Dependence of nuclear magnetic resonance solvent anisotropy shifts on the size of the solute molecule

Abstract

Swnmary Solvent magnetic anisotropy shifts for nonpolar solutes in benzene show a systematic decrease with increasing size of the solute molecule, in agreement with theoretical predictions based on a geometrical model.THE effects of solvents with magnetically anisotropic molecules (e.g. benzene) on n.m.r. chemical shifts are an aid to structure determination.1-* The resonance positions in the anisotropic solvent are compared with those for the same solute in an isotropic solvent (e.g. carbon tetrachloride), with an internal tetramethylsilane (TMS) reference in both solutions. For non-polar solutes, the collision complex model1 successfully applied to solutes with polar groups is inappropriate, and the shifts depend mainly on the size and shape of the solute molecules.