Standard enthalpies of formation of 2-aminobenzothiazoles in the crystalline phase by rotating-bomb combustion calorimetry

Abstract

The standard molar enthalpies of combustion of 2-aminobenzothiazole (2AB), 2-amino-4-methyl-benzothiazole (2A4MB), and 2-amino-6-methyl-benzothiazole (2A6MB) were determined in the crystalline phase at T=298.15K using a rotating-bomb combustion calorimeter. The molar energies of combustion of these compounds were found to be: (−4273.6±0.9), (−4896.9±1.1), and (−4906.9±1.2)kJ·mol−1, respectively. From these values, the corresponding standard molar enthalpies of formation in the solid phase were obtained as: (59.55±1.28), (2.71±1.50), and (13.53±1.53)kJ·mol−1, respectively. The enthalpies of formation in the gas phase were determined using the experimental enthalpies of formation in the solid phase and predicted values of the enthalpies of sublimation. Additionally, the enthalpies of formation in the gas phase were calculated by means of the Gausian-4 theory, using several gas-phase working reactions, and were compared with those found using the predicted enthalpies of sublimation.