Critical role of RO radicals in autocatalytic decomposition of nitrate esters

Nitrate esters (R–ONO₂) have long served as essential constituents in solid propellants owing to their excellent energetic performance. However, their intrinsic tendency toward autocatalytic decomposition undermines storage and operational safety. Although NO₂ radicals—formed by initial RO–NO₂ bond cleavage—are acknowledged to drive low-temperature autocatalysis, the exact mechanism is disputed. Here, we integrate molecular dynamics simulations with quantum chemical calculations to elucidate the early decomposition events and key bimolecular reactions that sustain autocatalysis. We select isopropyl nitrate (iPN) and nitroglycerin (NG) as model mono- and polynitrate esters, respectively. The results indicate that, in condensed-phase thermal decomposition of iPN, RO radicals—rather than NO₂-mediated H-abstraction or acid-hydrolysis pathways—exhibit the lowest free energy barriers and greatest exothermicity. For NG, RO radicals preferentially undergo unimolecular dissociation or react with NO₂, thereby propagating radical chain pathways. These findings refine our mechanistic understanding of nitrate ester autocatalysis and highlight the hitherto underappreciated role of RO radicals. Such insights may inform the rational design of more effective stabilizers for nitrate ester-based energetic materials.