Relative sensitivity coefficients definition

In these equations, k or k2 refer to the rate or equilibrium constant for the unsubstituted molecule, p characterizes the sensitivity of the reaction to electronic substituent effects, and a is the relative electronic effect of the substituent. A substituent at the meta position has a different a value than that of the same substituent at the para position. By definition, p = 1.0 for the pi a of substituted benzoic acids and a is the substituent effect on this reaction. As an example, Figure 3.1 shows the relationship between Hammett a and the log of the acid dissociation constant (log Kf of metu-substituted phenols. The correlation coefficient of this relationship is 0.97. The data is presented in Table 3.1. 

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