Thermal study of chalcones: Thermal decomposition of chalcone and its hydroxylated derivatives

Abstract

Chalcones α-β-unsaturated ketones are found in large plant species. Synthesis of chalcones and its three analogues hydroxy group at 2′, 3′ and 4′ positions (2–4) was carried out. The studies of thermal behavior were made by thermogravimetry (TG) and differential scanning calorimetry, both under oxygen and nitrogen purge gases. In addition, the kinetic evaluation was carried out under heating rates of 5, 10 and 20 °C min−1 with sample mass of 2 mg in open crucibles. The kinetic results obtained by TG analysis showed that the thermal behavior under oxygen shows that the functional hydroxy group substitution affects the thermal behavior of each molecule, with a gradual increase in the thermal decomposition. The activation energy (Ea/kJ mol−1) showed under a nitrogen purge gas that the hydroxy group at 3′ position (3′-hy-chalcone compound) has a different kinetic behavior, while the chalcone under oxygen showed a low activation energy when compared with the other hydroxy groups.