Magnetic non-equivalence in organophosphorus esters

Abstract

The ¹H n.m.r. spectra of a number of esters of phosphoric, phosphonic, phosphorothioic, phosphonothioic, phosphorodithioic, and phosphonodithioic acids are reported. In certain cases the methylene protons of the ethoxygroups show non-equivalence and such spectra are analysed by full iterative calculations using the LAOCN 3 program. The effects of temperature and solvent changes on the non-equivalence are reported and the results are interpreted in terms of intrinsic non-equivalence (due to an asymmetric phosphorus atom) or unequal conformer populations or a combination of both factors.