- Chemical and Electrochemical Oxidation of Solutions of Silver Nitrate in Acetonitrile
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In anhydrous acetonitrile the unstable, brown species Ag(NO3)42-, I, can be produced either by the electrolysis of silver nitrate or by the equilibrium reaction N2O5 + Ag+ + 3NO3- ->/-3.The ESR spectrum of I at 77 K is that of a Ag(II) ion in a field with pronounced axial distortion.Its resonance Raman spectrum indicates square-planar coordination of the metal ion by unidentate nitrate ligands.The complex decomposes to form cyanomethyl nitrate and nitric acid by the rate law -d/dt = k/->.In the presence of p-xylene a major organic product is p-methylbenzyl nitrate.Equilibrium and electrochemical studies lead to estimated ΔG0298 values for the free radical and ionic dissociation pathways of N2O5 in acetonitrile solution of +38 and -26 kJ, respectively.
- Tracy, Mark L.,Nash, Charles P.
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- Kinetics and mechanism of oxidation of nitrous acid by chlorite ion
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Although the oxidation of nitrite by chlorite both stoichiometrically and kinetically is a fairly simple reaction when nitrite is in excess and the pH is above 4, it becomes exceedingly complex in acidic solution containing chlorite in excess. Cl2O2 appears to be a key intermediate, the transitory formation of which explains both the formation of ClO2 and peculiar three-extrema E versus time curve. Assuming that the electrode process on the bright Pt electrode is HOCl + e- + H+ = Cl2 + H2O, the reaction is an oligooscillatory one in which the concentration of HOCl exhibits three extrema at most.
- Lengyel, Istvan,Gaspar, Vilmos,Beck, Mihaly T.
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- Nucleophile Assistance of Electron-Transfer Reactions between Nitrogen Dioxide and Chlorine Dioxide Concurrent with the Nitrogen Dioxide Disproportionation
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The reaction of chlorine dioxide with excess NO2- to form ClO2- and NO3- in the presence of a large concentration of ClO2- is followed via stopped-flow spectroscopy. Concentrations are set to establish a preequilibrium among ClO2, NO2-, ClO2-, and an intermediate, NO2. Studies are conducted at pH 12.0 to avoid complications due to the ClO2-/NO2- reaction. These conditions enable the kinetic study of the ClO2 reaction with nitrogen dioxide as well as the NO2 disproportionation reaction. The rate of the NO2/ClO2 electron-transfer reaction is accelerated by different nucleophiles (NO2- > Br- > OH- > CO32- > PO43- > ClO2- > H 2O). The third-order rate constants for the nucleophile-assisted reactions between NO2 and ClO2 (kNu, M -2 s-1) at 25.0 °C vary from 4.4 × 10 6 for NO2- to 2.0 × 103 when H2O is the nucleophile. The nucleophile is found to associate with NO2 and not with ClO2 in the rate-determining step to give NuNO2+ + ClO2-. The concurrent NO2 disproportionation reaction exhibits no nucleophilic effect and has a rate constant of 4.8 × 107 M-1 s -1. The ClO2/NO2/nucleophile reaction is another example of a system that exhibits general nucleophilic acceleration of electron transfer. This system also represents an alternative way to study the rate of NO2 disproportionation.
- Becker, Robert H.,Nicoson, Jeffrey S.,Margerum, Dale W.
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- Spontaneous reactions and reduction by iodide of peroxynitrite and peroxynitrate: mechanistic insight from activation parameters
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Thermal and pressure activation parameters are reported for the decomposition of peroxynitrate, isomerization of peroxynitrite, and their reduction by iodide in aqueous solutions. The spontaneous decomposition reactions are characterized by activation ent
- Goldstein,Meyerstein,van Eldik,Czapski
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- HYPOCHLORITE OXIDATION OF AMMONIA. EFFECTIVE REMOVAL OF AMMONIA FROM WASTE WATER BY UV-IRRADIATION.
