30525-89-4Relevant articles and documents
Oxathiirane
Schreiner, Peter R.,Reisenauer, Hans Peter,Romanski, Jaroslaw,Mloston, Grzegorz
, p. 7240 - 7241 (2010)
We describe the first preparation of the long-sought parent oxathiirane from sulfine through photochemical rearrangement with light at λ = 313 ± 10 nm in an Ar matrix at 11 K. Oxathiirane was characterized by the extraordinarily good agreement of experime
Hexagonal Orthovanadates as Catalysts in the Oxidation of Methanol to Formaldehyde
Salagre, Pilar,Sueiras, Jesus E.
, p. 1084 - 1085 (1988)
Improved selectivities are obtained in the catalytic oxidation of methanol to formaldehyde using hexagonal orthovanadates of the type Sr3-xLa2x/3(VO4)2 (x=0.3-1.5) in comparison with those using the strontium and lanthanum orthovanadates separately.
Kinetics and mechanism of the reaction of CH3O with NO
Dobe,Lendvay,Szilagyi,Berces
, p. 887 - 901 (1994)
The kinetics of the reaction of CH3O with NO and the branching ratio for HCHO product formation, obtained as ΓHCHO = (Rate of HCHO formation) / (Rate of CH3O decay), have been studied using a discharge flow reactor. Laser induced fluorescence has been used to monitor the decay of the CH3O radical and the build-up of the HCHO product. Overall rate constants and product branching ratios were measured at room temperature over the pressure range of 0.72-8.5 torr He. Three reaction mechanisms were considered which differed in the routes of HCHO formation: (i) direct disproportionation; (ii) via an energized collision complex; or (iii) both reaction routes. It has been shown that data on the pressure dependence of the overall rate constant are not sufficient to distinguish between these mechanisms. In addition, an accurate value of ΓHCHO∞ is required. Analysis of the available experimental data provided 0.0 and about 0.1 as the lower and upper limit for ΓHCHO∞, respectively. Since the rate constants derived for CH3ONO formation were not sensitive to the value assumed for ΓHCHO∞, kCH(3)ONO0 = (1.69 ± 0.69) × 10-29 cm6 molecule-2 s-1 and kCH(3)ONO∞ = (2.45 ± 0.31) × 10-11 cm3 molecule-1 s-1 could be derived. The rate constant obtained for formaldehyde formation when extrapolated to zero pressure is kHCHO0 = (3.15 ± 0.92) × 10-12 cm3 molecule-1 s-1.
Improved anticonvulsant activity of phenytoin by a redox brain delivery system II: Stability in buffers and biological materials
Murakami,Shek,Pop,Bodor
, p. 732 - 737 (1989)
The stability of nine chemical delivery systems (CDSs) for phenytoin (DPH) was studied in aqueous buffers and in biological materials. The systems were based on a dihydropyridune ? quaternary pyridinium salt redox pair attached to 3-(hydroxymethyl)phenytoin via an ester linkage. The pyridinium derivatives released DPH in aqueous buffers and their hydrolytic reactivity was consistent with their chemical structure. Although in rat blood and plasma all pyridinium esters hydrolyzed rapidly, there was a wide range in the hydrolysis rates in rat brain homogenate. The sterically hindered 1-alkylcarboxynicotinamide was the least reactive ester (t( 1/2 ) = 98.2 min), while the trigonellylglycolate ester was the fastest to hydrolyze enzymatically (t( 1/2 ) = 2 min) in rat brain homogenate. In acidic media, the major products of all dihydropyridine esters were the corresponding water adducts, the 6-hydroxy-1,4,5,6-tetrahydropyridines. These adducts were of no significance in biological materials. After comparison of the relative stability of the corresponding pairs of dihydropyridine and pyridinium ion in brain homogenate and the absolute stability of the various dihydropyridines, two CDSs were chosen for further in vivo evaluations. The CDSs chosen were the dihydrotrigonellinate ester and its 6-methyl derivative.
