Study of electron densities of methyl acetate, N-methylacetamide and N,N′-dimethylurea by quantum mechanical investigations. Part 1. Gas phase

Abstract

The electron densities of a simple ester, amide and urea derivative have been studied with quantum mechanical methods at the Becke3LYP/6-31 + G* level. Solvent effects were modelled with an SCRF approach based on the SCI-PCM electrostatic continuum solvation model and with explicit inclusion of water molecules at different hydrogen bond donor–acceptor sites of the solutes. Discussions of electron densities use Natural Atomic (NAO) and Natural Bond Orbitals (NBO). Electrostatic interactions with a polar solvent yield polarization of the πCO bond towards oxygen, a higher delocalization of lone pairs from –O– or –NH– into the π*CO anti-bond and a higher localization of lone-pairs at the carbonyl oxygen. Particular different changes in charge densities after explicit hydration of the molecules are discussed.