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The hypochlorite oxidation of ammonia giving rise to nitrogen evolution was carried out in the dark or under irradiation in order to study the reaction mechanism and application to waste water treatment. UV-irradiation accelerates remarkably the rate of decomposition of unfavorable chloramines. The acceleration covers the pH region 2-12, where corresponding dark reactions are slow. The irradiation also affects the formation of byproducts such as NO//2** minus and NO//3** minus , the effect being a slight increase in NO//2** minus formation in the pH range 2-12. These results suggest an effective industrial application to avoid eutrophication in seas and lakes. The irradiation effect is discussed in relation to reaction mechanism, in which the irradiation possibly facilitates the N-N bond formation after chloramine formation.
- Kimura,Suzuki,Ogata
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- Enhanced photocatalytic degradation of methylene blue under vacuum ultraviolet irradiation
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A vacuum ultraviolet (VUV) lamp was used as the irradiation of photocatalysis to enhance the degradation of methylene blue (MB), a model dye compound. In contrast to photocatalysis under 254 nm UV irradiation (UV/TiO 2), photocatalysis under VUV irradiation (VUV/TiO2) exhibited much higher efficiency in MB degradation and mineralization and needed less TiO2 dosage. The rate constant of MB degradation in VUV/TiO2 (0.0793 min-1) is about 4 times of that of UV/TiO2 (0.0205 min-1). The MB mineralization rate is also greatly increased from 12.5% in UV/TiO2 to 47.7% in VUV/TiO 2 after 60 min of irradiation. Multiple advanced oxidation processes including photocatalytic oxidation and VUV photo-oxidation coexist in VUV/TiO2 to substantially produce highly reactive species (such as OH and energetic photons), which is responsible for efficient degradation and mineralization of MB.
- Huang, Haibao,Leung, Dennis Y.C.,Kwong, Philip C.W.,Xiong, Jing,Zhang, Lu
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- NMR study of reactions between Pd, Ru, and Rh nitrite complexes with sulfamic acid
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Reactions of nitrite complexes of Pd, Ru, and Rh with sulfamic acid were studied by the 14, 15N, and 17O NMR method. Chemical shifts were assigned, and the predominant forms of the complexes were established. The reaction products at room temperature are cis-nitroaqua complexes. Coordination of the sulfamate ion upon storage for a long time or on heating was detected.
- Belyaev,Emel'yanov,Khranenko,Fedotov
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- The role of cobalt oxide or magnesium oxide in ozonation of ammonia nitrogen in water
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In this study, the reaction mechanisms for ozonation of ammonia nitrogen in the presence of Co3O4 or MgO were investigated. For the reaction over Co3O4, Cl– in the reaction solution was indispensable and ClO– was formed by a non-catalytic oxidation of Cl–. Co3O4 promoted the reaction of NH4+ with ClO– to give the products including NO3–, chloramines and gaseous products. In contrast, Cl– was unnecessary for the reaction with MgO. pH of the reaction solution was maintained at around 9 throughout the reaction owing to partial dissolution of MgO. Ammonia nitrogen was decomposed to mainly NO3– by non-catalytic radical reaction involving OH·, which was formed by the reaction of OH– with O3 in weakly basic solution. To keep the reaction solution weakly basic, H+ formed with the decomposition of NH4+ was neutralized. As a result, about the same amount of Mg2+ as that of decomposed ammonia nitrogen was dissolved.
- Anggo Krisbiantoro, Philip,Togawa, Tomokazu,Mahardiani, Lina,Aihara, Haruka,Otomo, Ryoichi,Kamiya, Yuichi
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- Nanopore enriched hollow carbon nitride nanospheres with extremely high visible-light photocatalytic activity in the degradation of aqueous contaminants of emerging concern
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Construction of highly efficient hollow nanosphere photocatalytic systems has been strongly attracting the attention of researchers. In the present work, nanopore enriched hollow carbon nitride nanospheres (HCNNSs) with a smaller particle size (200 nm) and a thinner shell thickness (40 nm) are successfully fabricated by a silica-nanocasting strategy. Such unique structures possess many advantages such as large BET surface area (122 m2 g-1), high light-harvesting ability, fast charge separation and transfer efficiency, plentiful exposed active sites and enhanced oxidation ability of photogenerated holes (h+VB). Therefore, HCNNSs in smaller sizes (HCNNS-200) exhibit extremely excellent visible-light photocatalytic efficiency towards the degradation of contaminants of emerging concern, e.g. levofloxacin (LEVO), in comparison with bulk g-C3N4 and HCNNSs in larger sizes (HCNNS-500). And it takes less than 10 min to finish the degradation of LEVO. The experimental results including those from indirect chemical probing, electron spin resonance, ion chromatography and high performance liquid chromatography-mass spectrometry confirm that h+VB and O2- are the active species that are responsible for the mineralization of LEVO to NO3-, F-, H2O and CO2 under visible-light irradiation. Additionally, the degradation pathway of LEVO in the HCNNS-200 photocatalytic system is also proposed. It is expected that HCNNS-200 can be used as a promising photocatalyst for environmental remediation.
