Intramolecular screening effects on n.m.r. chemical shifts. Part I. The anisotropy in the magnetic susceptibility of the C–C and C–H bonds

Abstract

The intramolecular screening contributions to proton resonance shifts arising from the anistropy in the magnetic susceptibility of the C–C and C–H bonds are investigated. The values +4·39 × 10^–6 cm.³ mole^–1 and approximately zero, apparently representing Δ_χ^CC and Δ_χ^CH, are obtained from proton resonance measurements and compared with magnetic birefringence data. It is concluded that the values obtained from n.m.r. chemical shifts are incompatible with those obtained from Cotton–Mouton constants, but can be used to predict proton shifts for a range of saturated hydrocarbons.