Thermodynamic study on six tricyclic nitrogen heterocyclic compounds by thermal analysis and effusion techniques

Abstract

The molar sublimation and vaporization enthalpies of acridine, phenanthridine, 1,7-phenanthroline, 1,10-phenanthroline, 4,7-phenanthroline and phenazine were determined at the averages of their respective experimental temperature ranges (ΔcrgH0m (<T>) and ΔlgH0m (<T>), respectively) from the temperature dependencies of vapor pressure determined using Knudsen Effusion Mass Loss (KEML), Torsion Effusion (TE) and Isothermal Thermogravimetry (ITG) above their solid and liquid phases. The fusion characteristics (melting temperatures and the molar standard enthalpies of fusion at their melting temperatures) measured by Differential Scanning Calorimetry (DSC) were compared with the available literature values. Solid and liquid vapor pressure data determined by KEML, TE and ITG techniques as well as ΔcrgH0m (<T>) and ΔlgH0m (<T>) values, adjusted at 298.15K by using the values of Cp(cr) and Cp(l) calculated by a well-known group additivity method, were found to be fairly correlated and are consistent with the available literature data. Final ΔcrgH0m(298.15K) values were also provided as weighted averages of all the available data.