Oxidative degradation of norfloxacin by a lipophilic oxidant, cetyltrimethylammonium permanganate in water-acetonitrile medium: A kinetic and mechanistic study
Garnayak, Sarita,Patel, Sabita
, p. 327 - 335 (2015)
The present study reports the oxidative metabolism of an established antibacterial drug norfloxacin (NRF) by a lipid compatible lipophilic Mn(VII) oxidant, cetyltrimethylammonium permanganate (CTAP) in acetonitrile-water binary mixture in the presence of acetic acid. The metabolized products are identified as 7-amino-1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid, formaldehyde, and ammonia. The kinetics of the reaction is studied in aqueous acetonitrile media in the presence of acetic acid by UV-vis spectroscopic method by monitoring the absorbance of Mn(VII) at 530 nm under pseudo first-order condition. The reaction is found to be first-order with respect to CTAP and fractional order with respect to norfloxacin and acetic acid. Occurrence of Michaelis-Menten type kinetics with respect to norfloxacin confirmed the binding of oxidant and substrate to form a complex before the rate determining step. A suitable ionic mechanism is proposed based on the experimental findings. The proposed reaction mechanism is supported by the effect of solvent polarity and effect of temperature on the reaction rate. High negative entropy of activation (ΔS≠ = - 259 to - 158 J K- 1 mol- 1) supported the existence of a forced, more ordered and extensively solvated transition state. Further, solvent polarity-reactivity relationship revealed (i) the presence of less polar transition state compared to the reactants, (ii) differential contribution from dipolar aprotic (acetonitrile) and polar protic (water) solvents toward the reaction process through specific and nonspecific solute-solvent interaction and (iii) presence of intramolecular H-bonding in oxidant-substrate complex in acetonitrile rich domain and intermolecular H-bonding between oxidant-substrate complex and water in water rich domain.
The ethene-ozone reaction in the gas phase
Neeb, Peter,Horie, Osamu,Moortgat, Geert K.
, p. 6778 - 6785 (1998)
The ethene-ozone reaction was investigated in a 570 L spherical glass reactor at atmospheric pressure, using long-path FTIR spectroscopy for detection of the individual products. Experiments were performed in the presence of hydroxy and carbonyl compounds to identify the reactions of the Criegee intermediate CH2OO formed in ethene ozonolysis. Using 13C-labeled HCHO, this reaction was found to proceed via an unstable cyclic adduct which decays to the detected products HCHO, HCOOH and CO. [CH2OO + HCHO → HCHO + HCOOH (eq 13); CH2OO + HCHO → HCHO + CO + H2O (eq 14a); CH2OO + HCHO → HCHO + HCO + OH (eq 14b)] The relative rates of the reactions of CH2OO with HCOOH and HCHO were determined from the product analysis. In addition, evidence was found that the reaction of CH3CHO with the CH2OO intermediate does not exclusively produce secondary propene ozonide, but also HCHO and CO2. The results of this study have been combined with data from previous investigations to give a complete description of the gas phase ozonolysis of ethene and are discussed in comparison with ozonolysis reactions occurring in the liquid phase.
deLarambergue
, p. 1431 (1936)
Atmospheric Degradation of CH2=C(CH3)C(O)OCH3 Initiated by OH Radicals: Mechanistic Study and Quantification of CH3C(O)C(O)OCH3 in NOx Free Air
Gibilisco, Rodrigo G.,Uranga, Jorge G.,Santiago, Ana N.,Teruel, Mariano A.
, p. 8775 - 8783 (2015)
The product distribution of the gas-phase reaction of OH radicals with methyl methacrylate (CH2=C(CH3)C(O)OCH3, MMA) in the absence of NOx was studied at 298 K and atmospheric pressure of air. The experiments were performed in a Teflon chamber using solid-phase microextraction (SPME) with GC-MS and GC-FID for product identification and quantification, respectively. In the absence of NOx, methyl pyruvate (CH3C(O)C(O)OCH3) was identified with a yield of 76 ± 13% in accordance with the decomposition of the 1,2-hydroxyalkoxy radicals formed. In addition, a detailed quantum chemical study of the degradation of MMA was performed by density functional theory (DFT) methods using the MPWB1K functional. This calculation suggests that formation of methyl pyruvate, from C1-C2 scission of 1,2-hydroxyalkoxy radical, is kinetically and thermodynamically the most favorable reaction path taking into account the electronic properties of reaction intermediates and transition states. The difference observed on the degradation mechanism of MMA in the presence and absence of NOx was explained in terms of the associated thermochemistry. Furthermore, this study propose that reaction between peroxy radical (RO2?) and hydroxyl radical (OH) became relevant at NOx-free environments. This statement is in agreement with recent studies concerning small peroxy radicals such as CH3OO?.
