Exploring hydration patterns of aldehydes and amides: ab initio investigations

Abstract

Results of an extensive ab initio level investigation of the hydration patterns and energetics of some carbonyl compounds, viz., formaldehyde, acetaldehyde, formamide, and acetamide, are reported. This study employs restricted Hartree-Fock and density functional theory with the 6-31G(d,p) and 6-31++G(d,p) basis sets for exploring explicit hydration of these substrates with 8, 12, and 16 water molecules. Hydrated structures are seen to be dominated by four- and five-membered rings of water molecules as also exhibited by the (H₂O)_n clusters. Electrostatic guidelines are found to be useful for predicting the growth of the smaller hydrated clusters. Hydration of these molecules leads to the weakening of C=O and N-H bonds as revealed by the corresponding internuclear distances and vibrational frequencies.