0000000000671313
AUTHOR
F.h. Ferretti
Conformational equilibrium and intramolecular hydrogen bond of 4′X and 4X substituted 2′(OH)chalcones
Abstract By using the AM1 method on 4X and 4′X substituted 2′(OH)chalcones (X=H, OH, F, Cl, CH 3 , CH 3 O, N(CH 3 ) 2 , and NO 2 ), certain currently unclear structural characteristics, conformational equilibria, intramolecular hydrogen bonds and UV spectroscopic properties had been clarified. The compounds studied have non-planar structures. The 2′(OH),4′Xchalcones only present the trans - s - cis conformation. trans - s - cis and trans - s - trans conformers of 2′(OH),4X-chalcones have a comparable thermodynamic stability. For these chalcones, a conformational equilibrium at 298 K exists, with 91% of the trans - s - cis form. The proposal of analyzing the intramolecular hydrogen bond of 2…
A theoretical and experimental study of the formation mechanism of 4-X-chalcones by the Claisen–Schmidt reaction
Abstract A theoretical and experimental study on the formation of 4-X-chalcones (X=H, Cl, F, OCH3, N(CH3)2) was carried out by the Claisen–Schmidt reaction. The influence of pH and temperature was analyzed. Under the adopted experimental conditions 4-X-chalcones were the only reaction products. In the theoretical study, the thermodynamic magnitudes and the reactivity indexes calculated with the AM1 method were used. The mechanism of Nayak and Rout was analyzed critically and a new mechanism was proposed, characterized by: (1) rapid nucleophilic attack of the catalyst (OH−) on the carbon atom of the methyl group of acetophenone; (2) attacks of the acetophenonate ion on the carbon atom of the…