10102-44-0Relevant articles and documents
Product branching ratio of the HCCO + NO reaction
Rim, Kwang Taeg,Hershberger, John F.
, p. 293 - 296 (2000)
Excimer laser photolysis of ketene precursor molocules followed by IR absorption spectroscopy were performed to study the reaction of ketenyl radical (HCCO) radicals with NO at room temperature. CO and CO2 were produced. Considering possible secondary chemistry, CO + (HCNO) was the main product channel, with a branching ratio of 0.88 ± 0.04:1 at 296 K. CO2 + (HCN) was a minor channel, with a branching ratio of 0.12 ±0.04:1. The relative quantum yield for HCCO production in the 193 nm photolysis of CH2CO was estimated to be 0.17 ± 0.02.
IR spectroscopic study of NOx adsorption and NOx-O2 coadsorption on Co2+/SiO2 catalysts
Djonev, Boyan,Tsyntsarski, Boyko,Klissurski, Dimitar,Hadjiivanov, Konstantin
, p. 4055 - 4063 (1997)
Adsorption of nitrogen oxides (NO, NO2) and their coadsorption with oxygen on Co2+/SiO2 samples has been investigated by IR spectroscopy with a view to elucidating the mechanism of selective catalytic reduction (SCR) of NOx with hydrocarbons. A Co2+/SiO2 sample synthesized by ion exchange is characterized by a highly dispersed cobalt and a very weak surface acidity: CO is adsorbed only at low temperature (100 K) forming Co2+ - CO carbonyls [v(CO) = 2180 cm-1]. Adsorption of NO on Co2+/SiO2 leads to the formation of Co2+(NO)2 dinitrosyl complexes (1872 and 1804 cm-1) which are decomposed upon evacuation. Adsorption of NO2, as well as coadsorption of NO and O2, produce NO2 species weakly bound to the support (a band at 1681 cm-1) and N2O4 (a band at 1744 cm-1 with a shoulder at 1710 cm-1), the latter being adsorbed reversibly on both the support and the Co2+ ions. In the second case N2O4 is transformed into surface monodentate nitrates of Co2+ (a band at 1550-1526 cm-1) and partly into bridged nitrates (a band at ca. 1640 cm-1). The monodentate nitrates are stable with respect to evacuation up to 125°C and act as strong oxidising agents: they are reduced by NO, even at room temperature, and by methane at 100°C. In the latter case, organic nitro-compounds and isocyanate groups are registered as reaction products (probably intermediate compounds in SCR). The surface species obtained after NO and NO2 adsorption on Co2+/SiO2 prepared from cobalt acetate (active SCR catalyst) are essentially the same as those observed with the ion-exchanged sample. No monodentate nitrates, however, are formed during NO2 adsorption on a Co2+/SiO2 sample synthesized by impregnation with cobalt nitrate, which accounts for the lack of activity of this sample in the SCR.
14N/15N kinetic isotope effect in the association reaction O(3P)+NO+Ar→NO2+Ar
Umemoto, Hironobu,Tanaka, Kunikazu,Oguro, Shigeki,Ozeki, Ryoji,Ueda, Masashi
, p. 44 - 50 (2001)
The termolecular rate constants for the O(3P)+14NO+Ar→14NO2+Ar and O(3P)+15NO+Ar→15NO2+Ar reactions were determined under room temperature bulk conditions. O(3P) was produced by the pulsed photodissociation of SO2 at 210.4 nm and was monitored by two-photon laser-induced fluorescence at 225.7 nm. The rate constants for 14NO and 15NO were determined to be 5.4±0.2 and 6.1±0.3×10-32cm6s-1, respectively. The error limits are twice the standard errors (S.E.). This isotope effect is opposite to that expected from a statistical model but is similar to that observed in the O3 formation reactions from O(3P) and O2.
Use of a Stopped-flow Technique to measure the Rate Constants at Room Temperature for Reactions between the Nitrate Radical and Various Organic Species
Boyd, Andrew A.,Canosa-Mas, Carlos E.,King, A. Douglas,Wayne, Richard P.,Wilson, Mark R.
