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  • 1 Instituto de Química — Unesp C.P. 355 CEP 14801-970 Araraquara, SP Brazil C.P. 355 CEP 14801-970 Araraquara, SP Brazil
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Abstract  

5-Nitro-8-hydroxyquinoline (B) and 5,7-dinitro-8-hydroxyquinoline (C) were obtained from nitration of 8-hydroxyquinoline (A) and purified in acetone medium and under heating in which the formation of (B) or (C) depends on the amount of HNO3 added. TG curves present mass loss in only one step before and after the melting point (T m =76C (A) and 180C (B)) in different proportions as a function of the heating rate, characterising the sublimation and the volatilisation processes, respectively. The thermal stability of the compounds follow the order: A (77C)<B (121C)<C (222C). Kinetic parameters through TG curves, dynamic process, using heating rates of 1, 2.5, 5, 10 and 20C minȡ1 , enabled to obtain the following increasing order to the activation energy values of the compounds: 80.4 (A), 102.0 (B) and 153.9 kJ mol−1 (C). Other kinetic parameters as pre-exponential and half-lifetime were also estimated.