A simple method to obtain an approximate solution of the Free-Wilson model.

A method is proposed which yields an approximate solution of the Free-Wilson model very rapidly without using a computer. Although the resulting group contributions are numerically somewhat different from the exact Free-Wilson solution they correctly reflect the relative order of the substituents with respect to their effect on biological activity within each position as well as the relative importance of different positions. Thus, the approximate results can well be used to select the most promising candidates for further synthesis and testing.