Studies on organophosphorus compounds 52.Structure-reactivity studies of organophosphorus compounds by MNDO calculations

MNDO and MM2(85)methods were used to study the conformation and the structure-reactivity relationship of neutral and acidic phosphorus esters.The calculation results indicate thatfor the most stable conformation,the charge density of phosphoryl oxygen(q_O)is determined notonly by the electronegativity of the substituents,but also by the conformation of the alkoxyl groupson the phosphorus atom.Meanwhile,the conformation of the alkoxyl group provides,as a rule,more important influence on the charge density of the phosphoryl oxygen.However,the energy ofthe highest occupied molecular orbital(EHOMO)is basically dependent on the eletronegativity of thesubstituents,while the donating ability or the withdrawing ability of the neutral phosphorus com-pounds is mainly governed by the EHOMO but not the q_O.This is also true for other kinds of theneutral oxygen-containing compounds.

Studies on organophosphorus compounds 52. Structure-reactivity studies of organophosphorus compounds by MNDO calculations

MNDO and MM2 (85) methods were used to study the conformation and the structure-reactivity relationship of neutral and acidic phosphorus esters. The calculation results indicate that for the most stable conformation, the charge density of phosphoryl oxygen (q_o) is determined not only by the electronegativity of the substituents, but also by the conformation of the alkoxyl groups on the phosphorus atom. Meanwhile, the conformation of the alkoxyl group provides, as a rule, more important influence on the charge density of the phosphoryl oxygen. However, the energy of the highest occupied molecular orbital (E_HOMO) is basically dependent on the eletronegativity of the substituents, while the donating ability or the withdrawing ability of the neutral phosphorus compounds is mainly governed by the E_HOMO but not the q_O. This is also true for other kinds of the neutral oxygen-containing compounds.