7.1 Molecular Dynamics: Radical Reactions in the Decomposition of Geminal Di-Nitro Energetic Materials

Major Goals Radical intermediates are key players in chemical reaction mechanisms in synthetic chemistry, atmospheric chemistry, biological chemistry, and combustion. This work develops new methodology to detect and quantify radical intermediates, and to probe the elementary unimolecular reactions they undergo. The work also benchmarks new state-of-the-art electronic structure methods on open-shell systems. Work beginning in the 1980s Y. T. Lee, IRMPD of RDX has sought to resolve the chemical mechanism of the decomposition of energetic materials. The new methods introduced in our work to probe the key radical intermediates along the energy release pathways should substantially contribute to the development of new energetic materials. Accomplishments The most important accomplishment was our Identification of the radical intermediates that lead to energy release in FOX-7. Indeed this work represent a paradigm shift in the study of the elementary decomposition mechanisms of energetic materials. Prior to this experiment focused on the primary first one or two steps in the decomposition mechanism because the subsequent steps were extraordinarily difficult to characterize. Following our earlier experimental work on di-nitro energetic materials, we sought to computationally investigate the full decomposition pathways of FOX-7 to identify the portion of the decomposition mechanism that resulted in energy release the primary steps typically require energy, they do not release energy. Our published work identifies the energy release mechanism for NO loss involving 3-member cyclic intermediates, rather than anitro-nitrite isomerization, in particular the 1-amino-1-imino-2-nitro-2-ethyl and the 1,1-diamino,2-nitroethen-2-yl radical intermediates The first of the two major experimental results was our crossed laser-molecular beam scattering study of the primary photodissociation channels of chloroacetaldehyde CH2ClCHO at 157 nm.