- Heterogeneous kinetics of the uptake of ClONO2 on NaCl and KBr
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The uptake kinetics of ClONO2 on NaCl (reaction 1) and on KBr (reaction 2) have been studied in a low-pressure, Teflon-coated Knudsen reactor at room temperature. The initial uptake coefficient for both reactions has been measured as 0.23 ± 0.06 and 0.35 ± 0.06 for reactions 1 and 2, respectively, and is independent of reactant density in the range 1010-1013 molecules cm-3. The values of the uptake coefficients are independent of presentation of the salt substrates: identical results are obtained on powder, grains, single-crystal surfaces, and thin deposited salt layers. The only product of reaction 1 is Cl2. Reaction 2 initially produces Br2, followed by BrCl and Cl2. In our proposed mechanism, BrCl is the product of reaction 2, and secondary reactions between BrCl and the KBr substrate yield Br2 at short reaction times and Cl2 under prolonged exposure.
- Caloz, Francois,Fenter, Frederick F.,Rossi, Michel J.
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- Metal oxidation with N2O5: The nitrosylium nitrates (NO)Cu(NO3)3, (NO)2[Zn(NO3) 4] and (NO)6[Ni4(NO3) 12](NO3)2·(HNO3)
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The oxidation of copper, zinc and nickel by N2O5 led, respectively, to turquoise-coloured single crystals of (NO)Cu(NO 3)3 [monoclinic, P21/m, Z = 2, a = 465.90(5), b = 1111.7(1), c = 700.7(1) pm, β = 100.70(2)°, wR2 = 0.0566], light-yellow single crystals of (NO)2[Zn(NO 3)4] [orthorhombic, Fdd2, Z = 8, a = 1522.8(2), b = 2346.4(3), c = 596.18(7) pm, wR2 = 0.0452] and green single crystals of (NO)6[Ni4(NO3)12](NO 3)2·(HNO3) [orthorhombic, P2 12121, Z = 4, a = 1167.68(4), b = 1791.97(6), c = 1834.11(6) pm, wR2 = 0.0762]. In (NO)Cu(NO3) 3, the Cu2+ ion is coordinated by six oxygen atoms of monodentatenitrate groups in the form of a tetragonal distorted octahedron. The nitrate groups are connected to further copper ions leading to a two-dimensional network. In contrast, in (NO)2[Zn(NO3)4], the nitrate anions are coordinated to only one Zn2+, ion and the coordination polyhedron is a distorted octahedron. The complex nitrate (NO) 6[Ni4(NO3)12](NO3) 2·(HNO3) exhibits anionic ribbon chains according to ∞1{[Ni(NO3)1/1(NO 3)4/2]}22- with octahedrally coordinated Ni2+ ions as well as non-coordinating nitrate ions and HNO3 molecules. The thermal decomposition of the copper and zinc nitrates are multistep processes and lead to a mixture of Cu and Cu2O in the case of the copper compound and to ZnO for the zinc complex. Copyright
- Gagelmann, Steffen,Riess, Katja,Wickleder, Mathias S.
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- Infrared spectrum and theoretical study of the dinitrogen pentoxide molecule (N2O5) in solid argon
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Fourier Transform Infrared (FTIR) spectra of the covalent dinitrogen pentoxide molecule isolated in a solid argon matrix at 10 K are reported. The measured frequencies in the 200-4000 cm-1 region are in close agreement with gas phase values previously reported. An accurate and sophisticated ab initio study showed that the stable equilibrium structure, C2 symmetry, was in agreement with the structure previously determined by electron diffraction data.
- Bencivenni,Sanna,Schriver-Mazzuoli,Schriver
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- Temperature-Dependent Ultraviolet Absorption Spectrum for Dinitrogen Pentoxide
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The ultraviolet absorption cross sections for N2O5 are presented for wavelengths between 200 and 380 nm and for temperatures between 223 and 300 K.The absorption spectrum above 290 nm shows a pronounced temperature dependence.
- Yao, Francis,Wilson, Ivan,Johnston, Harold
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- Heterogeneous uptake of gaseous N2O5 by (NH4)2SO4, NH4HSO4, and H2SO4 aerosols
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The heterogeneous uptake of gaseous N2O5 by ammonium sulfate [(NH4)2SO4], ammonium bisulfate [NH4HSO4], and sulfuric acid [H2SO4] aerosols as a function of relative humidity has been investigated at room temperature and atmospheric pressure. Ammonium-containing aerosols were generated by a constant-output atomizer and conditioned by passing through a diffusion dryer. Sulfuric acid aerosols were produced by the homogeneous reaction of SO3 and H2O in a borosilicate vessel. Addition of a dry or wet N2 flow controlled the relative humidity (RH) of these aerosol flows. Using a chemical ionization mass spectrometer (CIMS) for N2O5 concentration monitoring and a scanning mobility particle spectrometer (SMPS) for aerosol characterization, reaction probabilities (γ) in the range of 0.001 to 0.1 for the uptake of N2O5 were determined as a function of RH. The results are expressed as follows: γ[(NH4)2SO4] = 2.79 × 10-4 + 1.30 × 10-4 × (RH) - 3.43 × 10-6 × (RH)2 + 7.52 × 10-8 × (RH)3, γ[NH4HSO4] = 2.07 × 10-3 - 1.48 × 10-4 × (RH) + 8.26 × 10-6 × (RH)2, and γ[H2SO4] = 0.052 - 2.79 × 10-4 × (RH). We suggest that the water content and phase in the ammonium-containing aerosols control the reactivity of N2O5 while liquid-phase ionic reactions primarily dominate the uptake in sulfuric acid aerosols.
- Kane, Sean M.,Caloz, Francois,Leu, Ming-Taun
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- Nitrate radical quantum yield from peroxyacetyl nitrate photolysis
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Peroxyacetyl nitrate (PAN, CH3C(O)OONO2) is a ubiquitous pollutant that is primarily destroyed by either thermal or photochemical mechanisms. We have investigated the photochemical destruction of PAN using a combination of laser pulsed photolysis and cavity ring-down spectroscopic detection of the NO3 photoproduct. We find that the nitrate radical quantum yield from the 289 nm photolysis of PAN is φNO3PAN = 0.31 ± 0.08 (±2σ). The quantum yield is determined relative to that of dinitrogen pentoxide, which is assumed to be unity, under identical experimental conditions. The instrument design and experimental procedure are discussed as well as auxiliary experiments performed to further characterize the performance of the optical cavity and photolysis system.
- Flowers, Bradley A.,Angerhofer, Mark E.,Simpson, William R.,Nakayama, Tomoki,Matsumi, Yutaka
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- Reactive uptake of N2O5 on aqueous H 2so4 solutions coated with 1-component and 2-component monolayers
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Reactive uptake of N2O5 on aqueous sulfuric acid solutions was studied in the presence of 1-component (octadecanol) and 2-component (octadecanol + phytanic acid) monolayers. In the 1-component monolayer experiments, the reactive uptake coefficient depended strongly on the molecular surface area of the surfactant. Also, the 1-component monolayer showed significant resistance to mass transfer even when the fractional surface coverage of the surfactant was less than 1. For example, a monolayer of 1-octadecanol with a fractional surface coverage of 0.75 decreased the reactive uptake coefficient by a factor of 10. This is consistent with previous studies. In the 2-component monolayer experiments, the reactive uptake coefficient depended strongly on the composition of the monolayer. When the monolayer contained only straight-chain molecules (1-octadecanol), the reactive uptake coefficient decreased by a factor of 42 due to the presence of the monolayer. However, when the monolayer contained 0.20 mole fraction of a branched surfactant (phytanic acid) the reactive uptake coefficient only decreased by a factor of 2. Hence, a small amount of branched surfactant drastically changes the overall resistance to reactive uptake. Also, our results show that the overall resistance to reactive uptake of 2-component monolayers can be predicted reasonably accurately by a model that assumes the resistances to mass transfer can be combined in parallel.