- Yang, Yuxin,Hu, An,Wang, Xinyue,Meng, Jiaqi,Guo, Yihang,Huo, Mingxin,Zhu, Suiyi
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p. 355 - 365
(2019/01/28)
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- Cold atmospheric plasma activated water as a prospective disinfectant: The crucial role of peroxynitrite
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The socio-economic, environmental, and health implications of diseases caused by pathogenic microorganisms and their treatment using conventional antimicrobials are significant. The increasing resistance to antibiotics and detrimental biological side effects of many common antibiotics on human health and on the ecosystem have driven the search for new cost-effective and highly-efficient sterilization treatments and agents that are more environmentally benign. Plasma activated water (PAW), a product of cold atmospheric plasma reacting with water, is a promising broad-spectrum biocidal agent whose biochemical activity is attributed to the presence of a rich diversity of highly reactive oxygen and nitrogen species (RONS). The transient activity of PAW, where PAW reverts to water within days of storage and application, suggests that it can become a green alternative to conventional chemical treatment methods, yet the issues of scale up and the not fully understood mechanism of activity remain. In this study, we sought to explore the antibiotic potential of PAW generated from a plasma jet in a continuous flow reactor and determine the individual and combined contribution of thus-generated reactive chemistries in PAW for organism inactivation. Treatment of Escherichia coli with PAW led to more than a 4-log reduction, while exposure to an equivalent single dose of hydrogen peroxide (H2O2), nitrate (NO3-) or nitrite (NO2-) to that found in PAW failed to attain the same level of reduction. Peroxynitrite was identified as a critical bioactive species, particularly under acidic conditions, originating from the synergistic plasma effects (like the reactions of H2O2, NO3-, NO2- and other existing short-lived species like OH radicals in PAW). This research successfully demonstrated the possibility of PAW being an effective environmentally benign disinfectant, the activity of which is closely linked to the generation of peroxynitrite, providing much needed insights into the fundamental aspects of PAW chemistry required for optimisation of the biochemical activity of PAW and translation of this decontamination strategy into real life applications.
- Zhou, Renwu,Zhou, Rusen,Prasad, Karthika,Fang, Zhi,Speight, Robert,Bazaka, Kateryna,Ostrikov, Kostya
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supporting information
p. 5276 - 5284
(2018/12/05)
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- Design and construction of a bifunctional magnetically recyclable 3D CoMn2O4/CF hybrid as an adsorptive photocatalyst for the effective removal of contaminants
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Herein, a magnetic microsphere CoMn2O4 (MS-CoMn2O4) with a 3D architecture was constructed directly on cellulose fiber (CF) substrates from wastepaper by a solvothermal synthesis method with further calcination treatment. The designed hybrid shows excellent dual functions including rapid catalytic oxidation of tetracycline (TC)/methylene blue (MB) and a high adsorption capacity. What's more, the hybrid is easily recycled using an external magnetic field. In comparison with that of pure MS-CoMn2O4, the enhanced adsorption ability and photocatalytic activity of MS-CoMn2O4/CFs can mainly be attributed to the introduced cellulose fiber supporter in the hybrid system. MS-CoMn2O4 incorporated CFs can improve the efficient separation of photogenerated electron-hole pairs and the transport pathway of electrons. More importantly, introduction of CFs can help to enrich and further improve the degradation efficiency of organic contaminants. The possible mechanism for the enhancement of the photocatalytic activity has been elucidated in detail. The reusability analysis revealed that the MS-CoMn2O4/CF hybrid exhibited superb cycling stability after 5 cycles. This study provides novel insights into the design and construction of high capacity sorbents as strongly adsorptive photocatalysts to perform catalytic degradation of organic contaminants.
