Thermochemistry of N3O2-

Atmospheric pressure chemical ionization of explosives induced by soft X-radiation in ion mobility spectrometry: mass spectrometric investigation of the ionization reactions of drift gasses, dopants and alkyl nitrates

A promising replacement for the radioactive sources commonly encountered in ion mobility spectrometers is a miniaturized, energy-efficient photoionization source that produce the reactant ions via soft X-radiation (2.8 keV). In order to successfully apply the photoionization source, it is imperative to know the spectrum of reactant ions and the subsequent ionization reactions leading to the detection of analytes. To that end, an ionization chamber based on the photoionization source that reproduces the ionization processes in the ion mobility spectrometer and facilitates efficient transfer of the product ions into a mass spectrometer was developed. Photoionization of pure gasses and gas mixtures containing air, N₂ , CO₂ and N₂ O and the dopant CH₂ Cl₂ is discussed. The main product ions of photoionization are identified and compared with the spectrum of reactant ions formed by radioactive and corona discharge sources on the basis of literature data. The results suggest that photoionization by soft X-radiation in the negative mode is more selective than the other sources. In air, adduct ions of O₂^- with H₂ O and CO₂ were exclusively detected. Traces of CO₂ impact the formation of adduct ions of O₂^- and Cl^- (upon addition of dopant) and are capable of suppressing them almost completely at high CO₂ concentrations. Additionally, the ionization products of four alkyl nitrates (ethylene glycol dinitrate, nitroglycerin, erythritol tetranitrate and pentaerythritol tetranitrate) formed by atmospheric pressure chemical ionization induced by X-ray photoionization in different gasses (air, N₂ and N₂ O) and dopants (CH₂ Cl₂ , C₂ H₅ Br and CH₃ I) are investigated. The experimental studies are complemented by density functional theory calculations of the most important adduct ions of the alkyl nitrates (M) used for their spectrometric identification. In addition to the adduct ions [M + NO₃ ]^- and [M + Cl]^- , adduct ions such as [M + N₂ O₂ ]^- , [M + Br]^- and [M + I]^- were detected, and their gas-phase structures and energetics are investigated by density functional theory calculations. Copyright © 2016 John Wiley & Sons, Ltd.

Kinetic stability and propellant performance of green energetic materials

A thorough theoretical investigation of four promising green energetic materials is presented. The kinetic stability of the dinitramide, trinitrogen dioxide, pentazole, and oxopentazole anions has been evaluated in the gas phase and in solution by using high-level ab initio and DFT calculations. Theoretical UV spectra, solid-state heats of formation, density, as well as propellant performance for the corresponding ammonium salts are reported. All calculated properties for dinitramide are in excellent agreement with experimental data. The stability of the trinitrogen dioxide anion is deemed sufficient to enable synthesis at low temperature, with a barrier for decomposition of approximately 27.5 kcal mol(-1) in solution. Oxopentazolate is expected to be approximately 1200 times more stable than pentazolate in solution, with a barrier exceeding 30 kcal mol(-1), which should enable handling at room temperature. All compounds are predicted to provide high specific impulses when combined with aluminum fuel and a polymeric binder, and rival or surpass the performance of a corresponding ammonium perchlorate based propellant. The investigated substances are also excellent monopropellant candidates. Further study and attempted synthesis of these materials is merited.

Solvent resonance effect on the anisotropy of NO−(N2O)n cluster anion photodetachment

Photodetachment from NO(-)(N(2)O)(n) cluster anions (n< or =7) is investigated using photoelectron imaging at 786, 532, and 355 nm. Compared to unsolvated NO(-), the photoelectron anisotropy with respect to the laser polarization direction diminishes drastically in the presence of the N(2)O solvent, especially in the 355 nm data. In contrast, a less significant anisotropy loss is observed for NO(-)(H(2)O)(n). The effect is attributed to photoelectron scattering on the solvent, which in the N(2)O case is mediated by the (2)Pi anionic resonance. No anionic resonances exist for H(2)O in the applicable photoelectron energy range, in line with the observed difference between the photoelectron images obtained with the two solvents. The momentum-transfer cross section, rather than the total scattering cross section, is argued to be an appropriate physical parameter predicting the solvent effects on the photoelectron angular distributions in these cluster anions.

The negative ion chemistry of nitric oxide in the gas phase

Nitric oxide is not only an important biological molecule with varied indispensable physiological roles but also shows interesting chemical reactivity both in gas-phase and solution phase. Even though it is a small molecule with an extremely low electron affinity, the reactivity of NO in the gas-phase is not just limited to electron-transfer or adduct formation. NO can behave both as an electrophile with closed-shell anions or as a radical with open-shell anions. Its reactivity with open-shell anions is characteristic and varied leading to interesting rearrangements. Nitric oxide anion undergoes spin-forbidden proton transfer with strong acids. Also, the ability of NO to serve both as one-electron or three-electron donor ligand can result in adduct formation or substitution reactions with transition metal complexes.