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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Visualization and quantification of the anisotropic effect of C=C double bonds on H-1 NMR spectra of highly congested hydrocarbons-indirect estimates of steric strain
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Visualization and quantification of the anisotropic effect of C=C double bonds on H-1 NMR spectra of highly congested hydrocarbons-indirect estimates of steric strain

机译：C = C双键对高度拥挤烃的H-1 NMR光谱的各向异性效应的可视化和量化-空间应变的间接估计

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摘要

The anisotropic effect of the olefinic C=C double bond has been calculated by employing the NICS (nucleus independent chemical shift) concept and visualized as an anisotropic cone by a through space NMR shielding grid. Sign and size of this spatial effect on H-1 chemical shifts of protons in norbornene, exo- and endo-2-methylnorbornenes, and in three highly congested tetracyclic norbornene analogs have been compared with the experimental H-1 NMR spectra as far as published. H-1 NMR spectra have also been calculated at the HF/6-31G* level of theory to get a full, comparable set of proton chemical shifts. Differences between delta(H-1)/ppm and the calculated anisotropic effect of the C=C double. bond are discussed in terms of the steric compression that occurs in the compounds studied.
机译：烯烃C = C双键的各向异性效应已通过采用NICS（与核无关的化学位移）概念进行了计算，并通过空间NMR屏蔽网格可视化为各向异性锥。迄今为止，该空间效应对降冰片烯，外-和内-2-甲基降冰片烯以及三个高度拥挤的四环降冰片烯类似物中质子的H-1化学位移的空间效应的符号和大小已与实验的H-1 NMR光谱进行了比较。 。还已经在理论的HF / 6-31G *水平上计算了H-1 NMR光谱，以获得一套完整的，可比较的质子化学位移。 delta（H-1）/ ppm与计算得出的C = C double的各向异性效应之间的差异。根据所研究化合物中发生的空间压缩来讨论键。

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