Critical role of RO radicals in autocatalytic decomposition of nitrate esters

GD Luo and SY Niu and MQ Wu and XQ Wu and WG Qu and HJ Jiang and IY Zhang and F Zhang, CHEMICAL ENGINEERING JOURNAL, 524, 169477 (2025).

DOI: 10.1016/j.cej.2025.169477

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 under-appreciated role of RO radicals. Such insights may inform the rational design of more effective stabilizers for nitrate ester-based energetic materials.

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