μ-Nitrido-bridged iron phthalocyanine dimer bearing eight peripheral 12-crown-4 units and its methane oxidation activity
Yamada, Yasuyuki,Kura, Jyunichi,Toyoda, Yuka,Tanaka, Kentaro
, p. 19179 - 19183 (2020)
A novel μ-nitrido-bridged iron phthalocyanine dimer with eight peripheral 12-crown-4 units as an electron-donating substituent was synthesized and characterized. Examination of its methane oxidation activity in the presence of H2O2 in an acidic aqueous solution suggested that the high-valent iron oxo species generated in situ was unstable and the transiently generated decomposed species showed methane oxidation activity via Fenton-type reaction. This journal is
Sahasrabudhey et al.
, p. 258 (1952)
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Markham et al.
, p. 5394 (1958)
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Photoinduced Reactions of Methane with Molybdena Supported on Silica
Hill, Wieland,Shelimov, Boris N.,Kazansky, Vladimir B.
, p. 2381 - 2390 (1987)
Photoinduced reactions of methane on the surface on molybdena-silica have been studied using u.v. irradiation in the temperature range 293-773 K.During irradiation, photoadsorption of methane (up to 300 mmol of CH4 per mol of Mo) is found to be the predominant process with barely detectable formation of gaseous products.During heating of the irradiated samples from 293 to 473 K, in addition to thermodesorption of methane, wich reaches 40-50percent of photoadsorbed CH4, the desorption of considerable amounts of ethylene, ethane, hydrogen and smaller amounts of C3 and C4 alkenes and alkanes is observed.E.s.r., u.v.-visible and i.r. measurements of the irradiated samples show the presence of Mo5+ and Mo4+ ions as well as complexes of Mo4+ with olefins.The effects of O2, N2O and H2O on the photoinduced reactions of methane and on thermodesorption of the products have also been studied.Possible reaction mechanisms for the photoadsorption of methane and for the formation of C2 and higher hydrocarbons are discussed.
In operando imaging of self-catalyzed formaldehyde burst in methanol oxidation reactions under open circuit conditions
Yuan, Liang,Li, Meng,Yuan, Tinglian,Fang, Yimin,Wang, Wei
, p. 3318 - 3323 (2018)
We employ a surface plasmon resonance imaging (SPRi) technique to monitor the in operando process of formaldehyde (HCHO) production during methanol oxidation with high spatial and temporal resolutions. While common wisdom suggests HCHO is generated as an intermediate during continuous electron transfer towards CO2, we find that the majority of HCHO is produced via self-catalyzed chemical and electrochemical reactions under open-circuit conditions, which lead to an unprecedented HCHO burst immediately after withdrawal of external potential. Because open-circuit conditions better represent the operating environments of practical direct methanol fuel cells (DMFCs), this work uncovers a hidden pathway of HCHO accumulation by adopting a quantitative and in operando SPRi technique for the first time. These theoretical and technical advances are anticipated to help the fundamental understanding of the comprehensive mechanism of methanol oxidation with implications for improving the performance of DMFCs.
Barusch et al.
