9-azidoacridine reacts under 1,3-dipolar reaction with alkyne derivatives to yield 9-(4- and 5-substitu ted-1,2,3-triazol-1-yl)acridine derivatives. The extrusion of N-2 from these compounds leads to formation of carbene and biradical intermediates. Radical moieties interact with the acridine ring to form 1Hpyrido-14,3,2-4 derivatives. The focus of this study was on the theoretical and computational studies of the pathways of the products. The energy levels of the reactant species, TS forms (transition states), products, the free energies of reaction (Delta(r)G and Delta G(#)), HOMO & LUMO orbital levels, the Delta EHOMO-LUMO, dipolmoments, rate constants by using Eyring's equation (k and k'), structural data were calculated by OFT (B3LYP/6-31G*) method. The relative energies (in kcal mol(-1)) of the transition states as well as the biradical (singlet (S) and triplet (T); and carbene (singlet (S) and triplet (T); intermediates of the pyrolysis reactions on the reactants were investigated as well. The stepwise of the N-2 elimination reactions have also investigated. The values of the free activation energy (Delta G(#)) in the concerted N-2 elimination pyrolysis reactions were correlated to the decomposition temperature (T-Decom) of reactants. (C) 2017 Elsevier B.V. All rights reserved.