Influence of protonic solvents on spin–spin coupling involving phosphorus directly bonded to hydrogen, fluorine, or another phosphorus atom in phosphoryl and thiophosphoryl molecules

Abstract

The effect on the n.m.r. spectral parameters of dissolving five different phosphoryl and thiophosphoryl compounds in a series of organic solvents of varying protonic acidity was studied. For all five of these compounds, the absolute magnitudes of the coupling constants for the directly bonded magnetically active nuclei increased with solvent acidity, whilst there was also a concurrent small change in the chemical shift(s). These and related results are discussed in terms of association with the acidic solvent through hydrogen bonding at the phosphoryl oxygen atom (or thiophosphoryl sulphur atom). Some pertinent semi-empirical LCAO–MO–SCF calculations have been carried out for these molecules, with and without hydrogen bonding.