Electrostatic bond dipole moments from dimethyl ether, methanol, methane and water

Abstract

Bond dipole moments are derived for the O—H, C—H, and C—O bonds from ab initio calculated and experimentally determined electrostatic multipoles of dimethyl ether, methanol, methane and water, using an electrostatic model with point dipoles placed at the midpoints of the bonds between atoms and directed along the bonds. Multipole moments up to and including L= 6 moments for each of the molecules are used. It has been found that the model leads only to a fair description of the molecular potential. Owing to the large correlation between the carbon–oxygen bond moments and the oxygen–lone pair moments the latter could be omitted from the model without affecting the quality of the fits.

From a molecular-mechanics calculation, with the present electrostatic parameters, on the C_i and D_3d conformation of a crown ether molecule (18-crown-6), there followed a lower energy for the C_i conformation which is in agreement with experiment.