- Cosman,Bertram
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- Kinetics of ClONO2 reactive uptake on ice surfaces at temperatures of the upper troposphere
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The reactive uptake kinetics of ClONO2 on pure and doped water-ice surfaces have been studied using a coated wall flow tube reactor coupled to an electron impact mass spectrometer. Experiments have been conducted on frozen film ice surfaces in the temperature range 208-228 K with P ClONO2 ≤ 10-6 Torr. The uptake coefficient (γy) of ClONO2 on pure ice was time dependent with a maximum value of γmax ~0.1. On HNO3-doped ice at 218 K the γmax was 0.02. HOCl formation was detected in both experiments. On HCl-doped ice, uptake was gas-phase diffusion limited (γ > 0.1) and gas-phase Cl2 was formed. The uptake of HCl on ice continuously doped with HNO3 was reversible such that there was no net uptake of HCl once the equilibrium surface coverage was established. The data were well described by a single site 2-species competitive Langmuir adsorption isotherm. The surface coverage of HCl on HNO3-doped ice was an order of magnitude lower than on bare ice for a given temperature and PHCl. ClONO2 uptake on this HCl/HNO3-doped ice was studied as a function of PHClHci. γmax was no longer gas-phase diffusion limited and was found to be linearly dependent on the surface concentration of HCl. Under conditions of low HCl surface concentration, hydrolysis of ClONO2 and reaction with HCl were competing such that both Cl2 and HOCl were formed. A numerical model was used to simulate the experimental results and to aid in the parametrization of ClONO2 reactivity on cirrus ice clouds in the upper troposphere.
- Fernandez, Miguel A.,Hynes, Robert G.,Cox, Richard A.
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- Rate Constants for Reactions between Atmospheric Reservoir Species. 1. HCl
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The kinetics of the reactions of HCl with ClONO2, N2O5, O3, and HO2NO2 have been investigated by using a large-volume static reactor and a Fourier transform spectrometer (FTIR) at 296 K.The upper limits for the homogenous gas-phase reaction rates of the ClONO2 + HCl, N2O5 + HCl, O3 + HCl, and HO2NO2 + HCl reactions were found to be 8.4 x 10-21, 8.4 x 10-21, 4.7 x 10-24, and 9.0 x 10-22 (all in unit of cm3 s-1), respectively.The heterogeneous nature of the ClONO2 + HCl and N2O5 + HCl reactions are characterized in terms of the Langmuir-Rideal mechanism.The yields of HNO3 were be observed to be 0.94 +/- 0.14 and 1.10 +/- 0.12 for the ClONO2 + HCl and N2O5 + HCl reactions, respectively, and the yield of ClNO2 was found to be 0.84 +/- 0.10 for the N2O5 + HCl reaction.The quoted errors represent one standard deviation of the measurement.In addition, an upper limit of 1.6 x 10-19 cm3 s-1 at 296 K for the reaction of NO3 with HCl was also obtained in this study.These results may be important in the elucidation of the role played by heterogeneous reactions in the development of the springtime Antarctic ozone depletion over the past decade.
- Leu, Ming-Taun,Hatakeyama, Shiro,Hsu, Kuang-Jung
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- A Fourier Transform Infrared Study of the Rate Constant of the Homogeneous Gas-Phase Reaction N2O5 + H2O and Determination of Absolute Infrared Band Intensities of N2O5 and HNO3
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N2O5 was reacted with water vapor in large FEP-Teflon bags and its decay followed by samplig in a White gas cell using infrared Fourier transform spectroscopy.A rate constant for the homogeneous N2O5 + H2O gas-phase reaction at 296 +/- 2 K and 740 Torr total pressure equel to (1.48 +/- 0.42)E-21 cm3/molecule*s was observed.Critical analysis of the results suggested that the true homogeneous rate constant might be lower.The measured HNO3 absolute intensities of the overlapping band systes $v5, 2$v9 and $v5 + $v9 - $v9 (840-930/cm) and $v3,$v4 (1270-1350/cm) were 2.21E-17 and 4.29E-17 cm/molecule, respectively.
- Hjorth, J.,Ottobrini, G.,Cappellani, F.,Restelli, G.
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- N2O5 reactive uptake on aqueous sulfuric acid solutions coated with branched and straight-chain insoluble organic surfactants
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A flow reactor coupled to a chemical ionization mass spectrometer was used to study the reactive uptake coefficients at 273 K of N2O5 on aqueous 60 wt % sulfuric acid solutions coated with insoluble organic monolayers. Both straight-chain surfactants (1-hexadecanol, 1-octadecanol, and stearic acid) and a branched surfactant (phytanic acid) were studied. The reactive uptake coefficient decreased dramatically for straight-chain surfactants. The decrease ranged from a factor of 17 to a factor of 61 depending on the type of straight-chain surfactant. In contrast to the straight-chain data, the presence of phytanic acid did not have a significant effect on the N2O5 reactive uptake coefficient (the decrease was less than the uncertainty in the data) compared to the uncoated solution. In addition to measuring the reactive uptake coefficients, we also investigated the relationship between properties of the monolayers and the reactive uptake coefficients. The reactive uptake coefficients measured on aqueous sulfuric acid subphases showed a relationship to the surface area occupied by the surfactant molecules. However, data obtained with other subphases did not overlap with this trend.
- Cosman,Knopf,Bertram
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- Aerosol chamber study of optical constants and N2O5 uptake on supercooled H2so4/H2O/HNO3 solution droplets at polar stratospheric cloud temperatures
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The mechanism of the formation of supercooled ternary H2SO 4/H2O/HNO3 solution (STS) droplets in the polar winter stratosphere, i.e., the uptake of nitric acid and water onto background sulfate aerosols at T a simulation experiment at the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. Supercooled sulfuric acid droplets, acting as background aerosol, were added to the cooled AIDA vessel at T = 193.6 K, followed by the addition of ozone and nitrogen dioxide. N2O5, the product of the gas phase reaction between O3 and NO2, was then hydrolyzed in the liquid phase with an uptake coefficient γ(N2O5). From this experiment, a series of FTIR extinction spectra of STS droplets was obtained, covering a broad range of different STS compositions. This infrared spectra sequence was used for a quantitative test of the accuracy of published infrared optical constants for STS aerosols, needed, for example, as input in remote sensing applications. The present findings indicate that the implementation of a mixing rule approach, i.e., calculating the refractive indices of ternary H2SO4/H2O/HNO3 solution droplets based on accurate reference data sets for the two binary H2SO4/H2O and HNO3/H2O systems, is justified. Additional model calculations revealed that the uptake coefficient γ(N2O5) on STS aerosols strongly decreases with increasing nitrate concentration in the particles, demonstrating that this so-called nitrate effect, already well-established from uptake experiments conducted at room temperature, is also dominant at stratospheric temperatures.
- Wagner, Robert,Naumann, Karl-Heinz,Mangold, Alexander,Moehler, Ottmar,Saathoff, Harald,Schurath, Ulrich
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- Promotional effect of spherical alumina loading with manganese-based bimetallic oxides on nitric-oxide deep oxidation by ozone
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Nitric oxide (NO) deep oxidation to dinitrogen pentoxide (N2O5) by ozone together with wet scrubbing has become a promising technology for nitrogen-oxide (NOx) removal in industrial boilers. Catalysts were introduced to enhance the N2O5 formation rate with less ozone injection and leakage. A series of monometallic catalysts (manganese, cobalt, cerium, iron, copper, and chromium) as prepared by the sol-gel method were tested. The manganese oxides achieved an almost 80% conversion efficiency at an ozone (O3)/NO molar ratio of 2.0 in 0.12 s. The crystalline structure and porous parameters were determined. The thermodynamic reaction threshold of NO conversion to N2O5 is oxidation with an O3/NO molar ratio of 1.5. Spherical alumina was selected as the support to achieve the threshold, which was believed to improve the catalytic activity by increasing the surface area and the gas-solid contact time. Based on the manganese oxides, cerium, iron, chromium, copper, and cobalt were introduced as promoters. Cerium and iron improved the deep-oxidation efficiency compared with manganese/spherical alumina, with less than 50 mg/m3 of outlet NO + nitrogen oxide, and less than 25 mg/m3 of residual ozone at an O3/NO molar ratio of 1.5. The other three metal oxides inhibited catalytic activity. X-ray diffraction, nitrogen adsorption, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy results indicate that the catalytic activity is affected by the synergistic action of NOx oxidation and ozone decomposition.
- Lin, Fawei,Wang, Zhihua,Shao, Jiaming,Yuan, Dingkun,He, Yong,Zhu, Yanqun,Cen, Kefa
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- Atom-efficient electrophilic aromatic nitration by dinitrogen pentoxide catalysed by zirconium(IV) 2,4-pentanedionate
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An atom-efficient, non-acidic, catalytic process is described for the nitration of electron deficient arenes such as o-nitrotoluene using a dinitrogen pentoxide-zirconium(IV) 2,4-pentanedionate system in dichloromethane solvent. Kinetic studies showed the nitration process to be first-order with respect to the aromatic substrate and higher than first-order with respect to the catalyst. Addition of the catalyst at ca. 0.1-1 mol% compared with both N2O5 and the organic substrate results in an increase in the first-order rate constant for nitration by a factor of approximately 5000 with a turnover number of at least 500. The orientation of the nitration products (2,4-/2,6-dinitrotoluenes) is consistent with attack of nitronium ion. The apparently high order of reaction with respect to the catalyst suggests a possible heterogeneous process.
