Abstract

The effect of substituents on the relative stabilization energy (E_RS) of phthalane-X carbocations has been studied with PM3 semi-empirical molecular orbital theory. The results show that the amino group gives E_RS less than zero for very big amount and that will increase stability of carbocation by π-electron donation, whereas the nitro group gives height amount of E_RS more than zero and that will lead to difficulties of an intermediate carbocation formation because of its strong σ- and π-accepting nature. E_RS decreases with increase in the phenyl rings attached to cation. When electron withdraws substituents attached, it will destabilize the cation, because they act as π-electron donors.

Key words: Relative stabilization energy (E_RS), PM3 semi-empirical, isodesmic reactions.