THE PMO METHOD FOR ANALYSIS OF STRUCTURAL FEATURES OF POLYCYCLIC AROMATIC-HYDROCARBONS RELEVANT TO ASPHALTENES

Use of the simple perturbation molecular orbital (PMO) method allows t he first-order estimation of energies of formation (E(f)) of polycycli c aromatic hydrocarbons (PAH) as well as their localization (E(L)) and bislocalization (E(b)) energies. These calculations give theoretical support to experimental evidence in the literature which suggests that massive systems (more than six condensed aromatic rings) are not like ly to be found in significant quantities in petroleum samples. From E( L) and E(f) it is predicted that ortho- and perifused systems such as pyrene are more likely than ortho-fused systems such as chrysene. The PMO method is also used for the estimation of first-order interaction energies responsible for the stabilization of free radicals. Copyright (C) 1996 Elsevier Science Ltd.