- Hill, Adrian J.,Millar, Ross W.,Sandall, John P.B.
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- Superacids as catalysts of the oxidation of inorganic substrates
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The oxidation of sulfur dioxide, nitrogen dioxide, carbon monoxide, etc., in anhydrous trifluoroacetic acid (TFA) at room temperature was observed. The oxidative ability of anhydrous TFA in reactions with inorganic substances was shown to be related to molecular oxygen dissolved in it. The dissolved molecular oxygen endowed TFA with the properties of a superacid with pK a ? -12. Mechanisms of active oxygen reactions with inorganic substrates were suggested. Pleiades Publishing, Inc., 2006.
- Vishnetskaya,Yakimova,Sidorenkova
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- Synthesis and Mid-IR Absorption Cross Sections of BrNO2
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A method for the synthesis of gaseous BrNO2 at concentrations of the order of 1E-9 mol/cm3 at atmospheric pressure is described, based on the heterogeneous reaction of ClNO2 with aqueous bromide solutions.We measured the gas-phase infrared absorption cross sections in the range 700-1800 cm-1.The matrix isolation spectrum was recorded for identification by comparison with literature data.
- Frenzel, Andreas,Scheer, Volker,Behnke, Wolfgang,Zetzsch, Cornelius
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- Physicochemical characterization of the decomposition course of hydrated ytterbium nitrate: Thermoanalytical studies
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Yb(NO3)3·6H2O was used as a parent compound for the formation of Yb2O3 at up to 800°C in atmosphere of air. Thermal processes occurring during the decomposition course were monitored by means of differential thermal analysis (DTA), thermogravimetry (TG), and the gaseous decomposition products were identified by mass spectrometry (GC-MS). The intermediates and final solid products were characterized by IR-spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that, Yb(NO3) 3·6H2O decomposes completely through 11 endothermic mass loss processes. The dehydration occurs through the first six steps at 95, 145, 165, 175 and 200°C, forming crystalline nitrate Yb(NO3) 3, which decomposes to YbO0.5(NO3)2 at 250°C. The latter, decomposes to non-stoichiometric unstable intermediate YbO0.75(NO3)1.5 at 335°C, which decompose immediately to a stable and crystalline YbONO3 at 365°C, then to a non-stoichiometric unstable intermediate Yb(O)1.25(NO 3)0.5 at 470°C. Finally, Yb2O3 was formed at 510°C. The decomposition course and surface morphology were supported and followed by SEM and textural studies (SBET).The final product Yb2O3 at 600°C has a large irregular sheet shaped particles containing a large pores, voids and cracks and has S BET=45 m2/g. The gaseous decomposition products are water vapor, nitric acid and nitrogen oxides (NO, NO2 and N 2O5). The activation energy (ΔE in kJ/mol) was calculated non-isothermally for each thermal processes.
- Balboul, Basma A.A.
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- A kinetic study of gas-phase reaction of thiophene with NO3 by using absolute and relative methods
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The gas-phase rate coefficient for the reaction of thiophene with nitrate radical, NO3, has been determined, using relative (gas chromatography as analytical tool) and absolute methods at 298 K. The absolute experiments were carried out using a fast-flow-discharge technique, with detection of the NO3 radical by Laser Induced Fluorescence (LIF). The proposed rate coefficient at 298 K is, k = (3.16 ± 0.27) × 10-14 cm3 molecule-1 s-1. The temperature dependence was studied by the absolute technique in the range 260-433 K, observing that in the interval of 260-277 K the rate coefficient decreases as the temperature increases and from 298 K onwards the rate coefficient increases with temperature.
- Caba?as,Martín,Salgado,Baeza,López,Martínez
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- Electrochemical synthesis of N2O5 by oxidation of N2O4 in nitric acid with PTFE membrane
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Electrochemical synthesis of dinitrogen pentoxide (N2O5) by oxidation of dinitrogen tetroxide (N2O4) in a plate-and-frame electrolyzer was investigated. As the separator, different porous polytetrafluoroethylene (PTFE) membranes were tested in this process and the effects of hydrophilicity and of hydrophobicity on the electrolysis were discussed. The transport of N2O4 and water from catholyte to anolyte through membrane occurred in the electrolysis, especially at the end of the electrolysis. The water transport had a much more effect on the electrolysis than that of the N2O4 diffusion. The hydrophobic PTFE membranes had better performance on control of water transport from catholyte to anolyte than that of the hydrophilic ones. Hydrophobicity can increase the chemical yield of N2O5. The membranes with a low hydrophobic surface were preferred. All the hydrophobic PTFE membranes with low resistance have the specific energy of 1.1-1.5 kWh kg-1 N2O5. The current efficiency of 67.3-80.2% and chemical yield of 58.9-60.9% were achieved in production of N2O5. The technique of replacing the catholyte with fresh nitric acid can minimize the transport of N2O4 and water to a great extent, it can further improve the chemical yield and reduce the specific energy.
- Wang, Qingfa,Su, Min,Zhang, Xiangwen,Wang, Li,Wang, Jixiao,Mi, Zhentao
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- Study of the pressure dependence of the rate constant of the reaction of NO3 with NO2
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We have applied time resolved cavity ring-down spectroscopy to a kinetic study of the reaction of NO3 with NO2 in 20-700 Torr of N2 diluent at 298 and 283 K. By fitting the data to Troe's expression with Fc = 0.6, the low-pressure and high-pressure limiting rate constants of this reaction were determined to be k1low(298 K) = (3.1 ± 0.8) × 10-30 cm6 molecule-2 s -1 and k1high(298 K) = (1.6 ± 0.3) × 10-12 cm3 molecule-1 s-1. These rate constants thus determined were 10-40% larger than those recommend in the NASA/JPL database.
- Nakano, Yukio,Sadamori, Kengo,Hosho, Yuichi,Ishiwata, Takashi
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- Crystal structures of nitronium tetranitratogallate and its reversible solid-state phase transition mediated by nonmerohedral twinning
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Single-crystal X-ray crystallographic analyses of [NO2][Ga(NO3)4] reveal that it undergoes a reversible phase transition without any apparent damage to the crystal during repeated temperature cyclings. The room-temperature, noncentrosymmetric, body-centered tetragonal (I 4), polymorph 1 (a = 9.2774(3) A, c = 6.1149(2) A, Z = 2) consists of well-separated nitronium and tetranitratogallate ions. The [Ga(NO3)4]- units exhibit a slightly squashed tetrahedral geometry in which all of the ligands are monodentate. Below approximately 250 K, distortions lower the symmetry to the chiral, body-centered monoclinic nonstandard space group I2. Both components (2a: a = 9.5857(2) A, b = 5.9399(1) A, c = 8.9759(2) A, β = 90.409(1)°, Z = 2. 2b: a = 9.5898(2) A, b = 5.9376(1) A, c = 8.9784(1) A, β = 90.420(1)°, Z = 2) of the nonmerohedrally twinned structure are independently refined and found to be enantiomeric with nearly identical distance and angle parameters. As in the high-temperature polymorph, the cations and anions are well separated. The most notable change involves two of the nitrato ligands in the [Ga(NO3)4]- ions that have become bidendate, causing the molecular structure to distort toward octahedral geometry.
- Colombo, Daniel G.,Young Jr., Victor G.,Gladfelter, Wayne L.
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- Electron irradiation of solid nitrous oxide
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We report the results of chemical processing induced by 1 keV electron irradiation of a solid N2O ice sample formed at 25 K. Ozone and several oxides of nitrogen (NO2, N2O2, N2O3, N2O4 and N2O5) were observed to form during the irradiation period. Such reactions have important implications for the ice chemistry of outer solar system planets/satellites and interstellar ices.
