Of Ph <sub> 3 </ Sub> Px <sub> 2 </ Sub> Class Molecular Structure And Phosphine Acyl Nitrile Oxide And Acrylonitrile Reaction Mechanism Studies

Quantum chemistry have been developed rapidly in the past decade, many theoretical and computational methods were formulated. Presently, Hartree-Fock(HF) and Post HF, semi-empirical and density functional theory(DFT) have become essential tools used in quantum calculations. In order to solve the coulomb correlation problem neglected by the traditional ab initio methds, the DFT focuses its attention to the electron density, not many-body wave function, the ground state energy of system was expressed as a functional of electron density. In this these, DFT was employed to carry out calculations for two theoretical problem, One is investigation of optimization and solvent effect. The other is investigation of reaction mechanism and transition state. This research is described as follows:Chapter1 introduced the basis and background of our studies which offer us with useful and reliable quantum methods.In Chapter2, structure of Ph₃PCl₂ was optimized at PW91/DZVP level. Two stationary structures were obtained which have no imaginary. They are trigonal bipyamidal structure and ionic structure. In the meantime their geometry parameters, atomic charge were presented. The solvent effect was studied with cluster model of discrete water molecule and Onsager reaction field model. Because the oxygen atom of water molecule can attack on phosphorus to form P=O bond, Ph₃PCl₂ could not co-exist with water molecule. Its two structures were stabilized by acetonitrile and benzene solvent.In Chapter3, the structure of Ph₃PF₂ and Ph₃PI₂ were optimized respectively by using B3LYP/6-31g and B3LYP/3-21g. The two stationary structures of Ph₃PF₂ were obtained. One was trigonal bipyamidal structure, the other was ionic structure. The three stationary structures of Ph₃PI₂ were obtained. The structure of Ph₃PX₂ molecule were summarized in order to find regular.In Chapter4, the reaction mechanism of phosphonyl nitrie oxides with acrylonitrile has been investigated. In order to facilitate calculations, we use methyl instead ofpropyl. The transition states of the reaction were hypothesized and found using TS method. The vibration analysis and the IRC analysis testified the authenticity of intermediate and transition states. The result showed that the reaction has two transition states and was completed in two steps. The geometries and harmonic frequencies of reactants, intermediate, transition states and products have been calculated at the B3LYP/6-31G(d, p) level, then the energy of these structure were obtained. Finally the activation energy of reaction was calculated.