Theoretical studies of aromatic substitution. Part I. Pyrrole and its protonated species

Abstract

The MINDO/2 method has been applied to pyrrole and its α-, β-, and N-protonated forms. The geometries of the various species have been varied so that the energy of each may approach a minimum. It is found that there are substantial geometrical changes on protonation, and that these changes differ for the different cations. The sequence of reactivity is found to be α < β < N, in accordance with experimental findings. The calculations on pyrrole are compared with the results of other all valence electron calculations.