Change in the reactivity and spectral characteristics from phosphoryl to thionephosphoryl compounds

Abstract

1. It was demonstrated experimentally that, in contrast to the existing premise, the replacement of oxygen in phosphorus derivatives by sulfur, both in the alkoxyl and in the phosphoryl groups, leads to an increase in the deficit of electron density on the phosphorus atom of the molecules in the ground state. The decrease in the reactivity in reactions of nucleophilic substitution of thionephosphoryl compounds is due chiefly to different polarizabilities of P=O and P=S compounds, the influence of solvation, steric and other factors. 2. The conjugation of the substituents with the 3d-orbitals of the phosphorus atom, manifested statically and reflected in the spectral characteristics of organophosphorus compounds, is weakened in the case of nucleophilic attack, and in the transition state the electron density on the phosphorus atom is determined to a great degree by the inductive influence of the substituents.