Reaction Mechanism of 1,3,5-Trinitro-s-triazine (RDX) Deciphered by Density Functional Theory

1,3,5-Trinitro-s-triazine, or cyclotrimethylene trinitramine, or RDX, is a sensitive, secondary explosive, which has been the subject of a number of studies regarding the sensitivity and mechanism of decomposition in energetic materials. Several initial mechanistic steps have been proposed for RDX decomposition, with no conclusive agreement upon any one as the definitive pathway. Our research utilizes density functional theory (DFT)-based calculations and concepts, particularly the nuclear Fukui function, to analyze the effects of additive/depletive electronic perturbation upon vapor conformers and crystal RDX structures. Since the nuclear Fukui function is a measure of the physical stress that a nucleus encounters upon a change in the electron population, it may provide useful information regarding the role of each atom in unimolecular decomposition. The results illustrate that both homolytic cleavage of N-N bonds and elimination of HONO from RDX exhibit favorability as initial steps in the decomposition of RDX in either phase. The nuclear Fukui function proved a valuable tool for gaining insight into the initial steps of unimolecular reactions.