Using the isomerization method, Isomerization Stabilization Energies (ISEs) are computed for some five-membered heterocyclic rings, penta-and hepta-fulvene compounds. Using quadratic model (Delta omega(Q)), Janak's approximation (Delta omega(J)) and recently introduced Morse-Like function approach (Delta omega(M)) the relative electrophilicities are evaluated for these systems. An excellent linear correlation between the latter and some aromaticity measures are observed and also the orders of aromaticities are successfully predicted using the Minimum Electrophilicity Principle (MEP). Therefore, it is claimed that for prediction of electrophilicities in different systems, the obtained values from the Morse-Like function are more reliable than those which are calculated from the approximate models. (C) 2009 Elsevier B.V. All rights reserved.