- Sivaraman,Ptasinska,Jheeta,Mason
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- Thermolabile noble metal precursors: (NO)[Au(NO3)4], (NO)2[Pd(NO3)4], and (NO) 2[Pt(NO3)6]
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Oxidizing noble metals: Pure N2O5 can oxidize elemental gold and palladium. The complex nitrates obtained by these reactions, (NO)[Au(NO3)4], (NO)2[Pd(NO3) 4], and also the first nitrate of tetravalent platinum, (NO) 2[Pt(NO3)6] (see picture for the anion: Pt-gray, N-green, O-blue), have the potential to act as precursors owing to their high thermolability. The thermal decomposition of (NO)[Au(NO 3)4] was elucidated in detail by several methods. Copyright
- Wickleder, Mathias S.,Gerlach, Frauke,Gagelmann, Steffen,Bruns, Joern,Fenske, Mandus,Al-Shamery, Katharina
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- Reaction of N2O5 with H2O on Carbonaceous Surfaces
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The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (γ=3*10-3) together with a redox reaction generating mostly NO.Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 10-4 Torr.In the presence of H2O, the same processes with γ=5*10-3 are observed.The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction.The rate law for HNO3 generation was found to be d/dt=kbi with kbi, the effective bimolecular rate constants, for 10 mg of carbon being (1.6+/-0.3)*10-13 cm3/s.
- Brouwer, L.,Rossi, M. J.,Golden, D. M.
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- Broadband cavity ringdown spectroscopy of the NO3 radical
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Cavity ringdown spectroscopy (CRDS) has been demonstrated using a broadband (20 nm) laser source and a two-dimensional clocked detector array. Absorption spectra of dilute samples (50-500 parts per trillion) of the nitrate radical, NO3, have been obtained between 650 and 670 nm by monitoring simultaneously the time and wavelength resolved output of a ringdown cavity. The potential of broadband CRDS for making measurements on samples containing multiple absorbers (e.g., atmospheric samples) is shown by applying analysis methods from differential optical absorption spectroscopy to quantify the NO3 concentration in the presence of nitrogen dioxide impurities.
- Ball, Stephen M.,Povey, Ian M.,Norton, Emily G.,Jones, Roderic L.
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- Protonation-induced ligand switching within NO2+ bound clusters
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An intracluster proton-promoted reaction leading to a ligand switching in mixed NO2+ complexes of nitric acid and its derivatives is described. The proton affinity and the NO2+ binding energy are demonstrated to be the factors affecting the process, the trend of which is shown to reflect the peculiar properties of nitric acid and its derivatives.
- De Petris, Giulia,Pepi, Federico
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- Relative reaction rates of HCHO, HCDO, DCDO, H13CHO, and HCH18O with OH, Cl, Br, and NO3 radicals
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Formaldehyde (HCHO) is a principal intermediate in the photochemical oxidation of hydrocarbons in the troposphere. Isotopic analysis is an important tool for tracing the atmospheric path of gaseous species, and for this purpose, characterization of the isotope effects in the loss processes for formaldehyde is needed. The main loss pathways for formaldehyde in the atmosphere are photolysis and reactions with the radical species of OH, Cl, Br, and NO 3. In this study, the kinetic isotope effects in the reactions of five different isotopomers of formaldehyde (HCHO) with OH, Cl, Br, and NO 3 radicals are studied in a relative-rate experiment at 298 ± 2 K and 1013 ± 10 mbar. The reaction rates of DCDO, HCDO, H 13CHO, and HCH18O with the four radicals are measured relative to H2CO in a smog chamber using long-path FTIR detection. The experimental data are analyzed with a nonlinear least-squares spectral-fitting method using measured high-resolution infrared spectra and cross sections from the HITRAN database. The reaction rates of HCDO and HCH 13O with OH and Cl are determined relative to HCHO as k OH+HCHO/kOH+HCDO = 1.28 ± 0.01, k OH+HCHO/kOH+HCH18O = 0.967 ± 0.006, k Cl+HCHO/kCl+HCDO = 1.201 ± 0.002, and k Cl+HCHO/kCl+HCH18O = 1.08 ± 0.01. The reaction rates of HCDO and HCH18O with Br and NO3 are determined relative to HCHO as kBr+HCHO/kBr+HCDO = 3.27 ± 0.03, k Br+HCHO/kBr+HCH18O = 1.275 ± 0.008, k NO3+HCHO/kNO3+HCDO = 1.78 ± 0.01, and k NO3+HCHO/kNO3+HCH18O = 0.98 ± 0.01. The errors represent 2σ from the statistical analyses, and do not include possible systematic errors.
- Fellberg, Karen L.,Johnson, Matthew S.,Nielsen, Claus J.
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- Photolysis of Chlorine Nitrate at 254 nm
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The photolysis of ClONO2 has been studied at 254 nm.The production of NO3, NO2, and ClONO and the removal of ClONO2 have been obseved directly, and the yield of O(3P) has been inferred from the production of O3.The production of Cl and NO3 was found to be the dominant photolysis pathway.For ClONO2 concentrations of 5*1013 molecules cm-3, the values determined for the quantum yields for the removal of ClONO2, -ψClONO2, and the production of NO3, ψNO3, were 0.99+/-0.1 and 1.04+/-0.04, respectively.However, these yields appear to be dependent on the ClONO2 concentration and decrease as ClONO2 concentration increases.For ClONO2 concentrations in the range (3-8)*1014 molecules cm-3, the yields, obtained for the formation of O, NO2, and ClONO, are ψO=0.24, ψNO2=0.25, and ψClONO0.2.No evidence was found for a significant production of NO.The observed behavior may be explained by the production of a long-lived excited state of ClONO2.The results are discussed in relation to the stratospheric behavior of ClONO2.
- Burrows, J. P.,Tyndall, G. S.,Moortgat, G. K.
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- Pressure-Dependent Yields and Product Branching Ratios in the Broadband Photolysis of Chlorine Nitrate
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The photolysis of chlorine nitrate was studied using broadband flash photolysis coupled with long-path ultraviolet-visible absorption spectroscopy.Branching ratios for the Cl + NO3 and ClO + NO2 product channels were determined from time-dependent measurements of ClO and NO3 concentrations.Yields of the ClO and NO3 products displayed a dependence on the bath gas density and the spectral distribution of the photolysis pulse.Product yields decreased with increasing bath gas density regardless of the spectral distribution of the photolysis pulse; however, the decrease in product yield was much more pronounced when photolysis was limited to longer wavelengths.For photolysis in a quartz cell (λ > 200 nm) the yield decreased by a factor of 2 over the pressure 10-100 Torr.In a Pyrex cell (λ > 300 nm), the yield decreased by a factor of 50 over the same pressure range.When photolysis was limited to λ > 350 nm, the yield decreased by a factor of 250.Branching ratios for the photolysis channels ClO + NO2 (1a) and ClONO2 + hν -> Cl + NO3 (1b) were determined from the relative ClO and NO3 product yields at various pressures.Although the absolute product yield displayed a pressure dependence, the branching between the two channels was independent of pressure.The relative branching ratios (assuming negligible contributions from other channels) are 0.61 +/- 0.20 for channel 1a and 0.39 +/- 0.20 for channel 1b for photolysis with λ > 200 nm and 0.44 +/- 0.08 for channel 1a and 0.56 +/- 0.08 for channel 1b for photolysis with λ > 300 nm.The implications of these results for the chemistry of the lower stratosphere are discussed.
- Nickolaisen, Scott L.,Sander, Stanley P.,Friedl, Randall R.
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- Rate constants for the collisional dissociation of N2O5 by N2
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The rate constants for the collisional dissociation of N2O5 by N2 are measured over the pressure and temperature ranges of 10 to 800 Torr and 285 to 384 K, respectively.The measurements are carried out in flow-through reaction cells of different volumes, the N2O5 being detected by selected ion-molecule reactions in a flowing afterglow apparatus.The present rate constants are somewhat smaller than those of earlier studies and also suggest that the transition from second- to first-order kinetics occurs at lower pressures than was earlier thought.The data are fitted to theoretical models of varying sophistication.The recommended values for use in extrapolation for the limiting low-pressure and high-pressure rate constants corresponding to the first-order Troe extension of the Lindeman-Hinshelwood model for FcentSC=0.572 are k0=1.15*10-5 exp(-19.70 kcal/mol/RT) cm3 s-1 and k=1.21*1017 exp(-25,41 kcal/mol/RT) s-1.Other forms yield similar results.
- Viggiano, A. A.,Davidson, J. A.,Fehsenfeld, F. C.,Ferguson, E. E.
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- A Low-Temperature Infrared Study of the Reactions of the Stratospheric NOy Reservoir Species Dinitrogen Pentoxide with Water Ice, 80-160 K
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The low-temperature chemistry of thin films of water ice and the important stratospheric NOy species dinitrogen pentoxide have been investigated in order to spectroscopically characterize one of the principlal heterogeneous reactions that occurs on polar stratospheric cloud particles(PSCs).This contributes to stratospheric denitrification.Using reflection-absorption infrared spectroscopy, we have observed the formation of both covalent and ionic forms of solid N2O5 on both ice and the clean substrate.Thermal evolution experiments suggest that the solid covalent phase, which can only be formed at the lowest temperatures (Ta surface layer of hydroxonium ions, solvated nitrate ions, and molecular nitric acid.Annealing to 160 K introduces more water into the surface layer by diffusion and produces a further reaction of the excess NO2+ and results in the formation of more molecular nitric acid.Some of the water reacts with molecular nitric acid to form an amorphous hydrate (H2O)n*H3O+NO3-.From this, we conclude that only N2O5 in the gas-phase covalent form reacts readily with ice and consequently that the reaction in the stratosphere is likely to involve the interaction between the gas phase and the ice surface and not a solid-solid interfacial one.The reaction of gas-phase N2O5 with a nitrate-containing ice surface and the competition between surface species for excess water has important implications for different N2O5 chemistry on type I (NAT and type II (ice) PSC particles.
- Horn, Andrew B.,Koch, Thomas,Chesters, Michael A.,McCoustra, Martin R. S.,Sodeau, John R.
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- Absorption Spectrum of NO3 and Kinetics of the Reactions of NO3 with NO2, Cl, and Several Stable Atmospheric Species at 298 K
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The absorption spectrum of NO3 has been measured between 615 and 670 nm in the photolysis of Cl2-ClONO2-N2 and F2-HNO3-N2 mixtures.The absorption cross section was found to be (1.19 +/- 0.36) x 10-17 cm2 molecule-1 at 622.3 nm, and this leads to a value of (1.85 +/- 0.56) x 10-17 cm2 molecule-1 at 662 nm in good agreement with most recent studies.The rate coefficient for the reaction NO3 + NO2 -> N2O5 was measured to be (4.8 +/- 0.3) x 10-13 and (5.8 +/- 0.8) x 10-13 cm3 molecule-1 at total pressures of 24 and 40 torr of N2, respectively.A rate coefficient for the reaction between Cl and NO3 was derived from the NO3 behavior in the photolysis of Cl2 and ClONO2 mixtures and its value at 298 K is (2.7 +/- 1.0) x 10-11 cm3 molecule-1 s-1.In addition, upper limits were determined for the rates of reaction of NO3 with SO2, CO, CH4, H2O2, and CS2.
- Burrows, J. P.,Tyndall, G. S.,Moortgat, G. K.
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- Thermal genesis course and characterization of praseodymium oxide from praseodymium nitrate hydrate
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Pr(NO3)3·6H2O was used as a precursor to produce PrO1.833 at 600°C in an atmosphere of static air. Thermal processes occurred were monitored by means of thermogravimetry, differential thermal analysis and mass spectrometry. IR-spectroscopy and X-ray characterized the intermediates and final solid products. The results showed that, Pr(NO3)3·6H2O decomposes through 11 endothermic weight loss processes. Five dehydration steps occurred at 130, 180, 200, 230 and 250°C, leading to the formation of crystalline nitrate monohydrate, Which decomposes to Pr(NO3)2 at 340°C. The latter, decomposes to PrO1.833 at 465°C, via four different intermediates PrO(NO3) at 430°C, and nonstoichiometric unstable, PrO0.25(NO3)2.5 at 362°C; Pr(O)0.5(NO3)2 at 382°C and Pr(O)0.75(NO3)1.5 at 400°C. The gaseous decomposition products identified by mass spectroscopy were water vapor and nitrogen oxides (NO, NO2 and N2O5). The activation energy was determined nonisothermally for the thermal processes monitored throughout the decomposition course. The final product PrO1.833 has a surface area of 46.3 m2/g.
- Hussein,Balboul,A-Warith,Othman
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- Temperature and Pressure Dependence of the Rate Coefficient for the Reaction NO3 + NO2 + N2 -> N2O5 + N2
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A discharge flow tube experiment has been conducted to determine the rate coefficient, k2, for reaction (2): NO3 + NO2 + N2 -> N2O5 + N2 from 236 to 358 K and 0.5 to 8 Torr.This represents the first study of the temperature dependence of k2 at low pressure, i.e. under conditions relevant to the middle and upper stratosphere.The data obtained here have been combined with other measurements of k2 and the following fall-off parameters are recommended: k0 = (2.8 +/- 0.4) x 10-30 (T/300)(-3.5 +/- 0.5) cm6 s-1, kinfinite = (1.66 +/- 0.25) x 10-12 (T/300)(0.2 +/- 0.2) cm3 s-1, for Fc = 2.5 exp(-1950/T) + 0.9 exp(-T/430).
- Orlando, John J.,Tyndall, Geoffrey S.,Cantrell, Christopher A.,Calvert, Jack G.
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- Photochemistry of dinitrogen pentaoxide in low-temperature matrices
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A combination of matrix isolation and FTIR spectroscopy has been employed to investigate the low-temperature photochemistry (4.2 K) of dinitrogen pentaoxide. UV photolysis of the matrix isolated precursor (MR = 1/1000) at λ > 230 nm resulted in the photoreduction of N2O5 to N2O via N2O3 as an intermediate. Both, asym- and sym-N2O3 were formed in argon matrices, whereas in solid nitrogen only asym-N2O3 was produced. Little or no evidence for the formation of isomeric forms of N2O4 was found. Possible photochemical pathways are discussed.
- Koch, Thomas G.,Sodeau, John R.
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- Hydrolysis of N2O5 on submicron sulfuric acid aerosols
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The hydrolysis of N2O5 on the surfaces of aerosol particles and cloud droplets is the dominant removal channel for NOx at night. Thus, it is important in determining the oxidative capacity of the atmosphere as the concentrations of NOx strongly affect the rate of tropospheric O3 formation. NOx levels in the stratosphere were depleted due to hydrolysis of N2O5 on the large quantity of sulfuric acid aerosol generated by volcanic gases. The kinetics of reactive uptake of gaseous N2O5 on submicron sulfuric acid aerosol particles was studied using a laminar flow reactor coupled with a differential mobility analyzer to characterize the aerosol. At 26.3-64.5 wt % H2SO4 concentration, the uptake coefficient (γ) was 0.033 ± 0.004, independent of acid strength and of relative humidity at 8-80%. For an acid strength of 45 wt %, Γ decreased with increasing temperature at 263-298 K. Temperature dependence values of -115 ± 30 kJ/mole and -25.5 ± 8.4 J/mole were determined for the changes in enthalpy and entropy of the uptake process, respectively. The results were consistent with a previous model of N2O5 hydrolysis involving a direct and an acid catalyzed mechanism, with uptake under the experimental conditions limited by mass accommodation.
- Hallquist, Mattias,Stewart, David J.,Baker, Jacob,Cox, R. Anthony
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- Study of the Recombination Reaction NO2 + NO3 + M -> N2O5 + M at High Pressures
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The recombination reaction NO2 + NO3 + M -> N2O5 + M was studied in the pressure range 2-200 atm of the bath gas N2.NO3 radicals were formed by laser flash photolysis of N2O and subsequent addition of O atoms to NO2; NO3 formation and disappearance were monitored by absorption spectroscopy at 662 nm.The recombination reaction was found to be close to its high-pressure limit with a limiting high-pressure rate-constant of (2.2 +/- 0.5) x 1E-12 cm3 molecule-1 s-1.For the reaction NO + NO3 -> 2NO2 a rate constant of (2 +/- 1) x 1E-11 cm3 molecule-1 s-1 was derived.
- Cobos, A. E. Croce de,Hippler, H.,Troe, J.
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- Microwave spectrum, large-amplitude motions, and ab initio calculations for N2O5
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The rotational spectrum of dinitrogen pentoxide (N2O5) has been investigated between 8 to 25 GHz at a rotational temperature of ~2.5 K using a pulsed-molecular-beam Fourier-transform microwave spectrometer. Two weak b-dipole spectra are observed for two internal-rotor states of the molecule, with each spectrum poorly characterized by an asymmetric-rotor Hamiltonian. The observation of only 6-type transitions is consistent with the earlier electron-diffraction results of McClelland et al. [J. Am. Chem. Soc. 105, 3789 (1983)] which give a C2 symmetry molecule with the b inertial axis coincident with the C2 axis. Analysis of the 14N nuclear hyperfine structure demonstrates that the two nitrogen nuclei occupy either structurally equivalent positions or are interchanging inequivalent structural positions via tunneling or internal rotation at a rate larger than ~1 MHz. For the two internal rotor states, rotational levels with Ka + Kc even have IN=0, 2, while levels with Ka + Kc odd have IN= 1, where IN is the resultant nitrogen nuclear spin. This observation establishes that the equilibrium configuration of the molecule has a twofold axis of symmetry. Guided by ab initio and dynamical calculations which show a planar configuration is energetically unfavorable, we assign the spectrum to the symmetric and antisymmetric tunneling states of a C2 symmetry N2O5 with internal rotation tunneling of the two NO2 groups via a geared rotation about their respective C2 axes. Because of the Bose-Einstein statistics of the spin-zero oxygen nuclei, which require that the rotational-vibrational-tunneling wave functions be symmetric for interchange of the O nuclei, only four of the ten vibrational-rotational-tunneling states of the molecule have nonzero statistical weights. Model dynamical calculations suggest that the internal-rotation potential is significantly more isotropic than implied by the electron-diffraction analysis.
- Grabow,Andrews,Fraser,Irikura,Suenram,Lovas,Lafferty,Domenech
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- Atmospheric chemistry of C3-Co cycloalkanecarbaldehydes
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The rate coefficients for the gas phase reaction of NO3 and OH radicals with a series of cycloalkanecarbaldehydes have been measured in purified air at 298 ± 2 K and 760 ± 10 Torr by the relative rate method using a static reactor equipped with long-path Fourier transform infrared (FT-IR) detection. The values obtained for the OH radical reactions (in units of 10-11 cm3 molecule-1 s -1) were the following: cyclopropanecarbaldehyde, 2.13 ± 0. 05; cyclobutanecarbaldehyde, 2.66 ± 0.06; cyclopentanecarbaldehyde, 3.27 ± 0.07; cyclohexanecarbaldehyde, 3.75 ± 0.05. The values obtained for the NO3 radical reactions (in units of 10-14 cm 3 molecule-1 s-1) were the following: cyclopropanecarbaldehyde, 0.61 ± 0.04; cyclobutanecarbaldehyde, 1.99 ± 0.06; cyclopentanecarbaldehyde, 2.55 ± 0.10; cyclohexanecarbaldehyde, 3.19 ± 0.12. Furthermore, the reaction products with OH radicals have been investigated using long-path FT-IR spectroscopy and proton-transfer-reaction mass spectrometry (PTR-MS). The measured carbon balances were in the range 89-97%, and the identified products cover a wide spectrum of compounds including nitroperoxycarbonyl cycloalkanes, cycloketones, cycloalkyl nitrates, multifunctional compounds containing carbonyl, hydroxy, and nitrooxy functional groups, HCOOH, HCHO, CO, and CO2.
- D'Anna, Barbara,Wisthaler, Armin,Andreasen, yvind,Hansel, Armin,Hjorth, Jens,Jensen, Niels R.,Nielsen, Claus J.,Stenstrom, Yngve,Viidanoja, Jyrki
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- An efficient method to synthesize TNAD by the nitration of 1,4,5,8-tetraazabicyclo-[4,4,0]-decane with N2O5 and acidic ionic liquids
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An experimental study was carried out on the direct nitration of 1,4,5,8-tetraaza-bicyclo-[4,4,0]-decane to synthesize 1,4,5,8-tetranitro-1,4,5, 8-tetraazabicyclo-[4,4,0]-decane (TNAD) with N2O5 catalyzed by acidic ionic liquids. Var
- Cao, Xiao-Feng,Li, Bin-Dong,Wang, Min
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- Potassium Hexanitratocobaltate(III)
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Potassium hexanitratocobaltate(III) has been prepared by treating potassium hexafluorocobaltate(III) with dinitrogen pentaoxide at 273 K.Solution properties of the product in water and anhydrous organic solvents are reported.The product has been character
- Khalil, Mutasim I.,Logan, Norman,Harris, Arlo D.
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- Electrochemical behavior of IrxRu1-xO2 oxides as anodic electrocatalyst for electrosynthesis of dinitrogen pentoxide
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The IrxRu1-xO2/Ti electrodes (x = 0-1) were prepared by thermal decomposition of non-aqueous solutions of H 2IrCl6 and RuCl3. The surface morphology and microstructure of the IrxRu1-xO2 coatings were characterized by XRD and SEM. The electrochemical characterization of the surface was carried out in a 0.5 mol L-1 H2SO4 solution. The IrxRu1-xO2 coating with x = 0.5 showed a minimal nanocrystalline particle size and a maximum surface charge (q*). The electrochemical behaviors of the IrxRu 1-xO2 coatings for oxidation of N2O4 were determined by cyclic voltammetry (CV), the open circuit potential (OCP) and Tafel plot in 1.7 mol L-1 N2O4/HNO 3 solutions. The open-circuit potential (Eocp) in N 2O4/HNO3 solution was about 1.18 V and it was almost independent of the surface composition. Cyclic voltammetry showed a broad wave feature at 1.4-1.8 V in the anodic scan, which was attributed to the oxidation of NO2 derived from N2O4 to NO 2+. The redox couple of NO2/NO2 + showed a quasi-reversible behavior and the process was under diffusion control. The electrocatalytic activities of various Ir xRu1-xO2 coatings for oxidation of N 2O4 were evaluated by potentiostatic polarization curves under the quasi-steady state conditions. The Ru0.5Ir 0.5O2 coating showed the lowest Tafel slope, 35.7 mV, in the low current densities, indicating that this coating had the highest electrocatalytic activity. The experiments of electrochemical synthesis of N2O5 from N2O4 in nitric acid also indicated that the Ru0.5Ir0.5O2 coating had the best electrocatalytic performance.
- Wang, Qingfa,Wu, Fangmin,Wang, Nan,Wang, Li,Zhang, Xiangwen
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- Nitration of aromatics with dinitrogen pentoxide in a liquefied 1,1,1,2-tetrafluoroethane medium
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Regardless of the sustainable development path, today, there are highly demanded chemical productions still operating that bear environmental and technological risks inherited from the previous century. The fabrication of nitro compounds, and nitroarenes in particular, is traditionally associated with acidic wastes formed in nitration reactions exploiting mixed acids. However, nitroarenes are indispensable for industrial and military applications. We faced the challenge and developed a greener, safer, and yet effective method for the production of nitroaromatics. The proposed approach comprises the application of an eco-friendly nitrating agent, namely dinitrogen pentoxide (DNP), in the medium of liquefied 1,1,1,2-tetrafluoroethane (TFE) - one of the most non-hazardous Freons. Importantly, the used TFE is not emitted into the atmosphere but is effortlessly recondensed and returned into the process. DNP is obtainedviathe oxidation of dinitrogen tetroxide with ozone. The elaborated method is characterized by high yields of the targeted nitro arenes, mild reaction conditions, and minimal amount of easy-to-utilize wastes.
- Fauziev, Ruslan V.,Kharchenko, Alexandr K.,Kuchurov, Ilya V.,Zharkov, Mikhail N.,Zlotin, Sergei G.
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p. 25841 - 25847
(2021/08/09)
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- Synthesis and mutual transformations of nitronium tetrakis(nitrooxy)- And tetrakis(2,2,2-trifluoroacetoxy)borates
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Nitronium borates of NO2[B(OX)4] type with X = CF3CO and NO2 as ligands were synthesized, and their structures were determined by powder X-ray diffraction. Crystalline NO2[B(ONO2)4] is relatively stable at room temperature and undergoes transformation to B2O3 upon heating. The [B(CF3COO)4]- anion was obtained for the first time and characterized as a structural fragment of a solid compound. The possibility of reversible modification of the complex anion by replacement of the nitrate or trifluoroacetate ligand was demonstrated for the first time by the mutual transformations of NO2[B(ONO2)4] and NO2[B(CF3COO)4].
- Zelenov, Victor P.,Gorshkov, Evgeny Yu.,Zavaruev, Mikhail V.,Dmitrienko, Artem O.,Troyan, Ivan A.,Pivkina, Alla N.,Khakimov, Dmitry V.,Pavlikov, Alexander V.
