Steric effect of o‐methyl groups on the ionization constants of phenols. The influence of the solvent

Abstract By applying McDaniel and Brown's method2 for the separation of polar and steric effects of o‐alkyl groups to Rochester's data1 for the ionization constants of methylphenols in methanol, the o‐effect of a methyl group was shown to be 0.33 ± 0.01 pK‐units. This figure is much larger than the corresponding figure for the o‐effect in water as the solvent (0.14 ± 0.01), showing that the o‐effect is strongly solvent‐dependent and thus lending further support to the view that it is mainly caused by steric hindrance of solvation.