Excess NO Research Articles

Formation and Thermal Decomposition of Butyl-Substituted Peroxyacyl Nitrates: n-C4H9C(O)OONO2 and i-C4H9C(O)OONO2

The butyl-substituted peroxyacyl nitrates n-C 4 H 9 C(O)-OONO 2 and i-C 4 H 9 C(O)OONO 2 have been synthesized in the liquid phase, prepared in-situ in the gas phase by sunlight irradiation of aldehyde-NO mixtures, measured by electron capture gas chromatography, and characterized in a number of gas-phase and liquid-phase tests. Gas-phase yields as a fraction of initial NO were 0.39 for the n-butyl isomer and 0.20 for the isobutyl isomer. The corresponding gas-phase aldehyde oxidation mechanisms are outlined. Thermal decomposition in the presence of excess NO yielded n-butanal and isobutanal as the major carbonyl products.(...)

Reductive Disproportionation of NO Mediated by Copper Complexes: Modeling N2O Generation by Copper Proteins and Heterogeneous Catalysts

Nitrito‐O,O‐copper complexes and dinitrogen oxide are the products of the reaction of excess NO with the nitrosyl complexes [LCu(NO)] (L = substituted tris(pyrazolyl)hydroborate), a process that models environmentally important transformations carried out by copper ions in proteins and zeolites. According to the results of kinetic studies, the involvement of dimeric copper species in the rate‐determining step is ruled out, which suggests that NO coupling occurs at a single metal ion.

Nitrogen fertilization strategies in a short-rotation sycamore plantation

This study evaluates the effect of different nitrogen fertilization regimes in an American sycamore ( Platanus occidentalis L.) plantation on tree growth, fertilizer recovery by the trees, and nitrate leaching from the soil with the objective of determining the optimum application regime. A total of 450 kg N ha −1 was added as urea over a 3 year period at the following rates: a single dose shortly after planting (O1); 150 kg N ha −1 applied once every year (AE); applications of 50 kg N ha −1 three times per year (P); annual doses that increased with tree growth (AB: 50, 150, and 250 kg N ha −1). Aboveground biomass production, N accumulation in biomass, and soil solution chemistry were measured between 1989 and 1992 in three replicate plots per treatment and compared with those in unfertilized control plots. The O1 fertilization was inefficient because growth benefits were short-lived and were associated with excessive NO 3 leaching losses in the first year. Multiple fertilizer applications generally resulted in better growth, while soil solution NO 3 levels depended on the actual rate and frequency of fertilization. Nitrate leaching was greatest in the AE plots. The AB treatment, in which annual N additions increased commensurate with tree size, was optimum in terms of enhancing stem biomass production and reducing potential groundwater contamination. The reduction in fertilizer use efficiency and the increase in NO 3 leaching in the third year indicate that the input of 250 kg N ha −1 exceeded tree N retention capacity and should have been reduced to approximately one-half that rate. Increasing the frequency of fertilization from once per year to three times per growing season also decreased NO 3 leaching losses (i.e. improved N recovery) without measurable benefits to biomass production, and may therefore not be cost-effective in commercial operations.

Protection against light-induced retinal degeneration by an inhibitor of NO synthase.

The existence of nitric oxide synthase (NOS) in retinal rod outer segments and pigmented epithelial cells suggests that NO in excess could impair the interaction between these cells, resulting in photoreceptor degeneration. To test this hypothesis, NG-nitro-L-arginine methyl ester (L-NAME), an NOS inhibitor, was intraperitoneally injected daily into rats subjected to constant illumination for 7 days in order to destroy their photoreceptors. By measuring photoreceptor nuclear layer thicknesses, we found that L-NAME partially protects (by up to 35%) against the degeneration of photoreceptors and acts to maintain their organization. Thus NO may be involved in the process by which photoreceptor degeneration results from constant illumination of the retina.

