Conformational and electronic interaction studies of some classes of mono- and di-substituted carbonyl compounds at the alpha position

Abstract

The main purpose of this project is to study the various types of interactions which govern the stability of a particular molecular conformation and, consequently, are responsible for the observed macroscopic properties of the substance. In order to achieve these objectives, the conformational equilibria of selected model compounds will be studied along with the most important effects which determines the stability of a given conformation i.e. anomeric, hyperconjugative and gauche and intramolecular hydrogen bonds. This study will be focused on the following beta-thiosubstituted-carbonyl compounds: (a) 5-substituted- 2-(ethylthioacetyl)-, 2-(ethysulfinylacetyl)- and 2-(ethylsulfonylacetyl)-furans and -thiophenes; (b) para-substituted alpha- phenylsulfinyl- and alpha-phenylsuflonyl-N-methyl-delta-valeroctams; (c) para-substituted (alpha-phenylseleno-alpha-ethylsulfinyl)-acetophenones and (d) 4'-substituted 2-(ethylsulfonyl) phenylacetates. The conformational analysis will be performed according to the methodology previously developed in our laboratories, involving experimental measurements by infrared spectroscopy in conjunction with theoretical calculations of the geometries and energies of the conformers in the gas and in the solution phase as well. Studies on the orbital interactions which stabilize the main conformations will be performed through the NBO method (Natural Bond Orbital). (AU)