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p. 13944 - 13951
(2020/09/03)
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- Gas-Phase Oxidation of Allyl Acetate by O3, OH, Cl, and NO3: Reaction Kinetics and Mechanism
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Allyl acetate (AA) is widely used as monomer and intermediate in industrial chemicals synthesis. To evaluate the atmospheric outcome of AA, kinetics and mechanism of its gas-phase reaction with main atmospheric oxidants (O3, OH, Cl, and NO3) have been investigated in a Teflon reactor at 298 ± 3 K. Both absolute and relative rate methods were used to determine the rate constants for AA reactions with the four atmospheric oxidants. The obtained rate constants (in units of cm3 molecule-1 s-1) are (1.8 ± 0.3) × 10-18, (3.1 ± 0.7) × 10-11, (2.5 ± 0.5) × 10-10, and (1.1 ± 0.4) × 10-14, for reactions with O3, OH, Cl, and NO3, respectively. While results for reactions with O3, OH and Cl are in good agreement with previous studies, the kinetics for the reaction with NO3 is reported for the first time in this study. On the basis of determined rate constants, the tropospheric lifetimes of AA are ρO3 = 9 days, ρOH = 5 h, ρCl = 5 days, ρNO3 = 2 days. On the basis of the products study, reaction mechanisms for these oxidations have been proposed and the reaction products were detected using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and Fourier transform infrared spectroscopy (FTIR). Results show that the main products formed in these reactions are carbonyl compounds. In particular, 2-oxoethyl acetate was detected in all four AA oxidation reactions. Compared to previous studies, several new products were determined for reactions with OH and Cl. These results form a set of comprehensive kinetic data for AA reactions with main atmospheric oxidants and provide a better understanding of the degradation and atmospheric outcome of unsaturated acetate esters in the troposphere, during both daytime and nighttime.
- Wang, Shuyan,Du, Lin,Zhu, Jianqiang,Tsona, Narcisse T.,Liu, Shijie,Wang, Yifeng,Ge, Maofa,Wang, Wenxing
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p. 1600 - 1611
(2018/02/22)
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- Nitrosonium nitratometallates NO[M(NO3)3] (M = Co, Ni): new synthetic approach and crystal structures
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Monoclinic and triclinic modifications of nitrosonium nitratonickelate NO[Ni(NO3)3] as well as triclinic modification of nitrosonium nitratocobaltate NO[Co(NO3)3] (isostructural to triclinic NO[Ni(NO3)3]) have been synthesized by a new synthetic approach. Single crystal XRD studies revealed the similarity of all these structures in which octahedrally coordinated metal atoms are connected through NO3? bridges forming three-dimensional distorted cubic framework with NO+ cations located in the framework cavities.
- Deeva, Evgeniya B.,Merkulova, Anna V.,Troyanov, Sergey I.,Zakharov, Maxim A.,Tafeenko, Viktor A.,Kozlovskii, Vadim F.,Morozov, Igor V.
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p. 421 - 422
(2016/10/05)
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- An experimental study of the gas-phase reactions of no3 radicals with a series of unsaturated aldehydes: Trans -2-hexenal, trans -2-heptenal, and trans -2-octenal
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Rate constants for the gas-phase reactions of the NO3 radical with a series of unsaturated aldehydes, trans-2-hexenal, trans-2-heptenal, and trans-2-octenal, have been measured using absolute rate method at 294 ± 3 K and atmospheric pressure. This work was performed to clarify discrepancies found in the literature and thus led to a clearer view of the effect of the increasing carbon chain length on the reactivity of trans-2-alkenals. The rate constants were determined to be (4.7 ± 1.5) × 10-15, (5.3 ± 1.6) × 10-15, and (5.6 ± 2.3) × 10-15 cm3 molecule-1 s-1 for trans-2-hexenal, trans-2-heptenal, and trans-2-octenal, respectively. These results clearly indicate that the carbon chain lengthening of the trans-2-alkenals does not significantly affect the rate constant. In addition, the mechanism for the reaction of NO3 with these unsaturated aldehydes was also investigated. Unsaturated peroxynitrate-type compounds that are exclusively formed through the abstraction channel were observed as the main products.
- Kerdouci, Jamila,Picquet-Varrault, Bénédicte,Durand-Jolibois, Régine,Gaimoz, Cécile,Doussin, Jean-Fran?ois
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p. 10135 - 10142
(2013/01/15)
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- XeOF3-, an example of an AX3YE2 valence shell electron pair repulsion arrangement; Syntheses and structural characterizations of [M][XeOF3] (M = Cs, N(CH3) 4)
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The XeOF3- anion has been synthesized as its Cs + and N(CH3)4+ salts and structurally characterized in the solid state by low-temperature Raman spectroscopy and quantum-chemical calculations. Vibrational frequency assignments for [Cs][XeOF3] and [N(CH3) 4][XeOF3] were aided by 18O enrichment. The calculated anion geometry is based on a square planar AX3YE 2 valence-shell electron-pair repulsion arrangement with the longest Xe-F bond trans to the oxygen atom. The F-Xe-F angle is bent away from the oxygen atom to accommodate the greater spatial requirement of the oxygen double bond domain. The experimental vibrational frequencies and trends in their isotopic shifts are reproduced by the calculated gas-phase frequencies at several levels of theory. The XeOF3- anion of the Cs + salt is fluorine-bridged in the solid state, whereas the anion of the N(CH3)4+ salt has been shown to best approximate the gas-phase anion. Although [Cs][XeOF3] and [N(CH 3)4][XeOF3] are shock-sensitive explosives, the decomposition pathways for the anions have been inferred from their decomposition products at 20°C. The latter consist of XeF2, [Cs][XeO2F3], and [N(CH3)4][F]. Enthalpies and Gibbs free energies of reaction obtained from Born-Fajans-Haber thermochemical cycles support the proposed decomposition pathways and show that both disproportionation to XeF2, [Cs][XeO2F3], and CsF and reduction to XeF2, CsF, and O2 are favorable for [Cs][XeOF3], while only reduction to XeF2 accompanied by [N(CH3)4][F] and O2 formation are favorable for [N(CH3)4][XeOF3]. In all cases, the decomposition pathways are dominated by the lattice enthalpies of the products.
- Brock, David S.,Mercier, Helene P. A.,Schrobilgen, Gary J.
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p. 10935 - 10943
(2010/09/16)
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- Efficient conversion of NO2 into N2 and O2 in N2 or into N2O5 in Air by 172-nm Xe 2 excimer lamp at atmospheric pressure
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Decomposition of NO2 (200 ppm) in N2 or air by 172-nm Xe2 excimer lamp was studied at 1 atm. The NO2 conversion in N2 was 99%, and the formation ratios of N2, O 2, NO, and N2O were 47, 98, 0, and 2%, respectively, after 30 min irradiation. The NO2 in air (5-20% O2) could be completely converted to N2O5 and HNO3 due to reactions by O3 and H2O after only 1.0-1.5 min irradiation. The present results give a new simple photochemical aftertreatment technique of NO2 in air without using any catalysts. Copyright
- Tsuji, Masaharu,Kawahara, Masashi,Senda, Makoto,Noda, Kenji
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p. 376 - 377
(2007/10/03)
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- Products and mechanisms of the reaction of oleic acid with ozone and nitrate radical
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The heterogeneous reactions of deposited, millimeter-sized oleic acid droplets with ozone and nitrate radicals are studied. Attenuated total reflectance infrared spectroscopy (ATR-IR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS) are used for product identification and quantification. The condensed-phase products of the ozonolysis of oleic acid droplets are 1-nonanal (30 ± 3% carbon yield), 9-oxononanoic acid (14 ± 2%), nonanoic acid (7 ± 1%), octanoic acid (1 ± 0.2%), azelaic acid (6 ± 3%), and unidentified products. The infrared spectra show that a major fraction of the unidentified products contain an ester group. Additionally, the mass spectra show that at least some of the unidentified products have molecular weights greater than 1000 amu, which implicates a polymerization reaction. The observed steps of 172 amu (9-oxononanoic acid) and 188 amu (azelaic acid Criegee intermediate) in the mass spectra suggest that these species are the monomers in the condensed-phase polymerization reactions. 9-Oxononanoic acid is proposed to lengthen the molecular chain via secondary ozonide formation; the azelaic acid Criegee intermediate links molecules units via ester formation (specifically, α-acyloxyalkyl hydroperoxides). For the reaction of oleic acid with nitrate radicals, functional groups including -ONO2, -O 2NO2, and -NO2 are observed in the infrared spectra, and high molecular weight molecules are formed. Environmental scanning electron microscopy (ESEM) is employed to examine the hygroscopic properties of the oleic acid droplets before and after exposure to ozone or nitrate radical. After reaction, the droplets take up water at lower relative humidities compared to the unreacted droplets. The increased hygroscopic response may indicate that the oxidative aging of atmospheric organic aerosol particles has significant impact on radiative forcing. $ 2005 American Chemical Society.
- Hung, Hui-Ming,Katrib, Yasmine,Martin, Scot T.
