Abstract:
The reactivity of acetaldehyde and some aromatic aldehydes towards acid-catalysed oxygen-18 exchange reactions with H2O18 was studied using the density functional theory (DFT)-based reactivity descriptors local softness and local hardness. Local softness is used to predict the preferable reactive sites within a given molecule, whereas local hardness reproduces the experimental intermolecular reactivity trends. A new concept, intrinsic global hardness, obtained via filtering out the volume effect of the global softness, shows an excellent correlation with the degree of aromaticity of the compounds.