Conformational preferences for N,N-dimethyl-2-haloacetamides (halo= F, Cl, Br and I) through theoretical and experimental studies: An unexpected orbital interaction

Autor(es)

Martins, Carina R. ; Rittner, Roberto ; Tormena, Claudio Francisco ^[3]

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM; v. 728, n. 1/3, p. 79-84, Sept. 2005.
• Área do conhecimento: Ciências Exatas e da Terra - Química
• Assunto(s): Espectroscopia infravermelha

Resumo

Conformational preferences and orbital interactions of N,N-dimethyl-2-fluoroacetamide (1), N,N-dimethyl-2-chloroacetamide (2), N,Ndimethyl-2-bromoacetamide (3) and N,N-dimethyl-2-iodoacetamide (4) were analyzed using experimental infra-red data, theoretical calculations and NBO analysis. The conformational equilibria of compounds 1-4 can be represented by their cis and gauche rotamers. The gauche form of I is stable in the vapor phase and in a non-polar solvent, but the cis is predominant in a polar solvent. For 2-4 the gauche form is more stable than the cis, in both the vapor and liquid phases. 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 (0.3) electron density on pi*C=O, which results from the interaction between one nitrogen 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
• Processo FAPESP: 02/12305-6 - Estudos dos efeitos estereoeletrônicos em equilíbrios conformacionais e nos parâmetros de RMN (delta e j), através de dados experimentais e calculados
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores