The effect of the Me2S+ group on the ionization of benzoic acid has been re-examined in comparison with that of the Me3N+ group. The thermodynamic pKa values of o-, m-, p- Me2S+ and o-, m-, p-Me3N+ substituted benzoic acids have been determined in 65 vol% aq. dimethyl sulfoxide, 50 vol% aq. ethanol, and in water potentiometrically. The result of this work, σp-Me2S+⪢ σm-Me2S+ is contrary to that previously found by others, σp-Me2S+< ...
