Vibrational analysis of isopropyl nitrate and isobutyl nitrate

Raman and infrared spectra of isopropyl nitrate and isobutyl nitrate are reported. These spectra are used in combination with computational studies employing density functional theory at the B3-LYP/6-31G* level to assign the vibrational transitions to their corresponding normal coordinates. Similar to other alkyl nitrates, the frequency of the NO2 symmetric stretch remains relatively unchanged while the asymmetric stretch shifts to lower frequency with increasing alpha-carbon substitution. The mode assignments involving the photochemically relevant -ONO2 chromophore agree well with those from previous infrared work. Raman depolarization ratios are also presented, and provide evidence that the condensed phase, ground-state molecular structure of isobutyl nitrate is of Cs symmetry. In contrast, the minimum energy structure of isopropyl nitrate is predicted to contain a pronounced twist around the C-O bond relative to the Cs-symmetry structure that lies 2.6 kcal/mol higher in energy. Infrared intensities of isopropyl nitrate are consistent with the twisted geometry, demonstrating that this conformer is favored in solution.     

Anharmonic effects in ammonium nitrate and hydroxylammonium nitrate clusters

The covalent and ionic clusters of ammonium nitrate and hydroxyl ammonium nitrate are characterized using density functional theory and second-order vibrational perturbation theory. The most stable structures are covalent acid-base pairs for the monomers and ionic acid-base pairs for the dimers. The hydrogen-bonding distances are greater in the ionic dimers than in the covalent monomers, and the stretching frequencies are significantly different in the covalent and ionic clusters. The anharmonicity of the potential energy surfaces is found to influence the geometries, frequencies, and nuclear magnetic shielding constants for these systems. The inclusion of anharmonic effects significantly decreases many of the calculated vibrational frequencies in these clusters and improves the agreement of the calculated frequencies with the experimental data available for the isolated neutral species. The calculations of nuclear magnetic shielding constants for all nuclei in these clusters illustrate that quantitatively accurate predictions of nuclear magnetic shieldings for comparison to experimental data require the inclusion of anharmonic effects. These calculations of geometries, frequencies, and shielding constants provide insight into the significance of anharmonic effects in ionic materials and provide data that will be useful for the parametrization of molecular mechanical force fields for ionic liquids. Anharmonic effects will be particularly important for the study of proton transfer reactions in ionic materials.     

Thermal decomposition properties of guanidine nitrate and basic cupric nitrate

Characterized with a large gas production and low combustion temperature, the guanidine nitrate (GN) gas-generating agents are studied and applied widely. The determination factors of thermal decomposition properties of guanidine nitrate and basic cupric nitrate (GN/BCN) gas-generating agents for airbag application was investigated by the thermogravimetry–differential scanning calorimetry–mass spectrmetry–Fourier transform infrared spectroscopy (TG-DSC-MS-FTIR) and automatic calorimeter. Five different mass ratios were concerned. Our study showed that the onset reaction temperatures of GN/BCN mixtures were lower than that of individual GN and BCN. The thermal decomposition of GN/BCN mixtures could be divided into three stages, including the dissociation and escape of crystal water, solid (GN)-solid (BCN) phase reaction, and liquid (GN)-solid (BCN) phase reaction. When mass ratio of GN/BCN was 62.24/37.73, the largest value of the reaction heat was measured to 3152.7 J g^?1, with N₂ and H₂O as the major gases during thermal decomposition.     

Glycine sodium nitrate

The glycine mol­ecule in the title compound, Na(NO₃)·C₂H₅NO₂, exists in the zwitterionic form. The Na atom exhibits eightfold coordination and the polyhedron may be visualized as a distorted hexagonal bipyramid. The glycine mol­ecules are linked through head-to-tail hydrogen bonds and are found `sandwiched' between the Na(NO₃) layers.     

1-Silantranyl nitrate

A method of synthesis of 1-silatranyl nitrate O₂NOSi(OCH₂CH₂)₃N based on the reaction of 1-hydrosilatrane with mercury nitrate in the acetonitrile medium was developed. The structure of the synthesized 1-silatranyl nitrate, mp 227°C, was confirmed by elemental analysis, ¹H, ¹³C, and ²⁹Si NMR spectoscopy, infrared spectroscopy, and mass spectrometry. Silatranyl nitrate previously described in the literature as yellowish viscous oil apparently contains impurities preventing its crystallization.     

