Modeling Vibrational Spectra of Ester Carbonyl Stretch in Water and DMSO Based on Molecular Dynamics Simulation

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• 作者：Bin Fang ; Tianjun Wang ; Xian Chen ; Tan Jin ; Ruiting Zhang ; Wei Zhuang
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：September 24, 2015
• 年：2015
• 卷：119
• 期：38
• 页码：12390-12396
• 全文大小：476K
• ISSN：1520-5207

文摘

On the basis of molecular dynamics simulation, we model the ester carbonyl stretch FTIR signals of methyl acetate in D₂O and DMSO. An ab initio map is constructed at the B3LYP/6-311++G** level to relate the carbonyl stretch frequency to the external electric field. Using this map, fluctuating Hamiltonian of the carbonyl stretch is constructed from the MD simulation trajectory. The IR spectra calculated based on this Hamiltonian are found to be in good agreement with the experiment. For methyl acetate in D₂O, hydrogen bonding on alkoxy oxygen causes a blue shift of frequency, while that on carbonyl oxygen causes a red shift. Two peaks observed in FTIR signals originate from the balance of these two effects. Furthermore, in both D₂O and DMSO solutions, correlations are found between the instantaneous electric field on C鈺怬 and the frequencies. Broader line width of the signal in D₂O suggests a more inhomogeneous electric field distribution due to the complicated hydrogen-bonding environment.