Thermal Decomposition of 1-[2,2-bis(Methoxy-NNO-azoxy)ethyl]-3-nitropyrazole

The thermal decomposition of 1-[2,2-bis(methoxy-NNO-azoxy)ethyl]-3-nitropyrazole (I) in isothermal and nonisothermal conditions is studied using the methods of thermal analysis, manometry, IR spectroscopy, mass spectrometry, and NMR H-1. The heat of the alpha -> beta polymorphic transition, the melting heat of beta-I, and the heat of thermal decomposition I are 0.4, 6.2, and 79.2 kcal/mol (274 cal/g), respectively. The composition of the reaction products is analyzed. Among the products formed, N2O, H2O, NO2, NO, N-2, CH3OH, and 3-nitropyrazole are identified. The kinetics of the thermal decomposition of I is complex and cannot be described by simple equations. The effective activation energies of the reaction are determined to be close to 34-35 kcal/mol and slightly increase with the progress of decomposition. It is concluded that the first stage of the reaction involves the elimination of the methoxydiazene oxide group through a five-membered cyclic transition state. The number of nitro groups attached to the pyrazole ring does not affect the kinetics of the thermal decomposition.