, p. 2913 - 2919 (1991)
A stopped-flow apparatus, in which NO3 was detected by optical absorption at λ = 662 nm, has been used to measure overall rate constants at room temperature for reaction of NO3 in systems involving ethene, simple alkanes and chlorinated methanes.Modelling of the reaction with ethene led to a rate constant for the primary step of (1.7 +/- 0.5) * 10 -16 cm3 molecule -1 s-1.However, for H-atom abstraction by NO3 from the saturated organic species, the extensive and largely unquantified secondary chemistry occuring over reaction times of 5 - 20 s meant that only upper limits for the primary rate constants could be accurately assessed (the stoicheiometric factor being assumed to be two or more).The values thus obtained at room temperature were (in units of 10-17 cm3 molecule -1 s-1) 2.7 +/- 0.2, 4.8 +/- 1.7, 60 +/- 10, 0.85 +/- 0.25, 0.48 +/- 0.10 and 6.0 +/- 0.5 for ethane, propane, isobutane (2-methylpropane), acetone, dichloromethane and chloroform.For the reactions of NO3 with ethane and propane, modelling of the kinetics led to estimates of lower limit of the primary rate constants of ethane and propane, modelling of the kinetics led to estimates of lower limits of the primary rate constants of (1.1 +/- 0.2) and (2.2 +/- 0.2) * 10-17 cm3 molecule-1 s-1.No reaction was observed between NO3 and methane or chloromethane, suggesting upper limits (based on the noise levels) for the overall rate constants of these reactions of 8 * 10-19 and 1* 10-18 cm3 molecule-1 s-1.
Rate Coefficient for the Reaction NO + NO3 -> 2NO2 between 223 and 400 K
Tyndall, G. S.,Orlando, J. J.,Cantrell, C. A.,Shetter, R. E.,Calvert, J. G.
, p. 4381 - 4386 (1991)
The rate coefficient for the reaction NO + NO3 -> 2NO2 (1) has been measured in a discharge flow system between 223 and 400 K.Measurements were made by laser-induced fluorescence detection of NO3 in the presence of excess NO or by chemiluminescent detection of NO in the presence of excess NO3.Analysis of the kinetics was made using a modified form of the usual flow equations, which explicitly accounts for the viscous pressure drop.The rate coefficients are in excellent agreement with the determination of Sander and Kircher (Chem.Phys.Lett. 1986, 126, 149).The recommended rate coefficient from this study and that of Sander and Kircher can be adequately described by the expression k1 = (1.65 +/- 0.35) x 10-11e cm3 molecule-1 s-1.The possible effects of secondary chemistry on the rate coefficients determined are discussed.
Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K
Jimenez, Elena,Gierczak, Tomasz,Stark, Harald,Burkholder, James B.,Ravishankara
, p. 1139 - 1149 (2004)
HO2NO2 (peroxynitric acid, PNA) has an important role in determining the ozone abundance and its changes over time in the lower stratosphere. Rate coefficients (k3(T)) for the reaction of OH with PNA in the gas phase were
Manganese porphyrins as redox-coupled peroxynitrite reductases
Lee, Jinbo,Hunt, Julianne A.,Groves, John T.
, p. 6053 - 6061 (1998)
Superoxide (O2.-) and peroxynitrite (ONOO-) have been implicated in many pathophysiological conditions. To develop novel catalysts that have both ONOO- decomposition and O2.- dismutase activity, and to understand the mechanisms of these processes, we have explored the reactivity of 5,10,15,20-tetrakis- (N-methyl-4'-pyridyl)porphinatomanganese(III) [Mn(III)TMPyP] toward ONOO- and 02.-. The reaction of Mn(III)TMPyP with ONOO- to generate an oxomanganese(IV) porphyrin species [(oxoMn(IV)] is fast, but Mn(III)TMPyP is not catalytic for ONOO- decomposition because of the slow reduction of oxoMn(IV) back to the Mn(III) oxidation state. However, biological antioxidants such as ascorbate, glutathione, and Trolox rapidly turn over the catalytic cycle by reducing oxoMn(IV). Thus, Mn(III)TMPyP becomes an efficient peroxynitrite reductase when coupled with ascorbate, glutathione, and Trolox (k(c) ~2 x 106 M-1 s-1), though the direct reactions of ONOO- with these biological antioxidants are slow (88 M-1 s-1, 5.8 x 102 M-1 s-1 and 33 M-1 s-1, respectively). Mn(III)TMPyP is known to catalyze the dismutation of O2.-, and using stopped-flow spectrophotometry, the rate of Mn(III)TMPyP-catalyzed dismutation has been measured directly (k(c) = 1.1 x 107 M-1 s-1). Further, O2.-, like the biological antioxidants, rapidly reduces oxoMn(IV) to the Mn(III) oxidation state (k ~108 M-1 s-1), transforming Mn(III)TMPyP into a O2.--coupled ONOO- reductase. Under conditions of oxidative stress and reduced antioxidant levels, Mn(III)TMPyP may deplete O2.- primarily as a function of its ONOO- reductase activity, and not through its O2.- dismutase activity.
