Artículos de revistas
Conformational and electronic interaction studies of alpha-substituted carbonyl compounds. XIV. alpha-(arylsulfonyl)-p-substituted acetophenones
Registro en:
Phosphorus Sulfur And Silicon And The Related Elements. Gordon Breach Sci Publ Ltd, v. 130, n. 155, n. 174, 1997.
0308-664X
WOS:000076137500016
10.1080/10426509708033706
Autor
Olivato, PR
Guerrero, SA
Institución
Resumen
The nu(CO) IR analysis of alpha-(p-phenylsulfonyl)-p-substituted acetophenones X-0C(O)CH2S(O)(2)0-Y 1-8, being X and Y = NO2, H and OMe substituents, supported by Molecular Mechanics data of the alpha-methylsulfonylacetophenone (model compound), indicates the existence of the cis/gauche rotational isomerism. The less polar gauche, rotamer is the more stable (conc. congruent to 90%) and the more polar ris rotamer is the less stable one along the series, Compounds 4 (X = Y = H) and 3 (X = H, Y = OMe) present another less stable and rather polar gauche, rotamer, The almost constant carbonyl gauche, shifts (Delta nu(g2)) together with the quasi-invariability of the cis/gauche ratios, when X varies and Y is fixed, indicates a very nearly constant summing up of pi*(CO)/sigma(C . SO2) and pi(CO)/sigma*(C . SO2) orbital interactions. The progressive stabilization of the gauche(2) rotamer when X is fixed and Y changes from NO, to OMe substituents, along with the parallel decrease of the positive sulfonyl asymmetric frequency shifts (Delta nu(SO2(as))) is discussed in terms of the progressive contribution of the O-(SO2) --> C-(CO) electrostatic and charge transfer interactions. Additional support for the proposed interactions is given by the large NAE mean value for the alpha-methplene carbon chemical shifts together with the upfield shift of the beta-ketosulfones mean carbonyl carbon chemical shifts in relation to that of the beta-ketosulfoxides. 130 155 174