- Zheng, Jianhua,Hu, Yandong,Zhang, Lei
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p. 25044 - 25051
(2017/09/29)
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- Solvothermal preparation of Ag nanoparticle and graphene co-loaded TiO2 for the photocatalytic degradation of paraoxon pesticide under visible light irradiation
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The growing use of organophosphorus compounds such as paraoxon as agriculture pesticides results in their accumulation in soils and groundwater. Therefore there is a high demand for developing efficient methods for removing these materials from contaminated environmental resources. In this study, Ag nanoparticle and graphene co-loaded TiO2 with various contents of Ag and graphene was prepared via a facile surfactant free solvothermal method in a mixture of water and ethanol solvents and was applied, for the first time, for the photocatalytic degradation of paraoxon (as a model organophosphorus compound) under visible light irradiation. In this ternary nanocomposite, the presence of Ag nanoparticles is for narrowing the band gap to the visible region due to its surface plasmon resonance (SPR) effect and the presence of graphene is for diminishing the recombination rate of the photogenerated electron and holes due to its high electrical conductivity. The results of photocatalytic activity tests demonstrate that the nanocomposite with 6% wt Ag and 1% wt graphene content has the best photocatalytic activity among the products. Investigation of the chemical state of the nanocomposites showed that the covering of Ag nanoparticle loaded TiO2 with a high weight ratio of graphene resulted in the formation of Ag-O bonds through bonding of Ag to the oxygen functional groups of graphene which causes a decrease of the SPR effect of Ag and by this way decreases the photocatalytic activity. Gas Chromatography-Mass Spectrometry (GC-MS) was used as analytical tool for determination of the photocatalytic reaction intermediates. GC-MS analysis results show that photodegradation of paraoxon produces 4-nitrophenol, di-ethylphosphate, mono-ethylphosphate, hydroquinone and hydroxyhydroquinone as major intermediates and subsequent photodegradation of these results in complete mineralization of paraoxon.
- Keihan, Amir Homayoun,Hosseinzadeh, Reza,Farhadian, Mousa,Kooshki, Hamid,Hosseinzadeh, Ghader
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p. 83673 - 83687
(2016/11/05)
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- Synthesis and characterization of Pt/AgVO3 nanowires for degradation of atrazine using visible light irradiation
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A hydrothermal method was used to prepare β-AgVO3 nanowire, a photo-assisted deposition (PAD) method was used to prepare Pt/β-AgVO3 nanowires. β-AgVO3 and Pt/β-AgVO3 nanowires were characterized using XRD, BET, UV-Vis spectroscopy, Pl, TEM, and XPS techniques. The results reveal that platinum was present as platinum metal and it is well dispersed on the surface of β-AgVO3 nanowire. The photocatalytic degradation of atrazine under visible light irradiation was used to measure the photocatalytic performance of the β-AgVO3 and Pt/β-AgVO3 nanowires. The photocatalytic activity of Pt/β-AgVO3 nanowires have higher photocatalytic activity than β-AgVO3 nanowire. The reason for the high photocatalytic activity of Pt/β-AgVO3 nanowires may be due to the synergic effect between Pt and β-AgVO3.
- Malkhasian, Aramice Y.S.
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p. 394 - 399
(2015/08/06)
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- Enhancing the anion affinity of urea-based receptors with a Ru(terpy) 22+ chromophore
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Covalent linking of a Ru(terpy)22+ substituent improves recognition and sensing properties of the urea subunit toward anions. Urea's anion affinity is enhanced by the electrostatic attraction exerted by the RuII cation and by the electron-withdrawing effect exerted by the entire polypyridine-metal complex. Such an enhancement of the anion affinity, which results from the combination of a through-space and a through-bond effect, is greater than that exerted by the classical neutral electron-withdrawing substituent nitrophenyl. Small yet significant modifications of π-π* and MLCT bands of the Ru(terpy)22+ chromophore, detected through UV-vis spectrophotometric titrations, allowed the determination of the constants for the formation of receptor-anion H-bond complexes in diluted MeCN solution. On 1H NMR titration experiments, carried out under more concentrated conditions, the interaction of a second Cl- ion was observed, taking place through an outer-sphere mechanism. The Ru(terpy) 22+ substituent favors the deprotonation of a urea N-H fragment on addition of a second equivalent of fluoride, with formation of HF2-.
- Baggi, Giorgio,Boiocchi, Massimo,Ciarrocchi, Carlo,Fabbrizzi, Luigi
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p. 5273 - 5283
(2013/06/26)
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- Exploiting the synergy of titania and alumina in lean NOx reduction: In situ ammonia generation during the Pd/TiO2/Al 2O3-catalysed H2/CO/NO/O2 reaction
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In situ DRIFTS, XPS, HREM, XRD, and reactor studies have been used to examine and elucidate the catalytic performance of Pd particles supported on TiO2/Al2O3. These materials deliver 100% NOx conversion under demanding and technically relevant conditions (low temperature, high oxygen excess) in the presence of mixed H2+CO reductant feeds. In particular, they are far superior to the corresponding Pd/TiO2 and Pd/Al2O3 catalysts. It is shown that the synergy that operates between the titania and the alumina components involves the intrinsic surface chemistry of these oxides rather than formation of mixed oxide phases. Specifically, titania is critical for the formation of NCO on Pd while alumina promotes subsequent hydrolysis of NCO to ammonia, which then reduces NOx. At high temperature a second NOx reduction channel operates with Pd/TiO2/Al2O3 which greatly extends the useful temperature range. This also involves in situ formation of ammonia - in this case directly from reaction between H 2and NO.
- Macleod, Norman,Cropley, Rachael,Keel, James M.,Lambert, Richard M.
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- The rate and equilibrium constants for the reaction NO3? + Cl- ? NO3- + Cl? in aqueous solutions
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The rate and equilibrium constants for the reaction NO3? + Cl- ? NO3- + Cl? in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3?, and the dichloride radical anion, Cl2?-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.
- Poskrebyshev,Huie,Neta
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p. 1964 - 1970
(2007/10/03)
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- Kinetics and mechanism of electron transfer reactions in acetate buffers: Ruthenium (III) chloride catalysed oxidation of nitrite by thallium (III) acetate
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The oxidation of nitrite by thallium (III) in acetate buffers corresponds to the stoichiometry represented by Eq. The kinetic rate law (ii) accounts for the first order in each reactant and the retarding effect of acetate ions. [T1(III)], [HNO2] and [RuIII] are the gross analytical concentrations of the reactants and catalyst respectively. A plausible reaction mechanism has been suggested.
- Vijay,Sharma,Bhasin,Khandelwal,Sharma
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p. 708 - 713
(2007/10/03)
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- Simple and Complex pH Oscillations and Bistability in the Phenol-Perturbed Bromite-Hydroxylamine Reaction
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The unbuffered reaction between bromite and hydroxylamine at pH 3-7 has been studied under closed and open conditions.The stoichiometry of the batch system depends on the initial concentration ratio of the reactants and on the starting pH.The reaction is strongly autocatalytic in H+.Under flow conditions the reaction exhibits bistability between two steady states but does not oscillate.If the flow system is perturbated by an input of phenol, it shows oscillatory behavior in pH, potential of a Pt electrode, and color.A qualitative explanation of the batch and oscillatory behaviors is suggested.The bromite-hydroxylamine-phenol flow system can be characterized as a large-amplitude, long-period, pH-driven oscillator.
- Orban, Miklos,Epstein, Irving R.
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p. 2930 - 2935
(2007/10/02)
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- Electron transfer between azide and chlorine dioxide: The effect of solvent barrier nonadditivity
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The reaction of chlorine dioxide with excess azide in aqueous media proceeds with complex kinetics and produces N2, N2O, NO3-, Cl-, and ClO2-. In the presence of the spin trap PBN, the reaction is much simpler, and the rate law is -d [ClO2]/dt = k1 [ClO2] [N3-] [PBN]/([PBN] + [ClO2-]k-1/k2), with k1 = 809 M-1 s-1 and k-1/k2 = 19.0 at 25 °C. The inferred mechanism implies that k1 is the rate constant of electron transfer between ClO2 and N3-, k-1 is the reverse rate constant (N3 with ClO2-), and k2 is the rate constant for reaction of N3 with PBN. A dramatically lower value for k1 of 0.62 M-1 s-1 is calculated from the Marcus cross relationship and literature values for the self-exchange rates. The discrepancy is attributed to systematic errors in the literature self-exchange rates that were derived by applying the Marcus cross relationship to reactions of coordination complexes with N3- and ClO2. Such errors develop whenever this method is applied to reactions between species of widely differing size. Correcting for this effect leads to a calculated value of 56 M-1 s-1 for k1, which is in much improved agreement with the observed value. Similar corrections lead to greatly improved correlations for the self-exchange reaction of NO2 with NO2- and the electrontransfer reaction of ClO2 with NO2-.
