- IR spectroscopic study of the dichloromethyl peroxyl radical and its deuterated analogs in the argon matrix
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The dichloromethyl peroxyl radical (CHCl2OO?) and its deuterated analog formed in the reaction of the corresponding dichloromethyl radicals with O2 were studied by matrix IR spectroscopy. Dichloromethyl radicals are genera
- Baskir, E. G.,Nefedov, O. M.
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p. 2236 - 2240
(2022/01/22)
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- Photochemistry of a 9-Dithianyl-Pyronin Derivative: A Cornucopia of Reaction Intermediates Lead to Common Photoproducts
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Leaving groups attached to the meso-methyl position of many common dyes, such as xanthene, BODIPY, or pyronin derivatives, can be liberated upon irradiation with visible light. However, the course of phototransformations of such photoactivatable systems can be quite complex and the identification of reaction intermediates or even products is often neglected. This paper exemplifies the photochemistry of a 9-dithianyl-pyronin derivative, which undergoes an oxidative transformation at the meso-position to give a 3,6-diamino-9H-xanthen-9-one derivative, formic acid, and carbon monoxide as the main photoproducts. The course of this multi-photon multi-step reaction was studied under various conditions by steady-state and time-resolved optical spectroscopy, mass spectrometry and NMR spectroscopy to understand the effects of solvents and molecular oxygen on individual steps. Our analyses have revealed the existence of many intermediates and their interrelationships to provide a complete picture of the transformation, which can bring new inputs to a rational design of new photoactivatable pyronin or xanthene derivatives.
- Martínek, Marek,Váňa, Ji?í,?ebej, Peter,Navrátil, Rafael,Slanina, Tomá?,Ludvíková, Lucie,Roithová, Jana,Klán, Petr
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p. 2230 - 2242
(2020/08/05)
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- Direct Synthesis of 2-Formylpyrrolidines, 2-Pyrrolidinones and 2-Dihydrofuranones via Aerobic Copper-Catalyzed Aminooxygenation and Dioxygenation of 4-Pentenylsulfonamides and 4-Pentenylalcohols
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A new method for the direct conversion of 4-pentenylsulfonamides to 2-formylpyrrolidines and a 2-ketopyrrolidine has been developed. This transformation occurs via aerobic copper-catalyzed alkene aminooxygenation where molecular oxygen serves as both oxidant and oxygen source. The 2-formylpyrrolidines can further undergo oxidative carbon-carbon bond cleavage in situ upon addition of DABCO, providing 2-pyrrolidinones. These transformations have been demonstrated for a range of 4-pentenylsulfonamides. 4-Pentenylalcohols also undergo oxidative cyclization to form γ-lactones predominantly. The reaction is chemoselective, oxidizing one alkene in the presence of others, and is compatible with several functional groups. Application of these reactions to the formal syntheses of baclofen and (+)-monomorine was demonstrated.
- Wdowik, Tomasz,Chemler, Sherry R.
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supporting information
p. 9515 - 9518
(2017/07/25)
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- Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope-Labeled Reactants
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The low-temperature ethanol steam reforming (ESR) reaction mechanism over a supported Rh/Pt catalyst has been investigated using isotope-labeled EtOH and H2O. Through strategic isotope labeling, all nonhydrogen atoms were distinct from one another, and allowed an unprecedented level of understanding of the dominant reaction pathways. All combinations of isotope- and non-isotope-labeled atoms were detected in the products, thus there are multiple pathways involved in H2, CO, CO2, CH4, C2H4, and C2H6product formation. Both the recombination of C species on the surface of the catalyst and preservation of the C?C bond within ethanol are responsible for C2product formation. Ethylene is not detected until conversion drops below 100 % at t=1.25 h. Also, quantitatively, 57 % of the observed ethylene is formed directly through ethanol dehydration. Finally there is clear evidence to show that oxygen in the SiO2-ZrO2support constitutes 10 % of the CO formed during the reaction.
- Crowley, Stephen,Castaldi, Marco J.
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supporting information
p. 10650 - 10655
(2016/09/03)
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- Pd/K/Co-oxide catalyst for water gas shift
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Various Co3O4 catalysts were investigated for the water gas shift (WGS) reaction for hydrogen production. Although the catalyst supporting only palladium (Pd/Co3O4) showed low catalytic activity and higher selec
- Kono, Eugene,Tamura, Sakurako,Yamamuro, Keisuke,Ogo, Shuhei,Sekine, Yasushi
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p. 247 - 254
(2015/05/05)
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- The effect of water on the heterogeneously catalyzed selective oxidation of acrolein: An isotope study
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The effect of water on the selective gas phase oxidation of acrolein to acrylic acid on a Mo/V/W mixed oxide catalyst was studied by performing steady-state isotopic transient kinetic analysis experiments with H 218O. Experiments were performed in the temperature range of 90-345C at ambient pressure. It could be shown that acrolein exchanges its carbonylic oxygen with oxygen from water even at low temperatures (200C), the oxygen atoms of the water molecules incorporate into all oxidation products such as acrylic acid, carbon monoxide, and carbon dioxide.
