Department of Physics, Sammilani Mahavidyalaya, E.M. Bypass, Baghajatin Station, Kolkata 700 075, India.
J Phys Chem A. 2013 Jun 13;117(23):4838-50. doi: 10.1021/jp404247v. Epub 2013 Jun 3.
The conformational preferences of the industrially significant ethyl propionate (EP) molecule have been investigated from the Raman and FTIR spectra, aided by ab initio and Car-Parrinello molecular dynamics (CPMD) simulation studies. The vibrational signatures of various rotameric forms of the EP molecule have been assigned for the first time from the potential energy distributions (PEDs). The critical analyses of the vibrational signatures reveal the coexistences of the Trans-Trans (TT), Trans-Antigauche (TG(-)) [Trans-Gauche (TG(+))], Antigauche-Trans (G(-)T) [Gauche-Trans (G(+)T)], Antigauche-Antigauche (G(-)G(-)) [Gauche-Gauche (G(+)G(+))], and Gauche-Antigauche (G(+)G(-)) [Antigauche-Gauche (G(-)G(+))] forms of the EP molecule at room and at high temperatures. However, at low temperature (ca. 70 °C), the TT and TG(-) forms of the EP molecule is estimated to be preponderant. The Car-Parrinello molecular dynamics simulation studies of the EP molecule estimated at high, room, and low temperatures are also in harmony with our conjecture as suggested from the vibrational analyses. The ab intio molecular dynamics simulations are observed to be a useful tool for the conformational analyses of the molecule.
工业上重要的丙酸乙酯（EP）分子的构象偏好已经通过拉曼和傅里叶变换红外光谱，并结合从头算和 Car-Parrinello 分子动力学（CPMD）模拟研究进行了研究。首次通过势能分布（PED）为 EP 分子的各种构象形式分配了振动特征。振动特征的关键分析揭示了 Trans-Trans（TT）、Trans-Antigauche（TG(-)）[Trans-Gauche（TG(+)）]、Antigauche-Trans（G(-)T）[Gauche-Trans（G(+)T）]、Antigauche-Antigauche（G(-)G(-)）[Gauche-Gauche（G(+)G(+)）]和 Gauche-Antigauche（G(+)G(-)）[Antigauche-Gauche（G(-)G(+)）]形式的 EP 分子在室温下和高温下共存。然而，在低温（约 70°C）下，EP 分子的 TT 和 TG(-)形式估计占主导地位。在高温、室温、低温下对 EP 分子进行的 Car-Parrinello 分子动力学模拟研究也与我们从振动分析中提出的假设一致。从头算分子动力学模拟被观察到是用于分子构象分析的有用工具。
