Ab initio studies on organophosphorus compounds. Part 2. Monoanionic methyl methylphosphonate and methyl methylphosphinate and their sulfur analogues

Abstract

The molecular properties of nine monoanionic methyl methylphosphonate and methyl methylphosphinate and their sulfur analogues have been studied by ab initio molecular orbital methods. Molecular structures, dipole moments, stability, charge distributions and torsional barriers have been reported. The effects of sulfur and oxygen substitution have been compared. Energetics for model and hydrolysis reactions have been calculated for all the compounds up to the MP2/6-31G*//6-31G* level. Phosphonate compounds with –OCH₃ group were found to adopt an extended molecular backbone while –SCH₃ systems preferred bent conformations. Inclusion of the correlation corrections with 6-31 G* basis set, instead of 3-21G(*) level, was found to have an effect on the calculated energetics of model reactions.