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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Proton Spin-Spin Coupling and Electron Delocalization
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Proton Spin-Spin Coupling and Electron Delocalization

机译：质子自旋自旋耦合和电子离域

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摘要

The spin-spin coupling of protons measured by the constant J_(HH') in NMR experiments is dominated by a term proportional to the product of the electron spin densities at the tow nuclei, the Fermi contact term. The probability of β electrons being in excess over α electrons at the position of nucleus n', given that there is an α electron at n, is proportional to the negative of the exchange density, the total Fermi correlation between n and n'. thus the delocalization of the Fermi hole between n and n' is the mechanism whereby the spin perturbation caused by the magnetic interaction of an electron with nucleus n is transmitted to n'. The density and exchange density within the basin of a hydrogen atom are described primarily in terms of s-type basis functions, and one may approximate the exchange density between two protons at n and n' by the exchange between the two associated atomic basins determined by the delocalization index δ(A,B) within the quantum theory of atoms in molecules. It is shown that this model yields good linear regression equations relating J_(HH') to δ(H,H') for hydrogen atoms bonded to different carbons in alkanes, alkenes, their cyclic congeners, and polybenzenoid hydrocarbons.
机译：在NMR实验中，通过常数J_（HH'）测得的质子的自旋-自旋偶合主要受一个与丝束核上电子自旋密度乘积（费米接触项）成比例的术语所致。假定在n'处有一个α电子，则在原子n'处，β电子超过α电子的概率与交换密度的负数成正比，n和n'之间的总费米相关性。因此，费米空穴在n和n'之间的离域是一种机制，通过该机制，电子与原子核n的磁相互作用引起的自旋扰动被传递到n'。氢原子盆内的密度和交换密度主要是根据s型基函数描述的，并且可以通过以下公式确定两个相关原子盆之间的交换，近似得出n和n'处两个质子之间的交换密度。分子原子理论中的离域指数δ（A，B）。结果表明，对于与烷烃，烯烃，其环状同源物和聚苯并碳氢化合物中的不同碳原子键合的氢原子，该模型产生了良好的线性回归方程，将J_（HH'）与δ（H，H'）关联。

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