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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformational Stability from Rare Gas Solutions, r(0) Structural Parameters, Barriers to Internal Rotation, and Ab initio Calculations for Vinyl Silyl Fluoride
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Conformational Stability from Rare Gas Solutions, r(0) Structural Parameters, Barriers to Internal Rotation, and Ab initio Calculations for Vinyl Silyl Fluoride

机译：稀有气体溶液的构象稳定性，r（0）结构参数，内部旋转的障碍以及乙烯基氟硅烷的从头算

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摘要

The Raman (3300-10 cm(-1)) and infrared (3300-40 cm(-1)) spectra of gaseous and solid vinyl silyl fluoride, CH2=CHSiH2F, have been recorded. Raman spectrum of the liquid has also been recorded and depolarization values obtained. Variable-temperature studies of the infrared spectra of the sample dissolved in liquid krypton (-110 to -150 degrees C) and liquid xenon (-60 to -100 degrees C) have been carried out. From these studies, the enthalpy difference has been determined to be 76 +/- 7 cm(-1) (0.91 +/- 0.08 kJ/mol) from the krypton solutions and 69 +/- 7 cm(-1) (0.82 +/- 0.08 kJ/mol) from the xenon solutions, with the gauche conformer the more stable form. From the far-infrared spectrum of the gas, the asymmetric torsional fundamentals for the cis and gauche conformers have been observed at 102.34 and 86.56 cm(-1), respectively, with each having several "hot bands" failing to lower frequencies. From these frequencies along with the experimentally determined conformational enthalpy difference, as well as the gauche skeletal dihedral angle, the potential function governing the conformational interchange has been determined with the following Fourier cosine potential coefficients: V-1 = -80 +/- 11, V-2 = -42 +/- 15, V-3 = 622 +/- 5, V-4 = 34 +/- 5, and V-6 = -31 +/- 2 cm(-1). The gauche-to-cis and gauche-to-gauche barriers are 664 cm(-1) (7.94 kJ/mol) and 608 cm(-1) (7.27 kJ/mol), respectively. Complete vibrational assignments are provided for both conformers. In addition, equilibrium geometries and electronic energies have been determined for both rotamers from ab initio calculations using restricted Hartree-Fock and Moller-Plesset perturbation method to the second order (MP2), as well as density functional theory by the B3LYP methods, employing a number of basis sets up to 6-311+G(2df,2pd). All levels of calculation predict the gauche conformer to be the more stable form. By systematically adjusting the ab initio predicted structural values to fit the previously reported microwave rotational constants, adjusted r(0) parameters have been obtained for both conformers. These values are compared to those for the corresponding chloride and methyl compounds. The spectroscopic and theoretical results are discussed and compared to the corresponding quantities for some similar molecules.
机译：记录了气态和固态乙烯基甲硅烷基氟的拉曼光谱（3300-10 cm（-1））和红外光谱（3300-40 cm（-1）），CH2 = CHSiH2F。还记录了液体的拉曼光谱并获得了去极化值。已对溶解在液态k（-​​110至-150℃）和液态氙（-60至-100℃）中的样品的红外光谱进行了可变温度研究。根据这些研究，从k溶液确定的焓差为76 +/- 7 cm（-1）（0.91 +/- 0.08 kJ / mol）和69 +/- 7 cm（-1）（0.82 + （-0.08 kJ / mol）的氙气溶液，具有gauche构象异构体的更稳定形式。从气体的远红外光谱中，分别在102.34和86.56 cm（-1）处观察到顺式和gauche构象异构体的不对称扭转基本原理，每个都有几个“热带”，无法降低频率。根据这些频率以及实验确定的构象焓差以及gauche骨架二面角，已经确定了控制构象互换的势函数，其傅立叶余弦势系数如下：V-1 = -80 +/- 11 V-2 = -42 +/- 15，V-3 = 622 +/- 5，V-4 = 34 +/- 5和V-6 = -31 +/- 2 cm（-1）。 gauche-to-cis和gauche-to-gauche势垒分别为664 cm（-1）（7.94 kJ / mol）和608 cm（-1）（7.27 kJ / mol）。为这两个合格者提供了完整的振动分配。此外，还通过使用限制的Hartree-Fock和Moller-Plesset摄动法至二阶（MP2）以及从B3LYP方法获得的密度泛函理论，通过从头算计算，确定了两种旋转异构体的平衡几何形状和电子能量。基数设置为6-311 + G（2df，2pd）。所有级别的计算都预测gauche构型将是更稳定的形式。通过系统地调整从头算起的预测结构值以适应以前报告的微波旋转常数，已为两个构象体获得了调整后的r（0）参数。将这些值与相应的氯化物和甲基化合物的值进行比较。讨论了光谱和理论结果，并将其与一些相似分子的相应量进行了比较。

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