Mechanisms of thermolysis of nitro-substituted 1-[2,2-bis(methoxy-NNO-azoxy)ethyl]pyrazoles

Abstract

Mechanisms of thermal decomposition of nitro-substituted 1-[2,2-bis(methoxy-NNO-azoxy)ethyl]pyrazoles were investigated using quantum chemical calculations at the CCSD/aug-cc-pVDZ and CBS-QB3 levels of theory. The main channel of thermolysis of these compounds is the reaction involving transfer of one of the two H_β atoms to the O(1) atom via the five-membered transition state with an activation enthalpy of about 170 kJ mol⁻¹ and affording MeOH and N₂O as the major volatile products. The study of alternative mechanisms of thermal decomposition revealed inefficiency of the channel leading to elimination of nitropyrazole. The results of calculations are in good agreement with the experimental data reported in the literature.