Delving into Autocatalytic Liquid-State Thermal Decomposition of Novel Energetic 1,3,5-Triazines with Azido, Trinitroethyl, and Nitramino Groups.

Thermal decomposition of 1,3,5-triazines with azido, trinitroethyl, and nitramino groups, the three important energetic functionalities, has been studied with a range of thermal analysis tools. The involved compounds melt under heating with the following mass loss and heat and gas release in the course of thermal decomposition. Model-fitting kinetic analysis resulted in formal reaction schemes with two general stages. In case of the least energetic 6-azido-2,4-bis(2,2,2-trinitroethylamino)-1,3,5-triazine, the first reaction is a first-order reaction followed by a third-order reaction. Alternatively, for 6-azido-2,4-bis(2,2,2-trinitroethylnitramino)-1,3,5-triazine and 2,4,6-tris(2,2,2-trinitroethylnitramino)-1,3,5-triazine, the first step comprises the autocatalytic reaction. The activation energy for the first decomposition step drops from 141 to 122 kJ mol-1 due to the inductive influence of a β-nitramino group. The second general reaction for all species obeys the third-order reaction model with activation energies in the range 112-126 kJ mol-1. On the basis of the analysis of the kinetic data and temporal behavior of the evolved gases, a similar primary decomposition channel, the homolytic cleavage of a C-NO2 bond, has been proposed for all investigated substances.