- Awad,Stanbury
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p. 3636 - 3642
(2007/10/02)
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- Non-metal redox kinetics: A reexamination of the mechanism of the reaction between hypochlorite and nitrite ions
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Hypochlorite oxidation of NO2- does not take place by oxygen atom transfer, but proceeds by Cl+ transfer from HOCl to NO2- to give NO2Cl as a reaction intermediate. The kinetics indicate that the subsequent decomposition of NO2Cl proceeds by two pathways: loss of Cl- to give NO2+ and reaction of NO2Cl with NO2- to form N2O4 and Cl-. At high Cl- and low OH- and NO2- concentrations the overall rate of NO3- formation is suppressed by Cl-. The relative reactivities for the reaction with NO2+ are OH- ? Cl- ? H2O. Although oxygen isotope experiments are consistent with a Cl+ transfer mechanism, the rate of exchange of oxygen between OCl- and H2O is relatively rapid (even at high pH in the absence of Cl-). We predict that the OCl-/H2O exchange rate in base will be independent of OH- concentration.
- Johnson, Debra W.,Margerum, Dale W.
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p. 4845 - 4851
(2008/10/08)
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- Oxidation of Hydroxylamine by Periodate in a Continuous-Flow Stirred Tank Reactor: A New pH Oscillator
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The periodate oxidation of hydroxylamine exhibits a complex and variable stoichiometry at pH 5.There are two limiting cases.In excess periodate the products are nitrate and iodate, while in a large excess of hydroxylamine IO4- is reduced to I-, and the nitrogen-containing product is N2O.The formation of nitrite ion and iodine is important when neither of the reactants is present in large excess.The reaction shows clock type kinetics in closed conditions if no buffer is present.In a flow reactor sustained oscillations in +>, in color, and in redox potential are found experimentally in a narrow range of flow rate and input concentrations.A simple model is proposed to explain the oscillation.
- Rabai, Gyula,Epstein, Irving R.
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p. 7556 - 7559
(2007/10/02)
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- Kinetics and Mechanism of Uncatalyzed and Silver(I) Catalyzed Oxidations of Hydroxylamine with Peroxodiphosphate in Acetate Buffers
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Silver(I) catalyzed oxidation of hydroxylamine (HA) with peroxodiphosphate (PDP) studied in acetate buffers, is characterized by twelve reaction paths comprising (H2P2O8(2-) + H2O), (HP2O8(3-) + H2O), (H2P2O8(2-) + NH3OH(+)), (HP2O8(3-) + NH3OH(+)), (H2P2
- Gupta, Abhay K.,Gupta, Krishna S.,Gupta, Y. K.
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p. 653 - 659
(2007/10/02)
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- Sonolytic Decomposition of Nitrous Oxide in Aqueous Solution
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Water was insonated with 300-kHz ultrasound under pure argon, pure nitrous oxide, and mixtures of the two gases.The products of decomposition of N2O are N2, O2, NO2-, and small amounts of NO3-.Maximum yield of decomposition occurs at an Ar/N2O vol percent ratio of 85:15, the yield being comparable to that of the well-known CCl4-KI reaction.N2O is decomposed at a very low rate when water is insonated under pure nitrous oxide.H2O molecules and N2O molecules in argon bubbles containing a few percent N2O are decomposed with similar rates, although N2O is much more unstable than H2O.This observation is explained by postulating that all H2O molecules and N2O molecules in an argon bubble are converted into radicals in the short time of the adiabatic compression phase of a bubble.The yield of N2O decomposition increases with increasing gas pressure in a similar way as for other sonolytic reactions.
