Tautomerism of N-acylphosphoramidic esters and N-acyl phosphinic amides

Summary

• 1. A series of halogen-substituted N-acylphosphorimidic esters and N-acyl phosphinimidic esters were prepared, and the dealkylation of these gave halogen-substituted N-acylphosphoramidic esters and N-acyl phosphinic amidies.

• 2. On the basis of the infrared spectra of the individual substances and their solutions in carbon tetrachloride, and also of pH data for their aqueous and aqueous-alcoholic solutions, it was concluded that halogen derivatives of N-acylphosphoramidic esters and N-acyl phosphinic amides have the amide form corresponding to the tautomeric form (a) or that the tautomeric equilibrium of these substances is displaced toward the form (a).

• 3. The frequency of the valence vibration of the NH group may be displaced to about 2600 cm⁻¹ when it is strongly hydrogen-bonded to the P=O group of phosphine oxides.