In the previous paragraph we proposed to try Eq. (3), or just its polar part, as a basis of nonlinear empirical schemes of reactivity. This approach is intended for calculation or prediction of rate constants (or activation barriers) in cases when the differences in the structure of reagents are too great to use linear correlation schemes of the Hammett type. Let us try to build a scheme of reactivity of vinyl monomers in radical addition reactions. Firstly, we can use only the form of Eq. (3), its parameters being the variables for the optimization procedure. On the other hand, we can try to use theoretically obtained parameters of vinyl monomers as indices of reactivity and correlate experimental data with them.

Both variants were studied. Let's start from entirely empirical method, the first approach. For this purpose we are going to use a slightly simplified form of Eq. (3) (supposing only N, effective electronegativity, influences the value of CT energy¹⁾ ):

(eq.4)
где L_i и x_i параметры радикала, а M_j и x_j – мономера (x есть электроотрицательность реагента; L и M включают в себя энтропию, неполярные эффекты и т.д.).