双环磷酸酯类化合物NMR结构效应研究

用现有理论说明不了双环磷酸酯类化合物³¹P 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³¹P化学位移变化的规律,同时还研究了它们的¹³C NMR化学位移和偶合常数的取代基效应。

STRUCTURAL EFFECTS ON NMR OF 4-SUBSTITUTED BICYCLIC PHOSPHATES

4-Substituted-2, 6, 7-trioxa-1-phosphabicyclo2.2.2] 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 δ_31P and I_p~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 σ_χ 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.