Unimolecular Decomposition of Methoxysulfonyl Azide: Insights From Direct Dynamics Simulations and Electronic Structure Calculations

Small inorganic molecules containing sulfur, nitrogen, and oxygen have been extensively studied due to their roles in industrial processes, biological systems, and atmospheric chemistry. is one such molecule, generated via gas‐phase pyrolysis of methoxysulfonyl azide (MSA) [CHOS(O)N]. Previous flash‐vacuum pyrolysis experiments, supported by CCSD(T)/6‐311++G(2df, 2p) electronic structure calculations, indicated that MSA decomposes through two competing pathways involving a methoxysulfonyl nitrene intermediate (CHOS(O)N), ultimately forming , HCHO, and . In the present work, we combine electronic structure theory with Born–Oppenheimer direct classical trajectory simulations to investigate the unimolecular dissociation dynamics of MSA and to elucidate its atomistic reaction mechanisms. Benchmarking against correlated wavefunction methods showed that density functional B3LYP/6‐31G** level of theory is best suited to perform the on‐the‐fly dynamics. Reactant molecules were activated using classical microcanonical sampling and the integrated trajectories were analyzed to characterize product branching, intermediate lifetimes, and mechanistic pathways. The simulations reveal detailed dissociation mechanisms, including Curtius‐type rearrangement and 1,4‐H shift processes, providing molecular‐level insight into the decomposition chemistry of MSA.