- Hart, Edwin J.,Henglein, Arnim
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p. 5992 - 5995
(2007/10/02)
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- Isotopic Exchange in the Sonolysis of Aqueous Solutions Containing 14,14N2 and 15,15N2
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Water was irradiated with 300-kHz ultrasonic waves under an atmosphere of argon and molecular nitrogen, the nitrogen being a 1/1 mixture of 14,14N2 and 15,15N2.Maximum yields of the nitrogen containing products, 14,15N2, NO2-, NO3-, NH3, and N2O, were observed for N2 concentrations between 40 percent and 60 percent in the gas atmosphere.The 14,15N2 yield was almost as large as that of NO2- + NO3-, while NH3 and N2O were present in much smaller amounts.The yields of H2O2, H2, and O2 were largest in the absence of N2 and continuously decreased with increasing N2 concentration.It is proposed that isotopic nitrogen exchange is a process accompanying the redox processes between O atoms, OH and H radicals, and nitrogen molecules.
- Hart, Edwin J.,Fischer, Ch.-Herbert,Henglein, Arnim
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p. 5989 - 5991
(2007/10/02)
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- Comportement electrochimique du nitrite et de l'acide nitreux dans le sulfolane
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The electrochemical oxidation of nitrite dissolved in anhydrous and deoxygenated sulfolane has been studied by means of the platinum rotating disk electrode and cyclic voltammetry.The nitrite ion undergoes two consecutive oxydation steps: 2 NO2(1-) NO + NO3(1-) + e(1-) : NO + NO3(1-) N2O4 +e(1-) .The reactions and are, respectively, reversible and quasi reversible charge transfers.An extensive study of the first anodic wave indicates that nitrogen dioxide and its dimer, dinitrogen tetroxide, occurs as intermediates according to: NO2(1-) NO2 + e(1-) ; NO2 1/2 N2O4 ; 1/2 N2O4 + NO2(1-) NO + NO3(1) .The kinetic constants are large and the sum + + gives the overall reaction .The normal potentials accounting for steps and and the equilibrium constant of the reaction were calculated.The mechanism of NO2(1-) oxidation is complicated by water at trace levels in sulfolane: the intermediate N2O4 formed by rection can disproportionate: N2O4 + H2O HNO2 + HNO3; and with excess N2O4: HNO2 + N2O4 N2O3 + HNO3.The species N2O3 and HNO2 (with nitrate) are electroactive: N2O3 NO + 1/2 N2O4 + e(1-) ; HNO2 + NO3(1-) HNO3 + 1/2 N2O4 + e(1-) .In this case, the voltammetric curves show tree consecutive oxidation steps.To elucidate this new mechanism, we have studied the electrochemical behaviour of nitrous acid with nitrate (reaction ).The results show that system is kinetically controlled, and becouse of the weak solubility of NO, nitrous acid is not stable in the presence of N2O4 and/or HNO3.
- Boughriet, A.,Fischer, J. C.,Leman, G.,Wartel, M.
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- Energetics and Mechanism of Acoustochemical Reactions. Yields of Hydrogen and Hydrogen Peroxide in Different Aqueous Systems
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Molecular hydrogen formed by the sonolysis of water in oxygen, nitrogen, and air atmospheres has been determined quantitatively.The initial rate of formation of hydrogen peroxide in water in a hydrogen atmosphere under the influence of ultrasound has been obtained.The concentration of oxygen in the cavitation bubble in the final phase of collapse has been calculated from the results.Under these conditions the oxygen is found to be a highly compressed fragment of plasma containing a small amount of vapour in the supercritical state.A mechanism which explains the dependence of the yield of the main sonolysis products of water in an N2 + O2 atmosphere on the concentration of oxygen is proposed.
- Margulis, M. A.,Didenko, Yu. T.
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p. 848 - 850
(2007/10/02)
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- PHOTOCATALYTIC REACTIONS OF AZIDE IONS ON PLATINIZED TITANIUM DIOXIDE POWDERS IN SOLUTIONS.
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Ammonia was formed photocatalytically from an aqueous solution of azide ion by using illuminated Pt/TiO//2 semiconductor powder. The reaction products, NH//3, N//2, and small amounts of N//2O and NO//3** minus , were detected. Hydrogen, O//2 and N//2H//4 were not formed in the primary reaction products. From these results, together with photoelectrochemical measurements, a mechanism of the ammonia formation from azide ion and water is presented.