Long-path Fourier-transform infrared spectroscopic study of the reactions of trifluoromethylperoxy and trifluoromethoxy radicals with nitrogen dioxide

Mechanisms of the reactions of CF 3 OO and CF 3 O radicals with NO 2 have been studied using the long path FTIR method in the visible (λ≥400 nm) photolysis of CF 3 NO in the presence of excess NO 2 (in mTorr range) in 700 Torr of air at 297±2 K. In the early stage of the photolysis, the predominant F-containing product detected was CF 3 OONO 2 formed via the addition reaction CF 3 OO+NO 2 (+M)↔CF 3 OONO 2 (+M)

Hydrologic and Land‐Use Factors Associated with Herbicides and Nitrate in Near‐Surface Aquifers

AbstractSelected herbicides, atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) metabolites, and NO−3 were examined in near‐surface unconsolidated and bedrock aquifers in the midcontinental USA to study the hydrogeologic, spatial, and seasonal distribution of these contaminants. Groundwater samples were collected from 303 wells during the spring and late summer of 1991. At least one herbicide or atrazine metabolite was detected in 24% of the samples collected for herbicide analysis (reporting limit 0.05 µg/L). No herbicide concentration exceeded the USEPA's maximum contaminant level (MCL) or health advisory level. The most frequently detected compound was the at razine metabolite deethylatrazine [2‐amino‐4‐chloro‐6‐(isopropylamino)‐s‐triazine] followed by atrazine, deisopropylatrazine [2‐amino‐4‐chloro‐6‐(ethylamino)‐s‐triazine], prometon (2,4‐bis(isopropylamino)‐6‐methyoxy‐s‐triazine), metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1methylethyl)acetamide], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide], metribuzin [4‐amino‐6‐(tert‐butyl)‐3‐methylthio‐as‐triazine‐5(4H)‐one], simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine], and cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl]amino]‐2‐methylpropionitrile]. Nitrite plus nitrate, as nitrogen (N), exceeding 3.0 mg/L (excess NO−3), was found in 29% of the samples, and 6% had −3 exceeding the MCL of 10 mg/L. Ammonium as N was detected in excess of 0.01 mg/L in 78% of the samples. A nonlinear increase in the frequency of atrazine detection occurred with decreases in reporting limit. The frequency of atrazine residue detection (atrazine + deethylatrazine + deisopropylatrazine) was 25% greater than for atrazine alone. Herbicide detections and excess NO−3 were notably lacking in the eastern part of the study region where it was estimated that herbicide and fertilizer use were among the largest in the region. Prometon, the second most frequently detected herbicide, was associated with non‐agricultural land use. Herbicide and excess NO−3 were more frequent in unconsolidated aquifers than in bedrock aquifers. Aquifer depth, as direct measurement of proximity to recharge sources, was inversely related to frequency of herbicide detection and excess NO−3.

Lanthanide‐nitrate interaction in anhydrous acetonitrile and coordination numbers of the lanthanide ions: FT‒IR study

AbstractThe interaction between lanthanide ions LnIII (Ln = La, Nd, Sm–Dy, Er, Yb) and nitrate ions is investigated by FT‐IR spectroscopy in dilute anhydrous MeCN solution. The work is performed for ratios R = [NO]t/[LnIII]t ranging from 0 to 8 and for solutions generally 0.05M in LnIII, prepared from anhydrous lanthanide perchlorates Ln(ClO4)3. When nitrate is progressively added to the Ln(ClO4)3 solutions, the formation of [Ln(NO3)n](3−n)+ species is clearly evidenced by the FT‐IR spectra. All the NO3− ions are coordinated and bidentate. A quantitative study was performed using the v1 and v6 vibrational modes for coordinated NO ions. The average coordination numbers estimated for Nd, Eu, Tb, and Er in solutions of trinitrates are 9.0, 9.1, 8.3 and 8.2, respectively (±0.3 unit). In presence of an excess NO, these numbers become 9.8, 10.2, 10.0, 9.8, 9.9, and 9.9 (±0.3 unit) for La, Nd, Eu, Tb, Er, and Yb, respectively. No hexanitrato species forms under the experimental conditions used (R up to 8). The structural aspect of the various nitrato species is also investigated. In the pentanitrato species, all the ligands appear to be equivalent, while large inequivalences are observed for Ln(NO3)3 solutions. Since for the latter most of the absorption bands assigned to nitrate vibrations contain several components, a curve‐fitting procedure has been used for decomposing the v2, v4 and v6 vibrations. There is a considerable difference between LnIII ions, the nitrate inequivalences being larger in the middle of the series.

Autoxidation of NO in aqueous solution

AbstractThe reaction of NO with O2 has been investigated in aqueous solution. As demonstrated by ion chromatography, the sole product is NO2−. Kinetic studies of the reaction by stopped‐flow methods with absorbance and conductivity detection are in agreement that the rate law is ‐d[O2]/dt=k[NO]2[O2] with k = 2.1 × 106 M−2 s−1 at 25°C. This rate law is unaffected by pH over the range from pH 1 to 13, and it holds with either NO or O2 in excess. By studying the reaction over the temperature range from 10 to 40°C, the following activation parameters were obtained: ΔH≠ = 4.6 ± 2.1 kJ mol−1 and ΔS≠=−96 plusmn; 4 J K−1 mol−1. © 1993 John Wiley & Sons, Inc.

