SUBSTITUENT EFFECTS IN AROMATIC PROTON NMR SPECTRA .V. BENZENE-INDUCED SOLVENT SHIFTS IN MONOSUBSTITUTED (POLY)METHYLBENZENES

Benzene-induced solvent shifts Δ(=δcyclohexane-δbenzene in proton NMR spectra of 1-substituted-4-methyl-(II), -3,5-dimethyl-(III), -2,4-dimethyl-(IV), -2,6-dimethyl-(V) and -2.4,6-trimethylbenzenes (VI) have been determined. The variation of Δ values with the number and position of Me groups present was explained by assuming a 1:1 solvent-solute complex with the geometry proposed by Williams et al. In forming such a complex, it was shown that the steric effect is most important for protons remote from the substituent while both polar and steric- effects are equally important for protons close to the substituent. © 1969.