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p. 4517 - 4530
(2008/10/09)
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- Methods for preparing standard nitrate radical (NO3) gas to calibrate the LIF-based instrument for measurements in the atmosphere
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Preparation of standard NO3 gas is explored at the level of ppbv for atmospheric measurements utilizing an LIF instrument. The sequence of thermal decomposition of N2O5 and gas phase titration of NO3 by adding NO is useful. To reduce NO2 contamination in N2O5, N2O5 trapping after mixing NOx and O3 was adopted. As a convenient method in the field studies, dynamic mixing of NOx and O3 was explored. Copyright
- Matsumoto, Jun,Imai, Hidekazu,Kosugi, Naohiro,Kajii, Yoshizumi
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p. 1214 - 1215
(2007/10/03)
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- Trisubstituted carbocyclic cyclophilin binding compounds and their use
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The present invention relates to novel, non-peptidic small organic compounds having an affinity for cyclophilin (CyP)-type immunophilin proteins, and to pharmaceutical compositions comprising one or more of the said compounds. The invention further relates to the uses of these compounds and compositions for binding CyP-type proteins, inhibiting their peptidyl-prolyl isomerase activity, and for research, development, and therapeutic applications in a variety of medical disorders.
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- Second Harmonic Generation Studies of Ozone Depletion Reactions on Ice Surfaces under Stratospheric Conditions
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Hypochlorous acid, HOCl, an important species in the proposed heterogeneous mechanism for stratospheric ozone depletion, has been observed directly at submonolayer amounts on a single crystalline basal ice surface at 155-188 K, using the nonlinear optical method second harmonic generation. The ice is held in equilibrium with its vapor pressure. Second harmonic generation signals from 290 to 310 nm spectroscopically characterize the species and enable us to follow isothermal desorption kinetics in situ. HOCl desorbs as a single species with a ??G*des = 48 ?± 4 kJ/mol, close to the cohesive energy of ice itself. The lifetime of HOCl on the clean ice surface at 185 K is estimated to be 4 s and the equilibrium surface coverage at 10-11 Torr HOCl to be around 4 ?? 1011 molecules/cm2, corresponding to about 0.1% of a monolayer. However, these same measurements performed on ice predosed with varying amounts of HNO3 show that the HOCl lifetime is lengthened by coadsorbed HNO3, depending on the HNO3 surface density.
- Geiger, Franz M.,Tridico, Anthony C.,Hicks, Janice M.
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p. 8205 - 8215
(2007/10/03)
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- Reaction probabilities for N2O5 hydrolysis on sulfuric acid and ammonium sulfate aerosols at room temperature
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The uptake coefficients for N2O5 hydrolysis have been measured at room temperature on micron-sized aerosols composed of both sulfuric acid aqueous solutions and ammonium sulfate solutions. The measurements have been performed in a laminar flow tube which is coupled to a chemical ionization mass spectrometer for monitoring the concentration of N2O5 in the gas phase and an optical particle counter which sizes the aerosols and determines their number density. The aerosols are generated with an ultrasonic nebulizer from aqueous solutions of either sulfuric acid or ammonium sulfate, and their liquid-phase concentration is determined by the relative humidity (RH) set within the flow tube. For both the sulfuric acid and ammonium sulfate aerosols, the reaction probability (γ) is largest for the lowest relative humidities studied: for sulfuric acid aerosols, γ = 0.05-0.06 for RH = 9-20%, γ = 0.02 for RH = 90%; for ammonium sulfate aerosols, γ = 0.04-0.05 for RH = 50-69%, γ = 0.02 for RH = 83-94%. In the case of ammonium sulfate aerosols, significant reactivity with N2O5 is found at relative humidities below the deliquescence point of 80%, consistent with the observation that ammonium sulfate aerosols are readily formed in supersaturated, liquid states.
- Hu,Abbatt
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p. 871 - 878
(2007/10/03)
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- Crystal structure and raman spectrum of nitroniumtrinitrosylpentanitratozirconate, NO2(NO)3[Zr(NO3)5]4
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Single crystals of the triclinic compound NO2(NO)3[Zr(NO3)5]4 (a = 1376.3(6), b = 1376.9(11), c = 1632.0(7) pm, α = 114.63°(5), β = 114.90°(4), γ = 90.34°(5); P1, Z = 2) have been investigated by x-ray diffraction and Raman spectroscopy. The crystals were prepared by reaction of N2O5 with ZrCl4. The product was sublimed and crystallised in nitroethane.
- Kaiser,Ebinal,Menzel,Stumpp
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p. 449 - 455
(2008/10/09)
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- Rate Coefficients for the Thermal Decomposition of BrONO2 and the Heat of Formation of BrONO2
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Rate coefficients (k-7) for the thermal decomposition of bromine nitrate, BrONO2 + M -> BrO + NO2 + M, have been obtained at temperatures between 320 and 340 K and pressures between 100 and 1000 Torr.These data are combined with recommended values for the reverse reaction to obtain an equilibrium constant for the reaction pair, KP,7 = 5.44E-9 exp(14192/T) atm-1, and a heat of reaction for the thermal dissociation of 28.2 +/- 1.5 kcal/mol at 298 K.This reaction enthalpy is used in conjunction with literature data to arrive at a consistent set of ΔH0f(298 K) data for BrONO2 (10.1 +/- 2.0 kcal/mol), BrO (30.4 +/- 2.0 kcal/mol), HOBr (-14.1 +/- 2.0 kcal/mol), and Br2O (27.3 +/- 2.0 kcal/mol).Additional measurements were made to determine the rate coefficient for Br atom reaction with BrONO2 (k11) relative to the rate coefficient for its reaction with CH3CHO (k12) at 298 K: k11/k12 = 12.5 +/- 0.6.This relative rate measurement yields a rate coefficient of (4.9 +/- 1.5)E-11 cm3 molecule-1 s-1 for k11, using the currently recommended value for k12.Approximate rate constant for reaction of NO (reaction 17) and BrNO (reaction 19) with BrONO2 were also obtained: k17 = 3E-19 cm3 molecule-1 s-1, k19 > 1E-16 cm3 molecule-1 s-1.
- Orlando, John J.,Tyndall, Geoffrey S.
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p. 19398 - 19405
(2007/10/03)
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- Photochemical Decay Reactions of N2O5, HNO3, ClNO3 and BrNO3 in the Energy Range 10-20 eV.
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The photochemical behaviour of gaseous N2O5, HNO3, ClNO3 and BrNO3 has been investigated in the energy range 10-20 eV by photoionization mass spectrometry using monochromatized synchrotron radiation.The decay reactions are analyzed using the photoion yield curves of fragment ions and their appearance energies.Hitherto unknown photochemical reactions and thermochemical data have been evaluated. Keyword Mass Spectrometry / Photochemistry / Photoionization, Dissoziative / Spectroscopy, VUV
- Jochims, H.-W.,Denzer, W.,Baumgaertel, H.,Loesking, O.,Willner, H.
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p. 573 - 578
(2007/10/02)
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- Pulse Radiolysis Study of Aqueous Nitric Acid Solutions. Formation Mechanism, Yield, and Reactivity of NO3 Radical
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A pulse radiolysis study of aqueous nitric acid and nitrate solutions has been carried out.The formation kinetics of NO3 radical was followed with nanosecond time resolution.Two formation processes of NO3 in nitric acid solutions were directly demonstrated: a fast one completed during the electron pulse and a slow one occuring in a microsecond time range.In nitrate solutions, only the fast formation process was observed.The slow formation process in nitric acid solutions was confirmed to be the reaction of OH radicals with undissociated nitric acid molecules, OH + HNO3 -> H2O + NO3, with a rate constant of (1.4 +/- 0.1) x 108 M-1 s-1.The fast formation process is most probably the direct action of radiation on nitrate anion or nitric acid: NO3- e- + NO3 or HNO3 HNO3+ + e- -> NO3 + H+ + e-.The molar absorption coefficient of NO3 was evaluated as 1300 +/- 100 M-1 cm-1 at 640 nm.On the basis of this result, G values of NO3 were evaluated in nitric acid, lithium nitrate, and sodium nitrate solutions.The main decay reaction of NO3 was proposed to be NO3 + NO2 -> N2O5 in nitric acid solutions and its rate constant was evaluated as (1.7 +/- 0.3) x 109 M-1 s-1.Rate constants of reactions of NO3 with radiolytic products and some other compounds were obtained.
- Katsumura, Y.,Jiang, P. Y.,Nagaishi, R.,Oishi, T.,Ishigure, K.,Yoshida, Y.
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p. 4435 - 4439
(2007/10/02)
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- The barrier discharge in dielectrics with a high dielectric constant. II. Synthesis of ozone
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We have studied the properties of the barrier discharge and of the synthesis of ozone for changes in the dielectric constant ε from a few units to several thousand.
- Gibalov, V. I.,Volodin, V. E.,Samoilovich, V. G.
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p. 1541 - 1543
(2007/10/02)
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