Dutta Bipan, Tanaka Takeyuki, Chowdhury Joydeep
†Department of Physics, Sammilani Mahavidyalaya, E. M. Bypass, Baghajatin Station, Kolkata 700094, India.
‡Integrated Centre of Science, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan.
J Phys Chem A. 2015 Jul 23;119(29):8062-75. doi: 10.1021/acs.jpca.5b03486. Epub 2015 Jul 14.
The conformational preferences of the industrially and biologically significant propyl acetate (PA) molecule have been investigated by Raman and FTIR spectra, aided by ab initio and Car-Parrinello molecular dynamics (CPMD) simulation studies. The PA molecule can exist in various rotameric forms at room temperature, trans-trans [TT], trans-gauche [(TG(+))/(TG(-))], gauche-trans [(G(+)T)/(G(-)T)], and gauche-gauche [(G(+)G(-))/(G(-)G(+))], depending upon the rotation about the O3-C4 and C4-C5 bonds of the molecule. The vibrational signatures of different rotameric forms of the PA molecule have been assigned for the first time. Raman and temperature-dependent FTIR spectra of the PA molecule envisage the coexistence of the TT, TG(+)/TG(-), G(+)T/G(-)T, and G(+)G(-)/G(-)G(+) forms of the PA molecule at room temperature. However, at low (ca. -95 °C) and high temperatures (ca. 65 °C), the TG(+) form of the PA molecule is estimated to be preponderant. These results are substantiated by the CPMD simulations, together with the estimation of fwhm values of the vibrational signatures of the PA molecule recorded at high-, room-, and low-temperature domains.
借助从头算和Car-Parrinello分子动力学（CPMD）模拟研究，通过拉曼光谱和傅里叶变换红外光谱（FTIR）对工业和生物学上具有重要意义的乙酸丙酯（PA）分子的构象偏好进行了研究。PA分子在室温下可以以各种旋转异构体形式存在，反式-反式[TT]、反式-顺式[(TG(+))/(TG(-))]、顺式-反式[(G(+)T)/(G(-)T)]和顺式-顺式[(G(+)G(-))/(G(-)G(+))]，这取决于分子中O3-C4和C4-C5键的旋转。首次确定了PA分子不同旋转异构体形式的振动特征。PA分子的拉曼光谱和温度依赖的FTIR光谱表明，在室温下，PA分子的TT、TG(+)/TG(-)、G(+)T/G(-)T和G(+)G(-)/G(-)G(+)形式共存。然而，在低温（约-95°C）和高温（约65°C）下，估计PA分子的TG(+)形式占主导。这些结果通过CPMD模拟得到证实，同时还估计了在高温、室温及低温区域记录的PA分子振动特征的半高宽值。
