Thermal properties, thermochemistry and kinetics of the thermal dissociation of hydrochlorides of some mononitrogen aromatic bases

Abstract

Thermal properties of the hydrochlorides of several nitrogen aromatic bases have been elucidated via thermoanalytical investigations. All the compounds studied undergo decomposition upon heating, leading to their total volatilization. The dissociation process proceeds in two stages having different kinetics. The existence of these stages is explained on the basis of the Jacobs and Russell-Jones model of the kinetics of dissociative sublimation processes. The enthalpies of thermal dissociation of the salts have been evaluated from the non-isothermal thermogravimetric curves, and these values, together with thermochemical data available in the literature, have been used to evaluate the enthalpies of formation and the crystal lattice energies of the compounds. The ‘thermochemical’ radii for appropriate cations have been determined from the Kapustinskii–Yatsimirskii equation. The influence of the structure of the nitrogen bases on the thermal behaviour of their hydrochlorides is also discussed.