Stereoelectronic effect in reactions of phosphoester bond rupture

The potential surface profile of the interaction of the anion (CH₃O)₂PO₂ ^– with the nucleophile CH₃O^– in the gas phase and in aqueous solution has been calculated by the AMl method. The energy of the transition state of the reaction in the gas phase is very much dependent on the position of the equatorial methoxy group; the change in the activation barrier amounts to 6 kcal/mole. The stereoelectronic effect is due to electrostatic interaction of the dipole moment of the equatorial substituent with the charge of the attacking or leaving group. An accounting for solvation gives a considerable decrease in the stereoelectronic effect.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2528–2532, November, 1990.