External magnetic field effects on chemiluminescence intensities from C 2(d) and CN(B) states in low pressure C 2H 2/N, O flames

Magnetic field effects on chemiluminescence intensities from some reaction intermediates in low pressures C 2H 2/N, O flames were measured. O atoms were produced without O 2 by adding NO into a discharged N 2 stream. Diffusion flames were formed between electromagnet poles when a C 2H 2 stream from another inlet encountered an N 2 stream containing O and/or N atoms. Both partial titration by and excess addition of NO enhanced the magnetic field quenching of the chemiluminescence due to the C 2 Swan system. The CN violet showed magnetic field quenching only when the excess NO was present. Possible mechanisms for these magnetic field effects are discussed briefly.

Infrared flash kinetic spectroscopy of the ketenyl radical

The high resolution infrared spectrum of the heavy atom antisymmetric stretch of the ketenyl radical (HCCO) has been observed by means of infrared kinetic spectroscopy producing the ketenyl by 193 nm photolysis of ketene with diode laser probing of the transient absorption. Individual rovibrational transitions have been identified near the band origin located at approximately 2023 cm −1. A preliminary kinetic study of the ketenyl radical's reaction with nitric oxide was conducted. A second order rate constant of 3.9(5) × 10 −11 cm 3 molecule −1 s −1 was obtained for this reaction by following the decay of ketenyl in the presence of excess NO.

T-Butylimido and t-butylimido oxo aryls of rhenium. X-ray crystal structures of Re(NBu t) 2(2,6-Me 2C 6H 3) 2, Re(NBu t)(2,4,6-Me 3C 6H 2)(C 27H 32), Re(NBu t) 3(2,4,6-Me 3C 6H 2), [(Bu tN)Br(2,4,6-Me 3C 6H 2)Re(μ-NBu t)(μ-O) [formula omitted](OC 6H 2Me 2CH 2)(NBu t)], [Re(NBu t)(O)Ar(μ-O)] 2, Ar = 2,6-C 6H 3 and 2,4,6-C 6H 2

The interaction of Re(NBu t ) 2Cl 3 with 2,6-xylyl magnesium bromide gives rise to the paramagnetic rhenium(VI) compound, Re(NBu t ) 2(xyl) 2, which is readily oxidized to the cation [Re(NBu t ) 2(xyl) 2] +, isolated as its PF 6 − salt; the latter with Bu t NC gives the iminoacyl cation [Re(NBu t ) 2(xyl)(Bu t NCxyl)] +. An unstable rhenium(V) anion, [Re(NBu t ) 2(xyl) 2] −, has been characterized. Interaction of Re(NBu t ) 2Cl 3 with excess mesityl Grignard gives a compound of stoichiometry Re(NBu t )(mes)(C 27H 32) in which three aromatic rings are coupled, the central one comprising a η 5-cyclohexadienyl ring bearing an exo-mesityl group in the 1-position and in the 3-position linked by a CH 2 group to an aryl group σ-bonded to the metal, which is formally in the V oxidation state. The compound Re(NBu t ) 2Cl( o-tol) 2 has been synthesized; treatment with AgPF 6 produces the salt [Re(NBu t ) 2( o-tol) 2]PF 6. Hydrolysis of Re(NBu t ) 2ReCl 3 with LiOH gives Re(NBu t ) 2 Cl(OH) 2, which on arylation, gives the oxo imido species Re(NBu t ) 2(O)mes and [(Bu t N)Br(mes)Re(μ-NBu t )(μ-O)Re(OC 6H 2Me 2CH 2)(NBu t ) 2]. Interaction of excess NO with Re(NBu t ) 2Ar 2, Ar = 2,6-xylyl and mesityl, gives the compounds [Re(NBu t )(O) (μ-O)Ar] 2; the reaction involves a unique NN bond formation to give Bu t NNAr. Stoichiometric reactions of Re(NBu t ) 2(xyl) 2 and NO lead to the complexes Re(NBu t )2 (xyl) 2NO and Re(NBu t ) 2(O)(xyl). Mechanisms for the NO reactions are proposed. X-ray structures of the compounds listed in the title have been determined; the compounds [Re (NBu t )(O)(μ-O)Ar] 2 have asymmetric oxo bridges.

