Simple Evaluation of the Paramagnetic Part of the Proton Magnetic Shielding Constant

Abstract

General arguments are proposed to show that the second‐order paramagnetic susceptibility of a molecule is a minimum when the origin of the magnetic vector potential is chosen at the electronic centroid. It is shown that with this choice of gauge, it is possible to evaluate a major portion of the paramagnetic part of the proton magnetic‐shielding constant from a knowledge of the dipole moment, bond distances, and bond angles of the molecule alone. This formulation is applied to the molecules H₂, HF, HCl, HBr, HI, LiH, HCN, C₂H₂, CH₄, and NH₃. Good agreement is obtained when the results are compared with available data from molecular‐beam experiments.