Thermal Degradation Kinetics and Geometrical Stability of D-Sucrose

摘要

Thermal degradation kinetics of solid-state D-sucrose and D-glucose were studied using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) techniques. The melting and decomposition process of the two sugars were displayed as endothermic peaks on the DTA curve under nonisothermal conditions. It was noticed that the melting peak temperature of D-glucose was lower than that of the other sugar. For the decomposition processes, the opposite occurred. The decomposition kinetic parameters, such as the decomposition activation energy (Ed) and the frequency factor (K_o), were calculated by employing different approximations. The relative stability of the studied sugars was determined. Molecular mechanics (MM) calculations showed that the optimal geometric structure (OMG) of D-sucrose was at least three orders of magnitude more stable than the molecular geometric (MG) structure. These calculations indicate that the potential energy (PE (kcalmol~(-1))) of the OMG is about three (1.142 x 10~3) orders of magnitude lower than the MG structure of the same sugar. So, optimizing the geometry of the molecular structure (OMG) is very important for understanding the stability of this sugar.