Valence‐Bond Calculation of Geminal Spin‐Spin Coupling Constants in Substituted Methanes
Valence‐Bond Calculation of Geminal Spin‐Spin Coupling Constants in Substituted Methanes
复制标题
取代甲烷中孪生自旋-自旋耦合常数的价键计算
DOI：
10.1063/1.1732827
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发表时间：
1962
期刊：
影响因子：
--
通讯作者：
D. Grant
中科院分区：
文献类型：
--
作者：
M. Barfield;D. Grant
对一类取代甲烷的偕质子自旋-自旋耦合常数进行了理论研究。使用价键方法和六电子模型，由亚甲基和相邻的π电子对组成，计算超共轭能和接触对孪晶耦合常数的贡献。这些数据与实验结果一致，表明超共轭效应给出的耦合常数比仅根据H-C-H角依赖性所预期的要大。这被证明是产生的离域结构，在基态相关的双子质子的自旋。值得注意的是，孪晶耦合常数取决于亚甲基相对于相邻π电子系统的取向，并且该数据是针对两个C-C核间距值报告的。
A theoretical study is presented of geminal proton spin‐spin coupling constants for a class of substituted methanes. Using a valence‐bond approach and a six electron model, consisting of a methylene group with an adjacent π electron pair, the hyperconjugation energy and the contact contribution to the geminal coupling constant are calculated. These data, which are in agreement with the experimental findings, indicate that hyperconjugative effects give larger coupling constants than would be expected on the basis of the H–C–H angular dependence alone. This is shown to arise out of delocalized structures, which in the ground state correlate the spins of the geminal protons. It is noted that the geminal coupling constant depends on the orientation of the methylene group with respect to the adjacent π electron system, and this data is reported for two values of the C–C internuclear distance.