双环磷酸酯类化合物NMR结构效应研究

STRUCTURAL EFFECTS ON NMR OF 4-SUBSTITUTED BICYCLIC PHOSPHATES

用现有理论说明不了双环磷酸酯类化合物^(31)P NMR化学位移的变化。本文在我们提出的核外电子云球对称效应原理基础上,用量子化学和分子力学计算的参数,表达了这类化合物^(31)P化学位移变化的规律,同时还研究了它们的^(13)C NMR化学位移和偶合常数的取代基效应。

4-Substituted-2, 6, 7-trioxa-1-phosphabicyclo [2.2.2] octane-1-oxides (A) (simpled as bicyclic phosphates) are potent convulsants in mamals, and were treated as a research model of polar substituent effects in physical organic chemistry. Their 31P NMR can't be explained on the basis of the chemical theory available today. The 31P chemical shifts of compounds (A) exhibit an increasing upfield trend as the electron-withdrawing properties of the substituent X become greater and a reasonable correlation between δ31P and lp_o (bond length), △q (charge distribution) is obtained. 13C NMR of compounds (A) were also determined. A good relationship between 13C -4 chemical shifts and Taft inductive parameters σx was also established. Substitueut effects on 3J coupling constant were studied. 31P and 13C NMR chemical shifts are explained by our new principle of the spherical symmetry of the electron cloud around the resonant nucleus.