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|Type:||Artigo de periódico|
|Title:||Conformational Analysis Of Fluoroacetoxime And Of Its O-methyl Ether By 1h, 13c And 15n Nmr And Theoretical Calculations|
|Abstract:||The solvent dependence of the 1H, 13C and 15N NMR spectra of (E)-fluoroacetoxime [(E)-FAO] and of (E)-fluoroacetoxime 0-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, 0°) and gauche (F - C - C=N, 124.1°) rotamers. In contrast, in (Z)-FAO the DFT method gave only one energy minimum corrsponding to the trans rotamer. The 4JHF and 1JCF couplings in (E)-FAO were analyzed by solvation theory assuming the cis and gauche forms to give Ecis - Egauche = 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 = 4.184kJ. In (E)-FAOME the observed couplings, when analysed similarly by solvation theory, gave Ecis - Egauche = 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 3JNF coupling was independent of the molecular conformation, as it did not change with the solvent polarity. Copyright © 2003 John Wiley & Sons, Ltd.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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