ABSTRACT
Taft parameters are constants that describe the steric effect of a substituent over the molecule’s reactivity. They describe the way a particular substituent in a molecule will influence the molecule’s reactions through polar (inductive, field, and resonance) and proper steric effects. The initial Hammett equation in organic chemistry describes a linear free-energy relationship between the reaction rates and equilibrium constants for many reactions that are involving benzoic acid analogs, with meta- and para-substituents to each other, with just two parameters: a substituent constant and a reaction constant. Hammett’s idea was that for any two reactions with two benzoic acid derivatives only differing in the substituent’s type, the change in the free energy of activation is proportional to the change in Gibbs free energy. Taft equations are used in pharmaceutical industry/chemistry for QSAR studies of molecules with biological activity and for drug design.
