在偏振拉曼光谱中,各向同性和各向异性拉曼的C=O伸缩振动频率在高浓度时存在差异,随着乙酸甲酯浓度降低,各向异性和各向同性拉曼的C=O伸缩振动频率均往高波数移动,同时两者的频率差逐渐减小。该文提出的二聚体结构可合理地解释C=O伸缩振动的浓度效应,这对液体分子聚集态结构的研究具有参考意义。

In order to study the phenomenon of large difference of C=O stretching vibration frequency of methyl acetate between infrared spectrum and Raman spectrum,we supposed that this was caused by the non-coincident effect of methyl acetate,and the dimer structure was proposed to explain this phenomenon.The dimer structure was calculated by density functional theory(DFT)and the polarized Raman spectrum of C=O stretching vibration in the methyl acetate/CCl_(4) binary system was collected by concentration dilution experiments.The concentration effect of C=O stretching vibration was analyzed by the dimer structure.The results indicated that the DFT calculation results of the dimer structure of methyl acetate were consistent with infrared spectrum and Raman spectrum.In polarized Raman spectrum,the C=O stretching vibration frequencies of isotropic and anisotropic Raman were different at high concentrations,and with the decrease of the concentration of methyl acetate, C=O stretching vibration frequencies of anisotropic and isotropic Raman moved towards high wave numbers,and the frequency difference between the two gradually decreased.The dimer model proposed in this paper has reasonably explained the concentration effect of C=O stretching vibration,which is of reference significance for the research of the aggregation structure of liquid molecules.