The Effect of Structure Upon the Reactions of Organic Compounds. Temperature and Solvent Influences

Abstract

The effect of a substituent upon the heat of ionization of an organic acid is far from identical with its effect upon the free energy of ionization. In the case of benzoic acid derivatives the entropy of ionization varies with structure in a way which can be predicted from the temperature dependence of the dielectric constant of the solvent, and which is closely correlated with the effect of a change in the dielectric constant of the solvent upon the relative strengths of substituted and unsubstituted acids. The behavior of aliphatic acids is more complicated, probably because of their less rigid structure. Similar considerations apply to the effect of changes in structure of reactant upon other equilibria and upon reaction rates.