- Petzold, Tina,Blickhan, Nina,Drochner, Alfons,Vogel, Herbert
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p. 2053 - 2058
(2014/08/05)
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- Quantification of the 248 nm photolysis products of HCNO (fulminic Acid)
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IR diode laser spectroscopy was used to detect the products of HCNO (fulminic acid) photolysis at 248 nm. Five product channels are energetically possible at this photolysis wavelength: O + HCN, H + (NCO), CN + OH, CO + NH, and HNCO. In some experiments, isotopically labeled 18O2, 15N18O and C2D6 reagents were included into the photolysis mixture in order to suppress and/or isotopically label possible secondary reactions. HCN, OC18O, C18O, NCO, DCN, and NH molecules were detected upon laser photolysis of HCNO/reagents/buffer gas mixtures. Analysis of the yields of product molecules leads to the following photolysis quantum yields: 1a (O + HCN) = 0.39 ± 0.07, 1b (H + (NCO)) = 0.21 ± 0.04, 1c (CN + OH) = 0.16 ± 0.04, 1d (CN + NH(a1Δ)) = 0.19 0.03, and 1e (HNCO) = 0.05 ± 0.02, respectively. The uncertainties include both random errors (1σ) and consideration of major sources of systematic error. In conjunction with the photolysis experiment, the H + HCNO reaction was investigated. Experimental data demonstrate that this reaction is very slow and does not contribute significantly to the secondary chemistry.
- Feng, Wenhui,Hershberger, John F.
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p. 829 - 837
(2014/03/21)
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- Kinetic study of heterogeneous oxygen-exchange reactions and bulk self-diffusion of oxygen
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Apparent activation energies are determined for oxygen-isotope exchange reactions between O2, CO, or NO and preoxidized or prereduced CaO surfaces. Oxygen exchange between N16O or C16O and isotope labeled Ca18O surfaces produced an apparent activation energy of 2 kcal/mol. Similar values are obtained for single-isotope-exchange between 18O18O and prereduced Ca16O surfaces. Apparent activation energies of 15-18 kcal/mol are found for single and double exchange between 18O18O and preoxidized Ca16O surfaces, as well as for double exchange between 18O18O and prereduced Ca16O surfaces. The low apparent activation energies are believed to result from adsorbed intermediates, whereas the high values may involve the formation of a singlet O2 transient. It is shown that eventually the self-diffusion of oxygen ions in the bulk becomes the rate-determining step in the isotope-exchange reaction. Apparent activation energies are determined, and the values are found to depend on surface treatment, (i.e., 44 kcal/mol under reducing and 78 kcal/mol under oxidizing conditions). The involvement of oxygen vacancies under reducing conditions is discussed.
- Acke, Filip,Panas, Itai
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p. 5158 - 5164
(2007/10/03)
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- Photochemical Oxidation of Carbonyl Sulfide and Carbon Disulfide in Solid O2 at 15 K and the Molecular Complexes of the Photoproducts
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The photooxidation of OCS and CS2 in solid O2 at 15 K by UV light (λ a more complex product distribution.Probable precursor mechanisms are examined.The IR spectra of SO2, SO3, OCS, and CO molecular complexes are identified, and some of their structural features are examined.The photooxidation is not driven to completion to the thermochemically most stable set of products.
- Tso, Tai-Ly,Lee, Edward K. C.
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p. 2781 - 2787
(2007/10/02)
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- The Photochemical Water-gas Shift Reaction Catalysed by Bis(2,2'-bipyridyl)(carbonyl)chlororuthenium(II) Chloride
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Cl are shown to be active catalytic species for the water-gas shift reaction under mild conditions (1-3 atm CO, 100-160 deg C) and under illumination with white light.Turnover numbers of up to 20 1/h are observed.Stoicheiometric reactions, including labelling studies, shown that CO2 is produced thermally, whilst H2 is produced in a photochemical step.Mechanistic and kinetic data are presented for the catalytic reaction and they show that the reaction has a mechanism similar to those previously reported for the water-gas shift reaction and it does not involve formate decomposition.The rate-determaning step at all pH is photochemical loss of H2 from (1+) and different activation energies at high and low pH are attributed to different contributions from pre-equilibria involving attack of OH(1-) on co-ordinated CO (dominant at low pH) or protonation of (dominant at high pH).Experiments at high conversin show that at 140 deg C CO can be completely converted to products.Attempts to catalyse related reactions using unsaturated substrates are also described.
- Choudhury, Dibakar,Cole-Hamilton, David J.
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p. 1885 - 1894
(2007/10/02)
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