Catalytic Behavior of Acids and Bases

One of the characteristics of acids and bases is that they catalyze certain reactions. Many years ago, J. N. Bronsted studied the relationship between acid strength as measured by the dissociation constant and the rate of a reaction that is catalyzed by the acid. The relationship that Bronsted recognized can be written as 

The form of this equation shows that a graph of log k versus p/L, should be linear with a slope of —n and an intercept of log C. Dissociation of the acid produces the anion hr that accepts protons from water, as shown in the equation 

The equilibrium constant, fCa, is related to the free energy change for the dissociation of the acid, AGa, by the equation 

Equation (9.72) is known as a linear free energy relationship, and it shows that there should be a linear relationship between the logarithm of the rate constant for a reaction and the free energy for the dissociation of the acid. 

Relationships can be developed in a similar manner for reactions that are catalyzed by bases. The equation that can be obtained is 

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