Thermal features, thermochemistry and kinetics of the thermal dissociation of hexachlorostannates of aromatic mono-amines

Abstract

Thermal properties of hexachlorostannates of several aromatic mono-amines have been examined by thermoanalytical methods (TG, DTG and DTA). Most of the compounds studied undergo complete volatilization upon heating, accompanied by a release of amines, HCl and SnCl 4 to the gaseous phase. The thermal dissociation of these derivatives is realized in essentially one step, in which up to 84% of the sample volatilizes. This is followed by a slow step, seen as a ‘tail’ in TG curves, in which the remaining part of the sample disappears. For some of the compounds, this simple thermal dissociation pattern is disturbed by the occurrence of side processes leading, among other outcomes, to the carbonization of organic fragments of molecules. The thermodynamics and kinetics of the thermal dissociation process were studied using non-isothermal TG curves. Enthalpies of volatilization were evaluated using the van't Hoff equation. The enthalpies of formation and crystal lattice energies of crystalline hexachloro- stannates were then evaluated using the derived values of the enthalpies of volatilization and taking other thermochemical characteristics from the literature. The crystal lattice energy problems were also examined within the framework of the Kapustinskii-Yatsimirskii for- mula. The kinetics of the thermal processes were also considered according to the Arrhenius approach. The Jacobs and Russell-Jones theory is invoked to explain qualitatively the diminution of the rate of volatilization at the end of the process.