Electric reaction field of a molecular octopole and the solvent proton chemical shift of methane

Abstract

The known gas-to-infinite-dilution ¹H n.m.r. chemical shift of methane possessing a molecular octopole is usually attributed to the van der Waals term, σ_W. Recently, Homer and Percival showed that the so-called buffeting interaction term, σ_BI, also makes a contribution to the solvent shift of methane. In this work another contribution to the solvent shift, due to the reaction field of the electric octopole of methane, is considered. A formula for this electric-field contribution to the chemical shift, denoted by σ_E, is presented and compared with experiment.