First principle study of the structure of conjugated amides and thioamides

On the basis of ab initio and density functional theory (DFT) calculations of the o-coumaric amide and thioamide, the latter is found to have better delocalization. It is demonstrated that the thioamide function features stronger attraction for electron density from the conjugated residue. Therefore, the electronic distribution in the thioamide favors stable phenoxyl radical formation. This is a reason to expect better antioxidant activity of the thioamide. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007