, p. 2764 (1951)
Photocatalytically assisted hydrolysis of chlorinated methanes under anaerobic conditions
Calza, Paola,Minero, Claudio,Pelizzetti, Ezio
, p. 2198 - 2203 (1997)
The photocatalytic degradation of CCl4, CHCl3, and CH2-Cl2 over irradiated Ti02 has been investigated at pH 5 and pH 11 under anaerobic conditions. Chloromethanes degrade through combined reductive and oxidative processes. Photocatalytically assisted hydrolysis, given by sequential reactions involving ·OH/e-/H+, is 106-108 times faster than the corresponding thermal process. Dechlorination of chloromethanes is achieved with degradation rates in the order CCl4 > CHCl3 > CH2Cl2. Stable intermediates, either chlorinated (chloromethanes, C2Cl6, and C2Cl4) or dechlorinated (formic acid, formaldehyde, and methanol) have been quantified. The average carbon oxidation number n(c) remains almost unchanged at the end of the degradation process, although for CCl4 in the early stages it is markedly reduced with slow regrowth of n(c) toward the initial value. Reaction pathways accounting for the observed results are presented based on literature data concerning transient intermediates. The photocatalytic degradation of CCl4, CHCl3, and CH2-Cl2 over irradiated TiO2 has been investigated at pH 5 and pH 11 under anaerobic conditions. Chloromethanes degrade through combined reductive and oxidative processes. Photocatalytically assisted hydrolysis, given by sequential reactions involving ·OH/e-/H+, is 106-108 times faster than the corresponding thermal process. Dechlorination of chloromethanes is achieved with degradation rates in the order CCl4>CHCl3>CH2Cl2. Stable intermediates, either chlorinated (chloromethanes, C2Cl6, and C2Cl4)or dechlorinated (formic acid, formaldehyde, and methanol) have been quantified. The average carbon oxidation number nc remains almost unchanged at the end of the degradation process, although for CCl4 in the early stages it is markedly reduced with slow regrowth of nc toward the initial value. Reaction pathways accounting for the observed results are presented based on literature data concerning transient intermediates.
Methylperoxy Self-Reaction: Products and Branching Ratio between 223 and 333 K
Horie, O.,Crowley, J. N.,Moortgat, G. K.
, p. 8198 - 8203 (1990)
Products from Cl atom initiated oxidation of CH4 were analyzed by matrix isolation Fourier transform infrared spectroscopy (MI-FTIR) in order to determine the branching ratio k1a/k1 of the methylperoxy self-reaction: CH3O2 + CH3O2 -> CH3O + CH3O + O2 (1a); CH3O2 + CH3O2 -> HCHO + CH3OH + O2 (1b); and CH3O2 + CH3O2 -> CH3OOCH3 + O2 (1c).The value k1a/k1 = k1a/(k1a+k1b+k1c) showed a pronounced temperature dependence in the range 223 - 333 K and is given by the relationship k1a/k1 = 1/ /(19 +/- 5)>.These results are combined with previous measurements to make a recommendation for the temperature range 223 - 573 K: k1a/k1 = 1//(33 +/- 10)>.
Selective photo-assisted catalytic oxidation of methane and ethane to oxygenates using supported vanadium oxide catalysts
Wada, Kenji,Yamada, Hiroshi,Watanabe, Yoshihisa,Mitsudo, Take-Aki
, p. 1771 - 1778 (1998)
Selective photooxidation of light alkanes, mainly methane and ethane, into the corresponding aldehydes was achieved using silica-supported vanadium oxide catalysts under UV irradiation at elevated temperature. Photooxidation of methane using the V2O5/SiO2-IW (incipient wetness) (0.6 mol% V) catalyst at 493 K for 2 h gave 68 μmol of methanal, which corresponds to 76 mol% selectivity and 0.48 mol% one-pass yield. Photooxidation of ethane using V2O5/SiO2 (calcined at 1023 K) -IW (0.6 mol% V) catalyst for 1 h gave 85 μmol of ethanal, which corresponds to 90% selectivity and 1.1% one-pass yield. The catalysts prepared by the sol-gel method also showed activity, especially for the reaction of ethane. Both UV irradiation and a reaction temperature as high as 500 K were essential. The photo-assisted catalytic reactions were very sensitive to the reaction temperature, method of preparation of the catalyst, and addition of water vapour. While the reaction of methane was inhibited by the addition of water vapour, the photooxidation of ethane and propane was promoted in the presence of a controlled amount of water vapour. In addition, the reaction with methane required UV irradiation at a wavelength 2O5, were shown to be active for the photooxidation of ethane and propane.
Photocatalytic Hydrogen Evolution from Alcohols using Dodecawolframosilicic Acid and Colloidal Platinum
Darwent, James R.
, p. 798 - 799 (1982)
Illumination of dodecawolframosilicic acid and colloidal platinum leads to photocatalytic H2 evolution from alcohols with a quantum yield for H2 of 0.1 mol einstein-1.
