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|Type:||Artigo de periódico|
|Title:||Conformational analysis of fluoroacetoxime and of its O-methyl ether by H-1, C-13 and N-15 NMR and theoretical calculations|
|Abstract:||The solvent dependence of the H-1, C-13 and N-15 NMR spectra of (E)-fluoroacetoxime [(E)-FAO] and of (E)-fluoroacetoxime O-methyl ether [(E)-FAOME], was examined and the HF, CF and NF couplings are reported. Density functional theory (DFT) at the B3LYP/6-311++g(2df,2p) level with ZPE (zero point energy) correction was used to obtain the rotamer geometries. In both (E)-FAO and (E)-FAOME the DFT method gave two energy minima corresponding to the cis (F-C-C = N, 0degrees) and gauche (F-C-C = N, 124.1degrees) rotamers. In contrast, in (Z)-FAO the DFT method gave only one energy minimum corrsponding to the trans rotamer. The (4)J(HF) and (1)J(CF) couplings in (E)-FAO were analyzed by solvation theory assuming the cis and gauche forms to give E-cis - E-gauche = 3.3 kcal mol(-1) in the vapor phase, decreasing to 1.54 kcal mol(-1) in CCl4 and -1.19 kcal mol(-1) in DMSO (1 kcal = 4.184 kJ. In (E)-FAOME the observed couplings, when analysed similarly by solvation theory, gave E-cis - E-gauche = 2.2 kcal mol(-1) in the vapor phase, 0.91 kcal mol(-1) in CCl4 and -1.18 kcal mol(-1) in DMSO. The (3)J(NF) coupling was independent of the molecular conformation, as it did not change with the solvent polarity. Copyright (C) 2003 John Wiley Sons, Ltd.|
|Editor:||John Wiley & Sons Ltd|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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