Conformational dependence of the molecular charge distribution and its influence on intermolecular interactions

The conformational dependence of the intermolecular electrostatic interaction energy has been studied for three model compounds interacting with water molecules. The variation in the molecular charge distribution with conformation can have an important influence on intermolecular hydrogen-bond energies. Rotational barriers of hydrated molecules are substantially affected when this variation is taken into account. The significance of this effect has been evaluated for N-methylacetamide, ethanol and N,N-dimethylacetamide. It is shown that the conformational dependence of the molecular charge distribution can be described with high accuracy by expressing the atomic multipole moments as a short Fourier series in the dihedral angle.