No abstract

The thermal decomposition of ammonium dinitramide (ADN) and potassium dinitramide (KDN) were examined neat and in solution. Isothermal kinetics were measured (160−220 °C) by monitoring dinitramidate loss and were found to be first-order. Ammonium ion loss and gas formation were not good measurements of ADN decomposition since they reflect the fate of the ADN decomposition product ammonium nitrate. Kinetics of decomposition were nearly identical for ADN neat (proteo- and deutero-), ADN in water (1 or 20 wt %), ADN in various pH aqueous buffers, and for aqueous KDN (1 wt % in water or deuterium oxide). The activation energy, calculated for ADN, was about 40 kcal/mol (167 kJ/mol) for neat ADN and 37 kcal/mol (155 kJ/mol) for aqueous solutions of ADN. Decomposition of ADN in aqueous buffers suggested that under the conditions of these studies decomposition of dinitramidate or its parent acid proceeds at about the same rate at pH 3, pH 5, and unbuffered but decreased by about 40% at pH 9. Neat KDN was unique in that it decomposed about an order of magnitude slower than ADN, but its decomposition increased to be comparable to that of ADN when KDN was aqueous or when any ammonium salt was mixed with KDN. Nitrous oxide and nitrate (or nitric acid) were the principal decomposition products of dinitramide. Nitrogen gas was also formed, to a significant extent in the decomposition of ADN and to a small extent in that of KDN. Nitrogen gas resulted from the interaction of ammonium or ammonia with the nitrate or gaseous nitrogen oxides. Studies of 15N-labeled ADN confirm that one N−NO2 bond remains intact, forming nitrous oxide, while the other nitro group combines with the nitrogen from ammonium to form nitrogen gas. Several decomposition pathways consistent with these findings are considered.

The thermal decomposition of 1,3,3-trinitroazetidine (TNAZ) and related 3,3-dinitroazetidium (DNAZ+) salts was examined neat and in solution. TNAZ kinetics were found (160−250 °C) to be first-order and nearly identical neat and in benzene, with an activation energy of 46.6 kcal/mol (195 kJ/mol). The DNAZ+ salts were less thermally stable than TNAZ, and neat did not decompose in a first-order fashion. However, in aqueous solution the DNAZ+ salts did decompose following first-order kinetics; their rates were similar with minor differences apparently related to the strength of the anion as a conjugate base. Like simple nitramines such as dimethylnitramine, TNAZ tended to form N2O rather than N2, but unlike other nitramines it formed about as much NO as N2O. TNAZ isotopomers labeled with 13C and with 15N were prepared and used to identify the origin of the decomposition gases and the identity of the condensed-phase products. Early in the decomposition of TNAZ, most of the NO came from the nitro group attached to the azetidium ring nitrogen. Most of the N2O was the result of the nitro groups interacting with each other, while the majority of the N2 contained one nitrogen from the ring. Many condensed products have been identified, but five stand out because they are formed in the thermolysis of TNAZ and the three DNAZ+ salts [NO3 -, Cl-, N(NO2)2 -]. These are 3,5-dinitropyridine (M, always a minor product), 1-formyl-3,3-dinitroazetidine (L), 1,3-dinitroazetidine (K), 1-nitroso-3,3-dinitroazetidine (E), and 1-nitroso-3-nitroazetidine (G); the identity of the first four has been confirmed by use of authentic samples. Of these five, the last four have been shown to interconvert with TNAZ and each other under the conditions of these experiments. This study confirms the presence of two competitive TNAZ decomposition pathways. Under the conditions of this study, N−NO2 homolysis is slightly favored, but products, such as K, resulting from C−NO2 scission, are also well represented.

The purpose of this study was to evaluate whether a relationship exists between thermal stabilities of selected fuel additives and their effectiveness as diesel fuel cetane improvers. The additives were 2-ethylhexyl nitrate, isopropyl nitrate, tetraethylene glycol dinitrate, di(tert-butyl) peroxide, and methylcyclopentadienyl manganese tricarbonyl. Rate constants and activation parameters were determined for the thermolysis of the neat additives as well as the additives dissolved in various solvents and fuels. In all cases, decomposition kinetics were first-order. Mass spectral analysis was used to identify products from the thermal decomposition of the additives in various solutions. Thermal stability, as measured by the kinetics of decomposition, was not an accurate predictor of the effectiveness of the additives as cetane improvers. The effectiveness of a given additive appeared to correlate to the degree of molecular fragmentation rather than to thermal stability.

The fragments from 56 pipe bombs were collected (average recovery 87%), counted, weighed, sorted, and photographed. The matrix examined included eight energetic fillers, two initiation systems, three types of pipe, and several degrees of fill. The matrix and results are summarized in Table 1. For identical devices, the overall fragmentation pattern was surprisingly reproducible. The fragmentation patterns are presented in photos, but they are also reduced to numerical evaluators. A particularly useful evaluator is the fragment weight distribution map (FWDM) which describes explosive power with a single variable—the slope. This value is independent of device size and percent recovery. We believe this database of 56 pipe bombs is the largest controlled study of these devices. This study demonstrates the possibility that, even in circumstances where chemical residue cannot be found, sufficient evidence is present in the pipe fragments to identify the nature of the energetic filler.