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Type: Artigo de periódico
Title: A Conformational Analysis Of Some α-aryloxy P-substituted-acetophenones: Solvent Effects On The Vco Infrared Bands
Author: Guerrero S.A.
Olivato P.R.
Rittnerb R.
Abstract: The vco analysis of the α-(p-substituted-phenoxy)p′-substituted-acetophenones [X-Ph-C(O)-CH2-OPh-Y; X=NO2, Y=OMe (1); X= NO 2″, H (2); X=NO2, Y= NO2 (3); X=H, Y=OMe (4); X= H, Y=H (5); X= H, NO2 (6); X=OMe, Y= OMe (7); X=OMe, H (8); X=OMe, NO2 (9)] indicates the existence of cis (I)gauche (II) rotational isomerism. For compounds 12, an additional gauche rotamer (II′) is detected in carbon tetrachloride solution. The almost constant positive carbonyl wavenumber shifts for the cis rotamers of 3-9 are interpreted as due to electronic effects (F, -Iσ and M), whose summing up gives rise to a similar carbonyl bond order. This suggests that the cis rotamer has a similar energy in the whole series. The decrease in the cis/gauche population ratio on going from electron attracting to electron donating substituents within the series 4-6 and 7-9, along with a larger population of the gauche rotamer for 1-3, is discussed in terms of π*CO(LUMO)/n O(OPh-Y) orbital interaction, which stabilises the gauche rotamer for 1-9. Further support for this interpretation is given by the progressive negative carbonyl wavenumber shifts for the gauche rotamers within the series 4-6 and 7-9 on going from electron attracting to electron donating substituents at the phenoxy group, along with the largest negative carbonyl wavenumber gauche shifts for the nitrophenacyl derivatives 1-2.
Rights: fechado
Identifier DOI: 
Date Issue: 2003
Appears in Collections:Unicamp - Artigos e Outros Documentos

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