Abstract: 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 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.

Key words: Bicyclic phosphates, ³¹P NMR, ¹³C NMR, Coupling constants, Calculation of chemical shifts, Combined calculation of MM2-MNDO, Substituent effects