Abstract
A new method based on Density Functional Theory has been developed for evaluation of electron affinity (EA) of an atom in a molecule. The trend of reactivity of an atom in a molecule obtained by the values of EA and the trend obtained from the values of electron density and Fukui function are in full agreement. The values of EA derived by this new method have also been used to evaluate softness values through Klopman equation. The softness values E-m(double dagger) of nucleophile and E-n(double dagger) of electrophile, and the DeltaE(nm)(double dagger) = \ E-n(double dagger) - E-m(double dagger)\ values derived by them, have been able to explain relative stability of bond, and also the ortho, para and meta directing nature of substituents. Other parameters required for derivation of softness values have been obtained from AM1 and PM3 calculation by using WINMOPAC 7.21 software.