Sublimation/volatilisation kinetics of 8-hydroxyquinolines and their nitro-derivatives

5-Nitro-8-hydroxyquinoline (B) and 5,7-dinitro-8-hydroxyquinoline (C) were obtained from nitration of 8-hydroxyquinoline (A) and purified in acetone m edium 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=76 degreesC (A) and 180 degreesC (B)) in d ifferent proportions as a function of the heating rate, characterising the sublimation and the volatilisation processes, respectively. The thermal sta bility of the compounds follow the order: A (77 degreesC)<B (121 degreesC)< C (222 degreesC). Kinetic parameters through TG curves, dynamic process, us ing heating rates of 1, 2.5, 5, 10 and 20 degreesC min(-1), enabled to obta in the following increasing order to the activation energy values of the co mpounds: 80.4 (A), 102.0 (B) and 153.9 kJ mol(-1) (C). Other kinetic parame ters as pre-exponential and half-lifetime were also estimated.