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|Type:||Artigo de periódico|
|Title:||Conformational And Electronic Interaction Studies Of P-substituted α-phenoxyacetones|
|Abstract:||The νCO analysis of p-substituted α-phenoxy-acetones X-φ-O-CH2-C(O)-Me (1-6) indicates the existence of the cis/gauche rotational isomerism. The nearly constant increase in the cis/gauche population ratios for the whole series, on going from carbon tetrachloride to acetonitrile, and the small sensitivity of the carbonyl frequency shifts (ΔνC) for the cis rotamer, on going from electron-attracting to electron-donating substituents, are interpreted as an interplay of the Field (F) and the Inductive (-I) Effects, which originates an almost constant carbonyl bond order, and suggests that the cis rotamers have almost the same energy in the whole series. The decrease in the cis/gauche population ratios, in all solvents, and the deshielding effects on the carbonyl carbon atom, and on the methylene carbon atom in a weaker extent, observed in the 13C NMR spectra, on going from electron-attracting to electron-donating substituents, are discussed in terms of π*CO/nO orbital and Arδ+-Oδ- - Cδ+ =Oδ- Coulombic interactions, which stabilize the gauche rotamers of the investigated compounds. Copyright © 1999 by Marcel Dekker, Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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