Conformational preferences and orbital interactions for methyl haloacetates

Autor(es)

Tormena, Claudio Francisco ^[1] ; Yoshinaga, Fabiana ; Doi, Telma R. ; Rittner, Roberto

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto. Departamento de Química - Brasil

• Tipo de documento: Artigo Científico
• Fonte: SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY; v. 63, n. 3, p. 511-517, Mar. 2006.
• Área do conhecimento: Ciências Exatas e da Terra - Química
• Assunto(s): Espectroscopia de ressonância magnética nuclear

Resumo

Conformational preferences and orbital interactions of methyl chloroacetate (1), methyl bromoacetate (2) and methyl iodo-acetate (3) were analyzed using experimental infra-red data, theoretical calculations and NBO analyses. The conformational equilibria of compounds 1-3 can be represented by their cis and gauche rotamers. The gauche form of 1 is stable in the vapour phase and in a non-polar solvent, but the cis is predominant in a polar solvent. For 2 the gauche form is more stable than the cis, in both the vapour and liquid phases, but for compound 3 only the gauche form was observed both in vapour phase as in solution. These conformational preferences were attributed to the orbital interaction between two antibonding orbitals pi(*)(C=O) -> sigma(*)(C-X). This unexpected interaction was possibly due to the high (0.2) electron density on pi(*)(C=O), which results from the interaction between ether oxygen lone pair and pi(*)(C=O). (AU)

• Processo FAPESP: 00/07692-5 - Estudos de equilíbrios conformacionais pela espectroscopia de ressonância magnética nuclear, espectroscopia no infravermelho e cálculos teóricos
• Beneficiário: Roberto Rittner Neto
• Modalidade de apoio: Auxílio à Pesquisa - Temático