Twelve heterocyclic ring compounds have been prepared and a high resolution Nuclear Magnetic Resonance study of each carried out. In particular, solvent effects and coupling constants have been studied. Some axial and equatorial shifts of methylene protons were found to be reversed compared to the predicted situation, Observed coupling constants have been found to be slightly solvent dependent. Some interesting values of coupling constants prompted a full X-ray crystal analysis of two of the compounds. This has been done, yielding bond lengths, bond angles, configuration around the phosphorus atom and conformation of the heterocyclic ring, all in the solid state. Dihedral angles for P-O-C-H systems have been calculated and an attempt has been made to correlate observed coupling constants with dihedral angles and electronegativity of substituents.