Studies with nitryl hypochlorite: thermal dissociation rate and catalytic conversion to nitric oxide using an NO/O3 chemiluminescence detector

A NO/O 3 chemiluminescence detector equipped with a gold catalyst is adapted to provide a measure of the thermal decomposition rate of ClONO 2 in an Ni 2 /O 2 gas mixture and, in a related way, provide the absolute concentration of ClONO 2 in a flowing gas stream. The approach is to add ClONO 2 , in the parts per million by volume range, to the flow stream of the detector in the presence of excess NO. As the sample is heated, ClONO 2 is thermally dissociated and the subsequent scavenging reaction of ClO with NO produces Cl and NO 2 . Cl goes on to react with ClONO 2 to form NO 3 which, in turn, reacts with NO to produce NO 2 . The loss of NO from the flow is precisely monitored downstream in the detector by the change in the chemiluminescence produced in the reaction of NO with reagent O 3

Mechanism of the reaction NH( 1Δ)+NO→N 2O+H in the gas phase

Hydrazoic acid HN 3, was photolyzed in the presence of a controlled amount of NO in the gas phase, to investigate the reaction of NH ( 1Δ) with NO. Ab initio CI studies indicate that the ultimate product should be N 2O, which would arise via an intermediacy of the adduct radical HNNO ( 2A′). Mass-spectrometric analyses of the reaction mixtures have shown that N 2O is indeed a principal product but that a sizable quantity of H 2O has been formed concurrently. Quantum yields of N 2O are found to increase in proportion to the initial molar fractions of NO in the reactant gas mixtures used. It is concluded that NH ( 1Δ) enters into capture (no-barrier) reactions with NO and HN 3 in a competitive manner, to give N 2O and NH 2, respectively, the latter product eventually leading to H 2O through a rapid capture reaction with excess NO.

An FT-i.r. study of the deposition of Co(CO) 3NO on zeolite-Y: influence of the support on the formation of isocyanates

Fourier transform i.r. spectroscopy has been used to study the adsorption and subsequent reactions of Co(CO) 3NO on a sodium zeolite-Y (NAY) and the results have been compared with those obtained previously for deposition on Al 2O 3. The support strongly influences the nature of the evolution of this reaction; whereas isocyanates form easily at room temperature on Al 2O 3, this does not occur on NaY but N 2 is generated instead. However, with both supports, oxidation of the metallic centre occurs with the generation of a dinitrosyl species having a pair of NO bands near 1880 and 1800 cm -1. For both supports, this oxidation is inhibited if the coadsorption is carried out in the presence of excess CO, and it is accelerated during coadsorption with excess NO. It is suggested that the Lewis acid Al(+III) sites on Al 2O 3 play a pivotal role in the generation of surface nitride leading to isocyanate formation.

Surface-catalyzed formation of electronically excited nitrogen dioxide and oxygen

The surface-catalyzed recombination of NO and O atoms to produce excited NO/sub 2/ molecules has been studied. By using the reaction of N atoms with NO (N + NO ..-->.. N/sub 2/ + O), the O atoms were produced in the absence of molecular oxygen. The resultant orange glow attributed to the electrically excited NO/sub 2/ molecules was observed directly over a nickel metal catalyst in a flow system operated in the 20 mtorr range. Measurements of the attenuation of the intensity as a function of distance from the catalyst yielded an observed effective lifetime of approximately 79 ..mu..s, which is in the range of radiative lifetimes of NO/sub 2/. The Herzberg emission from the O/sub 2/ (A/sup 3/ ..sigma../sub u//sup +/) state was observed as a function of distance from the catalyst surface. With increasing O-atom concentration the observed effective lifetime appears to increase. When the reaction of NO with N atoms was used to produce O atoms at the equivalence point, i.e., with no excess NO and N atoms, no Herzberg emission was observed. 39 references, 7 figures.

Kinetic measurements on the system No + No2 ⇌ N2O3 by time-resolved infrared laser absorption

The first direct kinetic measurements have been made on the reaction NO + NO2 ⇌ N2O3. Equilibrium mixtures of the nitrogen oxides containing excess NO at 208 ± 3 K were perturbed by flash photolysis of a fraction of the N2O3. The rate of relaxation to equilibrium was monitored by observing the transmittance of a line from a cw CO laser selected to coincide with the v band in N2O3. At pressures up to 1000 Torr (M = He, Ar) the association reaction is third-order with k0(M = He) = (3.6 ± 0.15) × 10−33 cm6 molecule−2 s−1 and k0(M = Ar) = (5.5 ± 0.8) × 10−33 cm6 molecule−2 s−1.

