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Type: Artigo de periódico
Title: Studies On The S-cis-trans Isomerism For Some Furan Derivatives Through Ir And Nmr Spectroscopies And Theoretical Calculations.
Author: Rittner, Roberto
Ducati, Lucas C
Tormena, Cláudio F
Cormanich, Rodrigo A
Fiorin, Barbara C
Braga, Carolyne B
Abraham, Raymond J
Abstract: The s-cis-trans isomerism of two furan derivatives [2-acetyl- (AF) and 2-acetyl-5-methylfuran, (AMF)] was analyzed, using data from the deconvolution of their carbonyl absorption band in two solvents (CH(2)Cl(2) and CH(3)CN). These infrared data showed that the O,O-trans conformers predominate in the less polar solvent (CH(2)Cl(2)), but these equilibria change in a more polar solvent (CH(3)CN) leading to a slight predominance of the O,O-cis conformers, in agreement with the theoretical calculations. The later results were obtained using B3LYP-IEFPCM/6-31++g(3df,3p) level of theory, which taking into account the solvent effects at IEFPCM (Integral Equation Formalism Polarizable Continuum Model). Low temperature (13)CNMR spectra in CD(2)Cl(2) (ca. -75 °C) showed pairs of signals for each carbon, due to the known high energy barrier for the cis-trans interconversion leading to a large predominance of the trans isomers, which decreases in acetone-d(6). This was confirmed by their (1)HNMR spectra at the same temperatures. Moreover, despite the larger hyperconjugative interactions for the O,O-cis isomers, obtained from NBO data, these isomers are destabilized by the their Lewis energy.
Subject: Acetylation
Magnetic Resonance Spectroscopy
Molecular Conformation
Spectroscopy, Fourier Transform Infrared
Citation: Spectrochimica Acta. Part A, Molecular And Biomolecular Spectroscopy. v. 103, p. 84-9, 2013-Feb.
Rights: fechado
Identifier DOI: 10.1016/j.saa.2012.11.013
Date Issue: 2013
Appears in Collections:Unicamp - Artigos e Outros Documentos

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