A DSC study of new compounds based on (E)-3-(azulen-1-yldiazenyl)-1,2,5-oxadiazole

Abstract

Exothermal decomposition of six (E)-(substituted azulen-1-yldiazenyl-1,2,5-oxadiazoles) was investigated by differential scanning calorimetry (DSC) under non-isothermal conditions, in inert atmosphere. From the DSC curves recorded either at various heating rates for three compounds, or at 10 K min−1 for the rest, several physical properties such as the melting temperature, melting heat, temperature and heat of decomposition were evaluated. The activation parameters of the decomposition processes were determined by analyzing their multiple curves, measured at different heating rates, using both the Friedman and Flynn–Wall–Ozawa isoconversional methods and model-fitting methods. The linear dependence of the activation energy on conversion supports the idea of the single-step nature of the decomposition processes for all examined compounds. The decomposition steps were identified from the experimental DSC curves, and their kinetic parameters were evaluated using linear regression methods. New insight into the relationship between melting and structural properties was gained if the equilibrium free energy of melting was splitted into its energetic and entropic components. The resulted thermodynamic and kinetic parameters are used to predict the hazards associated with these compounds.