On the anomalous decomposition and reactivity of ammonium and potassium dinitramide

Mechanistic pathways for the thermal decomposition of the solid-state energetic oxidizers ammonium dinitramide (ADN) and potassium dinitramide (KDN) have been deciphered by carefully considering previously performed experimental studies and using state of the art quantum chemical modeling of molecular clusters. Decomposition is governed by surface chemical processes, involving polarized (twisted) dinitramide anions of reduced stability. Under atmospheric and low-pressure conditions, the rate-determining step for the decomposition of these dinitramide salts is the dissociation into NO(2) and NNO(2)(-) radicals. The activation barriers for these steps are estimated to be 30 and 36 kcal/mol for ADN and KDN, respectively. The known stabilizing effect of water is explained by its hydrogen bonding ability, which counteracts polarization of surface dinitramides. The reactivity of ADN toward various chemical environments is likely explained through metastable decomposition radical intermediates. Donation of hydrogen bonds, antioxidant character, and basicity are properties believed to correlate with a compound's ability to act as a stabilizer for dinitramide salts.