Radical Reactions in the Decomposition of Energetic Materials

Abstract

Abstract : Our experiments elucidated the decomposition mechanism of energetic materials with geminal dinitro groups using 2-bromo-2-nitropropane as a photolytic precursor for two key intermediates. We used crossed laser-molecular beam scattering experiments and velocity map imaging experiments to determine the primary photodissociation channels and examine the unimolecular dissociation of the highly energized intermediates produced. Our experiments identified a novel mechanism for NO loss from nitroalkyl radicals that circumvents the traditional higher-energy nitro-nitrite isomerization. We computationally characterized the intrinsic reaction coordinate for this NO loss mechanism at the B3LYP/6-311++g(3df,2p) level of theory and calculated the transition-state energies using the G4 composite method. The subsequent dynamics en route to the highly exothermic NO + acetone product channel proceeds through a three-membered ring intermediate. The crossed laser-molecular beam scattering experiments on the 2-nitro-2-propyl radical confirmed the importance of this new mechanism in determining the product branching.