Thermal Decomposition of 1-[2,2-Bis(Methoxy-NNO-Azoxy)Ethyl]-Pyrazole.

The kinetics of thermal decomposition of 1-(2,2-bis(methoxy-NNO-azoxy)ethyl)pyrazole (I) is studied in the isothermal and nonisothermal modes and a conclusion is made about the possible mechanism of this reaction. The heats of melting and thermal decomposition of I are found to be –153.4 J/g (‒9.0 kcal/mol) and 494.3 J/g (28.8 kcal/mol), respectively. Thermal decomposition of I in open and closed reaction systems proceeds in different ways. In an open system, the rate of the process decreases monotonically in accordance with the kinetic law of the order of 0.5. In a closed system, the reaction proceeds with self-acceleration and is described by the autocatalysis equation with the second kinetic order on the autocatalyst. A decomposition mechanism is proposed, according to which the first stage of the reaction proceeds through a cyclic five-membered transition state. In addition, the reaction is susceptible to autocatalysis, mainly by volatile products, among which pyrazole seems to play the most important role. The autocatalysis is of a basic nature. [ABSTRACT FROM AUTHOR]