Standard molar enthalpies of formation and thermal stabilities of artemisinin and its two derivatives: Artemether and artesunate

The constant-volume energy of combustion of crystalline artemisinin and its two derivatives, artemether and artesunate, in oxygen at T = 298.15 K was determined to be {-(7546.53 +/- 3.24), -(7582.28 +/- 3.09), and -(8150.75 +/- 4.24)} kJ.mol(-1) using combustion calorimetry, respectively. The derived standard molar enthalpies of formation of the three compounds in crystalline states at T = 298.15 K were {-(1492.81 +/- 7.62), -(2419.75 +/- 7.52), and -(3320.12 +/- 9.90)} kJ.mol(-1), respectively. The thermal stabilities of the three compounds were also investigated by thermal analysis combined with an FT-IR method.