Ab Initio Structures of Phosphorus Acids and Esters. 3. P-O-P Bridged Compounds H4P2O2n-1 for n = 1 to 4

摘要

The detailed molecular structures including the equilibrium conformations and energies of the four prototype phosphorus compounds exhibiting a phosphorus oxygen phosphorous(P-O-P) interconnection, H4P2O2n-1 for n=1 to 4, were determined by ab initio quantum chemical calculations. The size, bending force constant, and barrier to linearity of the P-O-P angle were investigated for the n=1 to 3 species and found to be consistent with the large (up to 180) angles seen in pyrophosphate salts. The enthalpies and free energies of the hydrolysis reactions, replacing P-O-P linkage with two P-O-H groups to form the monoacids, were found to increase slightly with increasing numbers of substituents, being positive or close to zero in the gas phase.