Medium Effects in Nuclear Magnetic Resonance. IV. A Refined Theory for Nonpolar Gases

Abstract

Following the general theory for medium NMR shifts in gases as outlined in Part I of this series, two improvements are proposed. For the calculation of the van der Waals interaction a repulsive term has been added to the customary attractive term. Wherever intermolecular distances are required, a properly averaged distance between the site of the measured proton in the solute molecule and the center of the solvent molecule is used rather than the distance between the centers of the molecules. The implications of these corrections for nonpolar molecules are discussed, and new values for the bond parameters B are proposed.