Pd-Catalyzed Surface Reactions of Importance in Radiation Induced Dissolution of Spent Nuclear Fuel Involving H2
Maier, Annika Carolin,Jonsson, Mats
, p. 5108 - 5115 (2019)
To assess the influence of metallic inclusions (?-particles) on the dissolution of spent nuclear fuel under deep repository conditions, Pd-catalyzed reactions of H2O2, O2 and UO2 2+ with H2 were studied using Pd-powder suspensions. U(VI) can efficiently be reduced to less soluble U(IV) on Pd-particles in the presence of H2. The kinetics of the reaction was found to depend on the H2 partial pressure at pH2≤5.1×10?2 bar. In comparison, the H2 pressure dependence for the reduction of H2O2 on Pd also becomes evident below 5.1×10?2 bar. Surface bound hydroxyl radicals are formed as intermediate species produced during the catalytic decomposition of H2O2 on oxide surfaces. While a significant amount of surface bound hydroxyl radicals were scavenged during the catalytic decomposition of H2O2 on ZrO2, no scavenging was observed in the same reaction on Pd. This indicates a different reaction mechanism for H2O2 decomposition on Pd compared to metal oxides and is in contrast to current literature. While Pd is an excellent catalyst for the synthesis of H2O2 from H2 and O2, a similar catalytic activity that was previously proposed for ZrO2 could not be confirmed.
Amphiphilic/bipolar metallocorroles that catalyze the decomposition of reactive oxygen and nitrogen species, rescue lipoproteins from oxidative damage,and attenuate atherosclerosis in mice
Haber, Adi,Mahammed, Atif,Fuhrman, Bianca,Volkova, Nina,Coleman, Raymond,Hayek, Tony,Aviram, Michael,Gross, Zeev
, p. 7896 - 7900 (2008)
(Chemical Equation Presented) Antioxidans that work! The iron corrole 1-Fe (see picture) is a potetnt catalyst for decomposition of reactive oxygen and nitrogen species that binds selectively to lipoproteins. The complex also affects cholesterol levels and its cellular efflux. 1-Fe is more effective that natural antioxidants in reducing atherosclerosis development in mice. LDL = low-density lipoprotein.
High catalytic methane oxidation activity of monocationic μ-nitrido-bridged iron phthalocyanine dimer with sixteen methyl groups
Kura, Jyunichi,Tanaka, Kentaro,Toyoda, Yuka,Yamada, Yasuyuki
, p. 6718 - 6724 (2021)
Herein, we report the highly potent catalytic methane oxidation activity of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups. It was confirmed that this complex oxidized methane stably into MeOH, HCHO, and HCOOH in a catalytic manner in an acidic aqueous solution containing excess H2O2 at 60 °C. The total turnover number of the reaction reached 135 after 12 h, which is almost seven times higher than that of a monocatinoic μ-nitrido-bridged iron phthalocyanine dimer with no peripheral substituents. This suggests that the increased number of peripheral electron-donating substituents could have facilitated the generation of a reactive high-valent iron-oxo species as well as hydrogen abstraction from methane by the reactive iron-oxo species.
Reactions of C2H5 Radicals with O, O3, and NO3: Decomposition Pathways of the Intermediate C2H5O Radical
Hoyermann,Olzmann,Seeba,Viskolcz
, p. 5692 - 5698 (1999)
The reactions of C2H5 with O, O3, and NO3 have been investigated in a discharge flow reactor at room temperature and pressures between 1 and 3 mbar. The reaction products were detected by mass spectrometry with electron-impact ionization. The product pattern observed is explained in terms of the decomposition of an intermediately formed, chemically activated ethoxy radical. It is shown that, with this assumption, the experimentally determined branching ratios of the different product channels can be reproduced nearly quantitatively by RRKM calculations based on ab initio results for the stationary points of the potential energy surface of C2H5O. For C + O and C2H5 + O3, the existence of an additional, parallel channel leading to OH has to be assumed. High-pressure Arrhenius parameters for the unimolecular reactions of the ethoxy radical are given and discussed.
Thermolysis of 3-alkyl-3-methyl-1,2-dioxetanes: Activation parameters and chemiexcitation yields
Baumstark, Alfons L.,Anderson, Sean L.,Sapp, Chariety J.,Vasquez, Pedro C.
