Theoretical and Experimental Investigation on the Rotational Isomerism in alpha-Fluoroacetophenones

Autor(es)

Fiorin, Barbara C. ^[1] ; Basso, Ernani A. ^[2] ; Tormena, Claudio F. ^[3] ; Rittner, Roberto ^[3] ; Abraham, Raymond J. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Estadual Ponta Grossa, Dept Quim, BR-84030900 Ponta Grossa, PR - Brazil

^[2] Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana - Brazil

^[3] State Univ Campinas UNICAMP, Inst Chem, Phys Organ Chem Lab, BR-13083862 Campinas, SP - Brazil

^[4] Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside - England

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry A; v. 113, n. 12, p. 2906-2913, MAR 26 2009.
• Citações Web of Science: 7

Resumo

The geometries involved in the conformational equilibria of alpha-fluoroacetophenone, p-nitro-alpha-fluoroacetophenone, and p-methoxy-alpha-fluoroacetophenone were investigated. Theoretical calculations showed that cis and gauche forms (F-C-C=O) are their most stable conformers and that in the vapor phase the gauche conformer is predominant. The three compounds were synthesized, and the conformational behavior in solution was estimated from infrared (IR) and nuclear magnetic resonance (NMR) spectra obtained in solvents of different polarity. Their IR spectra showed one carbonyl absorption for the cis and one for the gauche conformer, and that the cis conformer was preferred in the more polar solvents. (1)J(CF), (2)J(C(O)F), and (2)J(HF) coupling constants were obtained from their NMR spectra, and they also showed a preference for the cis conformer when more polar solvents were used. The vapor phase calculations showed a conformational preference for the gauche form. However, when the solvent effects were included in the calculations, the results were in complete agreement with the experimental data (NMR and IR), the cis conformer being the most stable one. (AU)

• Processo FAPESP: 05/59649-0 - Estudos de estrutura eletrônica e molecular através de métodos espectroscópicos e cálculos teóricos
• Beneficiário: Roberto Rittner Neto
• Modalidade de apoio: Auxílio à Pesquisa - Temático