Energetic salts

Urea nitrate (UN), more properly called uronium nitrate, is an energetic salt, and as such would not be expected to have much vapour pressure however, it might be detectable due to evolved urea or nitrogen oxides. Detection of urea nitrate is essential because for over a decade it has been a frequent choice of terrorists. It was used in the bombing of the World Trade Center in New York City (Februaryl 993) and in many car bombings in Palestine. In 1992, the use of urea nitrate became so prevalent in bombings by the Shining Path that sales of urea were outlawed in Peru. 

Katritzky et al. have described synthetic routes toward l//-tetrazole-5-dinitromethylide sodium salt 618 <2005CHE111>. Energetic salts comprised of substituted tetrazolium cations and the 3,5-dinitro-l,2,4-triazolate anion, viz. 1,4,5-trimethyltetrazolium 3,5-dinitro-l,2,4-triazolate 619 and 4,5-dimethyl-l-aminotetrazolium 3,5-dinitro-1,2,4-triazolate 620, were obtained and characterized by Shreeve and co-workers <2005JMC3459>. 

C NMR spectra of 3-nitro-l,2,4-triazol-5-one and seven of its salts with different amines have been studied. The chemical shifts of C-3 and C-5 are independent of the nature of the cation (Table 3.21) [560], NMR spectra of 1-nitro-1,4-dihydro-1-7/-l,2,4-triazol-5-one, 5-(3-azido-l,2,4-triazol-3-yl)-3-nitro-l,2,4-triazoles [611], l-alkyl-3-nitro-l,2,4-triazol-5-one [612], some 3-nitro-2-methyl-l,2,4-triazolone derivatives [613-615], and their mono- and dinitro energetic salts [616] have been discussed. 

The vibration spectra of nitrated l,2,4-triazol-5-ones [611, 614, 615] and their energetic salts [616] are discussed. The thermal decomposition mechanism under rapid heating of thin films of 3-nitro-l,2,4-triazol-5-one was studied by pulsed infrared laser and Fourier-transform infrared spectroscopy [1071],... 

Xue H, Gao Y, Twamley B, et al. New energetic salts based on nitrogen-containing heterocycles. Chem. Mater. 2005. 17, 191-198. 

Hong Xue, Sean W, Arritt, Brendan Twamley, et al. Energetic salts from N-aminoazoles. Inorg. Chem. 2004. 43, 7972-7977. 

Xue H, Twamley B, Shreeve JM (2005) Energetic salts of substituted 1,2,4-triazolium and tetrazolium 3,5-dinitro-l,2,4-triazolates. J Mat Chem 15 3459-3465... 

Descriptions of classical and quantum mechanical methods for simulating energetic salts are presented. An overview of recent applications of these methods for predictions of gas-and condensed-phase properties, chemical reactivities, and phase transitions is given. The limitations and some suggestions for further developments of the methods are also discussed. 

Perhaps the most important aspect of energetic salts that needs to be understood for their energetic applications is the mechanisms of thermal decomposition. The immediate challenge is to use computations, since experimental measurements are in many cases not feasible, to determine the initial chemical reactions for various conditions, i.e., phase, temperature, and pressure. This is critical for understanding both combustion and detonation. Quantum chemistry methods can be used to compute bond-dissociation energies and transition-state... 

The selected results just presented demonstrate the kinds of information that can be obtained by using ab initio molecular orbital and DFT calculations. The studies to date have focused for the most part on structural and energetic properties of the various atomic, ionic, and molecular species that may be involved in the thermal decomposition of energetic salts. Also, theoretical calculations have been used to obtain quantitatively descriptions of the various elementary steps postulated in mechanisms of the dissociation processes of these salts and to predict the most probable initial steps. For both ADN and AP, quantum chemistry... 

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