, p. 459 - 462 (2001)
3-Methyl-3-(3-pentyl)-1,2-dioxetane 1 and 3-methyl-3-(2,2-dimethyl-1-propyl)-1,2-dioxetane 2 were synthesized in low yield by the α-bromohydroperoxide method. The activation parameters were determined by the chemiluminescence method (for 1 ΔH? = 25.0 ± 0.3 kcal/mol, ΔS? = -1.0 entropy unit (e.u.), ΔG? = 25.3 kcal/mol, k1 (60°C) = 4.6 × 10-4s-1. Thermolysis of 1-2 produced excited carbonyl fragments (direct production of high yields of triplets relative to excited singlets) (chemiexcitation yields) for 1: φT = 0.2, φ ≤ 0.0005; for 2: φT = 0.02 φS ≤ 0.0004). The results are discussed in relation to a radical-like mechanism.
Direct dehydrogenation of methanol to formaldehyde over novel Ag-containing ceramics
Dong, Yi,Dai, Wei-Lin,Li, Jia-Liang,Deng, Jing-Fa
, p. 534 - 535 (2001)
A novel silver-ceramics supported catalyst showing excellent activity and selectivity in the direct dehydrogenation of methanol to formaldehyde was prepared. The selectivity was as high as 100% and the yield of formaldehyde reached 70%.
Pt+-catalyzed oxidation of methane: Theory and experiment
Pavlov, Maria,Blomberg, Margarete R. A.,Siegbahn, Per E. M.,Wesendrup, Ralf,Heinemann, Christoph,Schwarz, Helmut
, p. 1567 - 1579 (1997)
The oxidation of methane with molecular oxygen using the atomic platinum cation as a catalyst, yielding methanol, formaldehyde, and higher oxidation products, has been studied both computationally and experimentally. The most relevant reaction pathways have been followed in detail. To this end a large number of stationary points, both minima and transition states, have been optimized using a hybrid density functional theory method (B3LYP). At these optimized geometries, energies have been calculated using both an empirical scaling scheme (PCI-80) and the B3LYP method employing extended basis sets with several polarization functions. Good agreement with available experimental data has been obtained. For the parts of the catalytic cycle where detailed experimental results have not been available, the new calculated results have complemented the experimental picture to reach an almost complete understanding of the reaction mechanisms. Spin-orbit effects have been incorporated using an empirical approach, which has lead to improved agreement with experiments. The new FTICR experiments reported in the present study have helped to clarify some of the most complicated reaction sequences.
Unprecedentedly high efficiency for photocatalytic conversion of methane to methanol over Au-Pd/TiO2-what is the role of each component in the system?
Cai, Xiaojiao,Fang, Siyuan,Hu, Yun Hang
supporting information, p. 10796 - 10802 (2021/05/14)
Direct and highly efficient conversion of methane to methanol under mild conditions still remains a great challenge. Here, we report that Au-Pd/TiO2 could directly catalyze the conversion of methane to methanol with an unprecedentedly high methanol yield of 12.6 mmol gcat-1 in a one-hour photocatalytic reaction in the presence of oxygen and water. Such an impressive efficiency is contributed by several factors, including the affinity between Au-Pd nanoparticles and intermediate species, the photothermal effect induced by visible light absorption of Au-Pd nanoparticles, the employment of O2 as a mild oxidant, and the effective dissolution of methanol in water. More importantly, for the first time, thermo-photo catalysis is demonstrated by the distinct roles of light. Namely, UV light is absorbed by TiO2 to excite charge carriers, while visible light is absorbed by Au-Pd nanoparticles to increase the temperature of the catalyst, which further enhances the driving force of corresponding redox reactions. These results not only provide a valuable guide for designing a photocatalytic system to realize highly efficient production of methanol, but also, highlight the great promise of thermo-photo catalysis. This journal is
Method for preparing formaldehyde by photocatalytic oxidation of ethylene glycol
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Paragraph 0007; 0033-0080, (2021/05/26)
The invention provides a method for preparing formaldehyde from ethylene glycol by photocatalytic oxidation. According to the method, ethylene glycol is taken as a substrate, air or oxygen is taken asan oxygen source, and a C-C bond cracked product, namely, formaldehyde can be generated under illumination in presence of a catalyst. The conditions are mild, the oxidation efficiency and the productyield are high, and the air or the oxygen is taken as the oxygen source under the illumination condition, so that the method is economical, environmentally friendly and green, meets the strategy of sustainable developed energy and has broad application prospect.