- Nosaka,Ishizuka,Norimatsu,Miyama
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p. 3066 - 3069
(2007/10/02)
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- Gas-Phase Reactions of O- and O2- with a Variety of Halogenated Compounds
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The flowing afterglow technique has been applied to a comparative study, for a series of halogenated compounds, of dissociative attachment and reaction with O- and O2-.The ion product spectrum produced by reaction with O- and O2- overlaps but is more diverse than that obtained by dissociative attachment.Absolute rate constants for the O- and O2- reactions are reported.A few reactions, for which exothermic mechanisms can be written, were found to be quite inefficient.
- Streit, Gerald E.
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p. 2321 - 2324
(2007/10/02)
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- Heterogeneous Reactions of Nitrogen Monoxide on Titanium Dioxide Photocatalysts in Solutions
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Heterogeneous reactions of nitrogen monoxide on illuminated TiO2 catalysts in 1 mol dm-3 HClO4 were studied by electrochemical analysis.Nitrogen monoxide was reduced to ammonia and hydrazine.The main reaction was found to be a chemical reaction of hydroxylamine as a reaction intermediate with nitrogen monoxide to give molecular nitrogen.Nitrate was detected as an oxidation product formed by the counterpart reaction of the reduction of nitrogen monoxide.
- Yoneyama, Hiroshi,Shiota, Hisashi,Tamura, Hideo
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p. 1308 - 1313
(2007/10/02)
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- Energetics and Mechanism of Acoustochemical Reactions. VIII. Sonolysis of Iron and Cerium Sulphates in a Nitrogen Atmosphere and Determination of the Initial Acoustochemical Yields
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We have studied the kinetics of the oxidation of iron(II) sulphate and of the reduction of cerium(IV) sulphate in an acid solution exposed to ultrasound in a nitrogen atmosphere.The sonolysis of Ce4+ solutions has been studied in the presence of Tl+ ions.Equations for the energy yield of the sonolysis products have been obtained.The kinetic behaviour is explained by considering the main redox reactions possible in the systems examined.The acoustochemical efficiencies and the initial acoustochemical yields of products of the ultrasonic splitting of water molecules in a nitrogen atmosphere are calculated.The results are compared with predictions from the cavitation-diffusion theory of the propagation and reaction of radicals in an ultrasonic field.
- Margulis, M. A.,Didenko, Yu. T.
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p. 913 - 915
(2007/10/02)
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- Solvent effect on the rate of N(III)/Cl(V) reaction
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Kinetics of the reaction between N(III) and Cl(V) have been studied in water and water-dioxan solutions.The rate equation of the reaction in each solvent could be written as Rate=k3->+> and the rate rises as the dielectric constant of the medium is lowered.This observation is in accord with suggested mechanistic details involving the intermediate H2NClO5.
- Emeish, Samir S.
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p. 902 - 905
(2007/10/02)
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- A kinetic study of the oxidation of N(III) by ClO2- in aqueous acidic media
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Kinetics of the reaction between nitrous acid and chlorite have been studied spectrophotometrically.The rate equation involves terms 2>1.5 and 2->0.5, and both an uncatalysed and a chloride ion-catalysed path have been identified.A mechanism involving peroxonitrite and hypochlorous acid as intermediates is shown to be consistent with the observations.
- Emeish, Samir S.,Howlett, Keith E.
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p. 159 - 163
(2007/10/02)
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- Some chemistry of difluoraminocarbonyl chloride. A new route to perfluorourea
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Improved yields of NF2C(O)Cl are obtained by short-term (4-6 hr) photolysis of N2F4 with oxalyl chloride. Reactions of NF2C(O)Cl with AgCN, AgNCS, AgNCO, Hg(SCF3)2 and Hg(ON(CF3)2)2 give the new difluoraminocarbonyl pseudohalides NF2C(O)CN, NF2C(O)NCS, NF2C(O)NCO, NF2C(O)SCF3, and NF2C(O)ON(CF3)2. With excess of either Ag2O at 0° or HgO at -78°, NF2C(O)Cl is converted to (NF2)2CO and CO2 in nearly quantitative yield. Chlorocarbonyl fluorosulfate results when NF2C(O)Cl is mixed with S2O6F2 or BrOSO2F.
- Wright, Kenneth J.,Shreeve, Jean'ne M.
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