Thermochemical properties of l-alanine nitrate and l-alanine ethyl ester nitrate

Two inorganic derivatives of l-α-alanine, namely alanine nitrate (AlaNO₃) and alanine ethyl ester nitrate (AlaEthNO₃), were synthesized and studied by combustion calorimetry and differential scanning calorimetry (DSC). The enthalpies of combustion and formation in the condensed state, as well as the thermal behavior and stability in the temperature range of 25–250 °C for AlaNO₃ and ?70–250 °C for AlaEthNO₃, were determined. The increasing of the stability of the derivatives compared with that of the alanine was observed. The melting decomposition temperatures and the corresponding enthalpies of transitions were evidenced. FT-IR determinations were used to identify functional groups of the studied compounds. The UV–vis spectral study was carried out to test the optical transmitting property. Additional polarimetric measurements which confirmed the chiral nature of the two nitrates were performed.     

Far infrared spectra of methyl nitrate and methyl-d3 nitrate

The far infrared spectra from 300 to 50 cm⁻¹ of methyl nitrate, CH₃ONO₂, and methyl-d₃ nitrate, CD₃NO₂, have been recorded at a resolution of 0.12 cm⁻¹. The fundamental methyl torsional mode has been observed at 204.5 cm⁻¹ (154.2 cm⁻¹ for CD₃ONO₂) with two excited states falling to lower frequencies which gives a V₃ barrier of 980 ± 40 cm⁻¹ (2.80 ± 0.11 kcal/mol). The NO₂ torsion (methoxy) has been observed with the 1 ← 0 transition being at 133.7 cm⁻¹ (119.5 cm⁻¹ for CD₃ONO₂) and eight successive excited states falling to lower frequencies. From these data the twofold barrier to internal rotation has been calculated to be 2650 ± 75 cm⁻¹ (7.69 ± 0.21 kcal/mol).     

The heat of dissolution of uranyl nitrate in aqueous nitrate solutions

Conclusions A model has been suggested to explain the observed relationship between the measured heats of dissolution of uranyl nitrate in aqueous nitrate solutions and the concentration of the salting-out agent. The model describes the change in the structure of water in the solution with change in its concentration. On the one hand, a destruction of the water structure by ions occurs, which is weakened with increase in the distance from the ion, and leads to such irregularity in the distribution of water molecules in the solution that the mean number of molecules of water in unit volume is increased with increase in the distance from the ions. In experiments on the heat of dissolution this increase leads to increased hydration of the uranyl cation and reduction in the endothermicity of the dissolution with increase in the concentration of the solution. On the other hand, an interaction occurs between the ions of the salting-out agent and the water molecules in the solution, leading to the opposite result: There is an increase in the mean number of water molecules of the solution in unit volume in the direction of these ions. In experiments on the heat of dissolution this is revealed in the dehydration of the uranyl cation, and correspondingly in an increase in the endothermicity of the dissolution with increase in the concentration of the solution. The proposed model is in harmony with data on vapor pressure above the solutions (the relationship between the activity coefficient of the water and the concentration of the solution).Translated from Zhurnal Strukturnoi Khimii. Vol. 3, No. 2, pp. 143–150, March–April. 1962     

Thermal decomposition of ammonium nitrate dispersed in a multicomponent nitrate system

To obtain the kinetic curves of thermal decomposition of ammonium nitrate occurring together with decomposition of metal nitrates contained in a mixture, the ammonia contents evolved from samples heated under thermoanalytical conditions were determined by the Kjeldahl method.

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Zusammenfassung Der aus unter thermoanalytischen -Bedingungen erhitzten Proben freigesetzte Ammoniakgehalt wird durch das Kjeldahlverfahren bestimmt, um die kinetischen Kurven der thermischen Zersetzung von Ammoniumnitrat zusammen mit der Zersetzung von Metallnitraten in Gemischen zu erhalten.