Extracellular hydrogen peroxide measurements using a flow injection system in combination with microdialysis probes – Potential and challenges
Mo?hammer, Maria,Schrameyer, Verena,Jensen, Peter ?.,Koren, Klaus,Kühl, Michael
, p. 111 - 123 (2018)
There is a strong need for techniques that can quantify the important reactive oxygen species hydrogen peroxide (H2O2) in complex media and in vivo. We combined chemiluminescence-based H2O2 measurements on a commercially available flow injection analysis (FIA) system with sampling of the analyte using microdialysis probes (MDPs), typically used for measurements in tissue. This allows minimally invasive, quantitative measurements of extracellular H2O2 concentration and dynamics utilizing the chemiluminescent reaction of H2O2 with acridinium ester. By coupling MDPs to the FIA system, measurements are no longer limited to filtered, liquid samples with low viscosity, as sampling via a MDP is based on a dynamic exchange through a permeable membrane with a specific cut-off. This allows continuous monitoring of dynamic changes in H2O2 concentrations, alleviates potential pH effects on the measurements, and allows for flexible application in different media and systems. We give a detailed description of the novel experimental setup and its measuring characteristics along with examples of application in different media and organisms to highlight its broad applicability, but also to discuss current limitations and challenges. The combined FIA-MDP approach for H2O2 quantification was used in different biological systems ranging from marine biology, using the model organism Exaiptasia pallida (light stress induced H2O2 release up to ~ 2.7 μM), over biomedical applications quantifying enzyme dynamics (glucose oxidase in a glucose solution producing up to ~ 60 μM H2O2 and the subsequent addition of catalase to monitor the H2O2 degradation process) and the ability of bacteria to modify their direct environment by regulating H2O2 concentrations in their surrounding media. This was shown by the bacteria Pseudomonas aeruginosa degrading ~ 18 μM background H2O2 in LB-broth. We also discuss advantages and current limitations of the FIA-MDP system, including a discussion of potential cross-sensitivity and interfering chemical species.
Complexes formed between nitrilotris(methylenephosphonic acid) and M2+ transition metals: Isostructural organic-inorganic hybrids
Cabeza, Aurelio,Ouyang, Xiang,Sharma, C. V. Krishnamohan,Aranda, Miguel A. G.,Bruque, Sebastian,Clearfield, Abraham
, p. 2325 - 2333 (2002)
Nitrilotris(methylenephosphonic acid) (NTP, [N(CH2PO3H2)3]) recently has been found to form three-dimensional porous structures with encapulation of templates as well as layered and linear structures with template intercalation. It was, therefore, of interest to examine the type of organic-inorganic hybrids that would form with metal cations. Mn(II) was found to replace two of the six acid protons, while a third proton bonds to the nitrilo nitrogen, forming a zwitter ion. Two types of compounds were obtained. When the ratio of acid to Mn(II) was less than 10, a trihydrate, Mn[HN(CH2PO3H)3(H2O)3] (2) formed. Compound 2 is monoclinic P21/c, with a = 9.283(2) A, b = 16,027(3) A, c = 9,7742(2) A, β = 115.209(3)°, V = 1315,0(5) A3, and Z= 4. The Mn atoms form zigzag chains bridged by two of the three phosphonate groups, The third phosphonate group is only involved in hydrogen bonding. The metal atoms are octahedrally coordinated with three of the sites occupied by water molecules, Adjacent chains are hydrogen-bonded to each other through POH and HN donors, and the additional participation of all the water hydrogens in H-bonding results in a corrugated sheetlike structure. Use of excess NTP at a ratio to metal of 10 to 1 yields an anhydrous compound Mn[HN(CH2PO3H)3] (1), P21/n, a = 9,129(1) A, b = 8,408(1) A, c = 13,453(1) A, β = 97,830(2)°, V = 1023,0(2) A3, and Z = 4, Manganese is five coordinate forming a distorted square pyramid with oxygens from five different phosphonate groups. The sixth oxygen is 2,85 A from an adjacent Mn, preventing octahedral coordination. All the protonated atoms, three phosphonate oxygens and N, form moderately strong hydrogen bonds in a compact three-dimensional structure. The open-structured trihydrate forms a series of isostructural compounds with other divalent transition metal ions as well as with mixed-metal compositions. This is indicative that the hydrogen bonding controls the type of structure formed irrespective of the cation.
Synthesis and Identification by Infrared Spectroscopy of Gaseous Nitryl Bromide
Finlayson-Pitts, Barbara J.,Livingston, Frank E.,Berko, Henry N.
, p. 4397 - 4400 (1989)
The reactions at 298 K of gaseous N2O5 with NaBr(s) or with BrNO(g) in 1 atm of helium were followed by using Fourier transform infrared spectroscopy.In both cases, the formation of infrared absorption bands at 787, 1292, and approximately 1660 cm-1
