Estimation of intramolecular cyclization activation energies via isothermal gravimetric analysis: A technical note

Isothermal gravimetric analysis was used to monitor the weight loss of 4 exploratory compounds as an indicator of their solid-state thermal stability. Data obtained from TGA were further processed via a model-free isoconversional method to estimate the activation energy values. These values ranged from 140 to 218 kJ/mol and were inversely related to their corresponding surface areas. Based on their activation energy values, the relative stability of these 4 exploratory compounds can be ranked as C>D>B>A and their formulation development activities can be prioritized.