Unexpected Conformational Properties of 1-Trifluoromethyl-1-Silacyclohexane, C5H10SiHCF3: Gas Electron Diffraction, Low-Temperature NMR Spectropic Studies, and Quantum Chemical Calculations
作者:Georgiy V. Girichev、Nina I. Giricheva、Andras Bodi、Palmar I. Gudnason、Sigridur Jonsdottir、Agust Kvaran、Ingvar Arnason、Heinz Oberhammer
DOI:10.1002/chem.200600683
日期:2007.2.12
species was investigated by means of gas electron diffraction (GED), dynamic nuclear magnetic resonance (DNMR) spectroscopy, and quantum chemical calculations (B3LYP, MP2, and CBS-QB3). According to GED, the compound exists as a mixture of two Cs symmetry conformers possessing the chair conformation of the six-membered ring and differing in the axial or equatorial position of the CF3 group (axial=58(12)
通过气体电子衍射(GED),动态核磁共振(DNMR)光谱研究了1-三氟甲基-1-硅环己烷(C5H10SiHCF3)的轴向和赤道构象异构体的分子结构,以及这些物种之间的热力学平衡。 ,以及量子化学计算(B3LYP,MP2和CBS-QB3)。根据GED的说法,该化合物以两个Cs对称构象异构体的混合物形式存在,这些构象具有六元环的椅子构象,并且在CF3基团的轴向或赤道位置上有所不同(轴向= 58(12)mol%/赤道= 42 (12)mol%)在T = 293K。该结果与理论预测良好吻合。然而,这与环己烷类似物的构象性质形成鲜明对比。两个构象异构体的主要结构特征是异常长的环外键长Si--C 1.934(10)A.低温19F NMR实验得出的轴向/赤道比为17(2)mol%:83(2)摩尔%在113 K和DeltaG(不相等)为5.5(2)kcal mol-1。使用PCM(B3LYP / 6-311G