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Determination of nitrate in agricultural material by the nitrate selective electrode

Summary When measuring nitrate in agricultural material (ensilage, dung etc.) extracted with copper sulphate solution with the nitrate selective electrode some of the samples were difficult to measure due to unstable readings and a gradually change in the calibration curve. These problems could easily be reduced by simply diluting the samples before measuring. To the diluted samples standards were added before measurement to keep the readings in the linear part of the calibration curve. In addition this dilution will increase the life time of the electrode.

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Nitratbestimmung in landwirtschaftlichem Material mit Hilfe der Nitrat-selektiven Elektrode

Zusammenfassung Bei der Messung von Nitrat in landwirtschaftlichem Material (Silage, Dung u.a.) mit Hilfe der Nitrat-selektiven Elektrode nach Extraktion mit Kupfersulfatlösung ergaben sich bei einigen Proben Schwierigkeiten wegen instabiler Anzeigen und allmählichen Veränderungen der Eichkurve. Diese Probleme konnten durch einfache Verdünnung vor der Messung reduziert werden. Zu den verdünnten Proben wurden vor der Messung Standards zugesetzt, um die Ablesungen innerhalb des linearen Teils der Eichkurve zu halten. Zusätzlich wird durch die Verdünnung die Lebensdauer der Elektroden erhöht.

     

Determination of nitrate and nitrite in mixtures with a nitrate ion electrode

A rapid method for the determination of nitrate and nitrite ions is described. The potential of a mixture of nitrate and nitrite was measured with a nitrate ion selective electrode. The nitrite in the mixture is then oxidized to nitrate with permanganate in acid solution, and the potential of the oxidized solution is also measured with the electrode. The fundamental equations for the response of the nitrate ion electrode to nitrate ion in the presence of interfering ions were used, and a new equation was developed for calculating the original nitrate concentration of the mixture. The absolute errors for solutions of known concentrations (2.5–100 p.p.m. each) were 1.8 p.p.m. nitrate and 2 p.p.m. nitrite. When the results are calculated by computer, five determinations can be performed in 30 min. The method was applied to the determination of the oxides of nitrogen in cigarette smoke as nitrite and nitrate after dissolution in basic solution.     

Photochemistry of adsorbed nitrate

In the atmosphere, gas-phase nitrogen oxides including nitric acid react with particle surfaces (e.g., mineral dust and sea salt aerosol) to yield adsorbed nitrate, yet little is known about the photochemistry of nitrate on the surface of these particles. In this study, nitrate adsorbed on alumina surfaces, a surrogate for mineral dust aerosol, is irradiated with broadband light (lambda > 300 nm) in the absence and presence of coadsorbed water, at <1% and 45 +/- 2% relative humidity (%RH), respectively, and molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products, NO2, NO, and N2O. Although NO2, NO, and N2O form under the different conditions investigated, both coadsorbed water and molecular oxygen change the gas-phase product distribution, with NO being the major product under dry and humid conditions in the absence of molecular oxygen and NO2 the major product in the presence of molecular oxygen. To the best of our knowledge, this is the first study to investigate the role of solvation by coadsorbed water in the photochemistry of adsorbates at solid interfaces and the roles that molecular oxygen, adsorbed water, and relative humidity may have in photochemical processes on aerosol surfaces that have the potential to alter the chemical balance of the atmosphere.     

Phase stabilization of ammonium nitrate by double addition of potassium nitrate and melamine

Methods for providing stabilization of ammonium nitrate and expanding the application field of this oxidizing agent in gas-generating compositions used for various purposes were sought for. The results of a study of the physicochemical properties of ammonium nitrate with a melamine–potassium nitrate double additive introduced by mechanical mixing and crystallization from an aqueous (nonaqueous) solution at the boiling point are presented. The phase diagrams of the ammonium nitrate–melamine and ammonium nitrate–melamine–potassium nitrate systems, based on the results of a differential-thermal analysis, demonstrated that a phase-stable ammonium nitrate can be formed by using the method of crystallization from an aqueous (nonaqueous) solution at the boiling point. The resulting samples were examined by IR spectroscopy and X-ray diffraction analysis, and a conclusion was made that a new thermodynamically stable phase can be formed in the system with individual additives, and the introduction of a double additive leads to a combined effect: a thermodynamically stable crystal structure is formed, with the simultaneous slowing down of the nucleation and growth of a new phase in the course of a phase transformation.