Weak molecular interactions—I : Solvent effects on the proton magnetic resonance spectra of t-butyl and adamanthyl halides

Abstract

The effect of aromatic solvents upon the PMR spectra of t-butyl and l-adamanthyl halides has been studied in an attempt to discover the mechanism by which the changes in chemical shift are produced. If the formation of 1:1-complexes in these solutions is assumed, the temperature dependence of the chemical shifts can be used to derive thermodynamic parameters. These parameters do not seem to respond significantly to changes in the structure of the solute or solvent. In addition freezing point diagrams give no evidence of compound formation. To explain the geometrically specific shifts which are nonetheless observed, it is suggested that the solute dipole causes a weak ordering of the solvent, which is geometrically, but not thermodynamically, equivalent to a complex.