Estudos em estruturas e reatividade de reações Sn2

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

The gas phase reactions of the HO, NC and HCC anions with the methyl fluoride by the bimolecular nucleofilic substitution mechanism (SN2) was caracterized by ab initio calculations using basis sets of (9s6p1d/4s1p) [4s3p1d/2s1p] leveI. Eletronic correlation energy was included using up to fourth order MøIIer-Plesset perturbation theory. The importance of species related to proton transfer channel in the study of the reactivity of these systems was discussed. The RRKM unimolecular reaction theory was employed to estimate the reaction efficienceis. The theoretical parameters obtained from the reaction coordinate characterization were used for the calculation of the efficiencies. A satifactorily agreement with the experimental results was observed. In order to find the origin of the reaction barrier, we analysed the behaviour of the total energy and its components along the reaction coordinate. The contribution of the molecular orbitals of each species to the behaviour of the system was examinated to identify possible effects related with frontier orbital interaction and charge transfer. The realibility of AM1 and MNDO/PM3 semiempirical methods in the study of this reaction mechanism was evaluated comparing the semiempirical results with the ab initio ones. It was found that there are substancial differences between them. We proposed some possible factors responsable for the results behaviour. Suggestions of application of these methodos were presented.

ASSUNTO(S)

fisico-quimica quimica organica

ACESSO AO ARTIGO

Documentos Relacionados