How the Chalcogen Atom Size Dictates the Hydrogen‐Bond Donor Capability of Carboxamides, Thioamides, and Selenoamides

Thioamides and selenoamides are better hydrogen-bond donors than carboxamides because their amino groups more positively charged. Quantum chemical analyses reveal that this counterintuitive phenomenon, which cannot be explained by the electronegativity, originates from larger electronic density flow nitrogen lone pair of NH2 group towards lower-lying π* orbital on C=S or C=Se bond. This difference can traced back to effective steric size chalcogen atoms. More information found in Research Article C. Nieuwland Fonseca Guerra (DOI: 10.1002/chem.202200755).