Atmospheric reactions of styrenes and peroxybenzoyl nitrate

Reaction products and oxidation pathways were investigated for a number of organics relevant to the atmospheric persistence of styrenes and of peroxybenzoyl nitrate (PBzN). Systems studied included: (a) PBzN formation from benzaldehyde-NO 2, benzaldehyde-Cl 2NO 2, toluene-NO, styrene-NO, and trans-β-methylstyrene-NO in sunlight; (b) thermal decomposition of PBzN vs. peroxyacetyl nitrate (PAN) in the presence of excess NO in the dark, with PAN-PBzN mixtures prepared from Cl 2NO 2-benzaldehyde-acetaldehyde or from trans-β-methylstyrene-NO in sunlight; and (c) rates and products of the dark reaction between the styrenes and ozone. Reaction products, including o-nitrophenol from PBzN + NO, carbonyls and carboxylic acids from styrene + O 3, and carbonyls, PAN and PBzN from organic-NO x , are discussed in terms of ozone and OH-initiated reaction mechanisms. The atmospheric removal of styrenes and their possible importance as PBzN precursors are briefly examined.

Kinetics of the reaction Cl + NO2 + M

AbstractThe termolecular rate constant for the reaction Cl + NO2 + M has been measured over the temperature range 264 to 417 K and at pressure 1 to 7 torr in a discharge flow system using atomic chlorine resonance fluorescence at 140 nm to monitor the decay of Cl in an excess of NO2. The results are\documentclass{article}\pagestyle{empty}\begin{document}$k_1^{{\rm He}} = 9.4{\rm } \times {\rm }10^{ - 31} \left({\frac{T}{{300}}} \right)^{ - 2.0 \pm 0.05} {\rm cm}^6 {\rm s}^{ - {\rm 1}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$k_1^{{\rm N}2} = (14.8{\rm } \pm {\rm }1.4){\rm } \times {\rm 10}^{ - 31} {\rm cm}^6 {\rm s}^{ - 1}$\end{document} at 296 K where error limits represent one standard deviation. The systematic error of k1 measurements is estimated to be about 15%. Using a static photolysis system coupled with the FTIR spectrophotometer the branching ratio for the formation of the two possible isomers was found to be ClONO(⩾75%) and CINO2(⩽25%) in good agreement with previous measurements.

The cooperativity of nitric oxide hemoglobin ligand exchange in single crystals as studied by EPR

Single crystals of human oxyhemoglobin are exposed to aqueous solutions of nitric oxide at pH 6.7 and 6 °C. The EPR spectrum of crystals at 85–100 K selected after various times of exposure to NO are recorded. The intensities of the alpha and beta subunits are determined from the c axis spectrum of the crystal. With NO in stoichiometric excess, crystals sampled early (3–200 min) display the EPR of molecules with NO bound to an average of two alpha and one beta subunit. The NO diffuses into the crystals with a diffusion rate constant of 1.5×10−9 cm2 s−1.The NO binds to the last beta subunit at a rate of 5.1×10−6 s−1.

A numerical response of the middle atmosphere to the 11-year solar cycle

A two-dimensional numerical model with coupled photochemistry and dynamics has been used to investigate the response of the middle atmosphere (16–116 km) to changes in solar activity over the 11-year solar cycle. Model inputs that vary with solar cycle include solar radiation, cosmic ray and auroral ionization rates and the flux of NO x at the model's upper boundary. In this study, the results of model runs for solar cycle minimum and maximum conditions are compared. In the stratosphere, using currently accepted estimates of changes in solar radiation at wavelengths longer than 180 nm, only small responses in ozone, temperature and zonal winds are obtained. On the other hand, changes at shorter wavelengths, and the effects of particle precipitation, lead to large variations in the abundances of trace species in the thermosphere and upper mesosphere. In particular, very large abundances of NO x are produced above 90 km by auroral particle precipitation. Considerable amounts of NO x are transported subsequently to the stratosphere by the global mean meridional circulation. It is shown that this excess NO x can lead to significant decreases in ozone concentrations at high latitudes and that it may explain observations of nitrate deposition in Antarctic snow.