766-76-7Relevant academic research and scientific papers
Reactivity of Superoxide Ion with Ethyl Pyruvate, α-Diketones, and Benzil in Dimethylformamide
Sawyer, Donald T.,Stamp John J.,Menton, Kathleen A.
, p. 3733 - 3736 (1983)
The dominant net reaction of O2(1-) radical with α-dicarbonyls such as ethyl pyruvate, 2,3-butanedione, and 2,3-pentanedione is proton abstraction from their enol tautomer.The rate-limiting step is first order for each reactant, the net products are enolate plus O2 and H2O2, and the second-order rate constants (k) are the same, within experimental error, for the three substrates (k = (4+/-1) x 103 M-1 s-1).For the reaction of benzil (an α-dicarbonyl that cannot enolize) with O2(1-) radical the rate-limiting step is first order for each reactant, and the second- order rate constant (k) is (2+/-1) x 103 M-1 s-1.The process appears to involve an initial nucleophilic addition by O2(1-) radical to carbonyl carbon, followed by a dioxetane closure on the other carbonyl carbon and reductive cleavage by a second O2(1-) radical to give two benzoate ions and O2.
Energetics of product formation during anaerobic degradation of phthalate isomers and benzoate
Kleerebezem, Robbert,Hulshoff Pol, Look W.,Lettinga, Gatze
, p. 273 - 282 (1999)
Methanogenic enrichment cultures grown on phthalate, isophthalate and terephthalate were incubated with the corresponding phthalate isomer on which they were grown, and a mixture of benzoate and the phthalate isomer. All cultures were incubated with bromoethanosulfonate to inactivate the methanogens in the mixed culture. Thus, product formation during fermentation of the aromatic substrates could be studied. It was found that reduction equivalents generated during oxidation of the aromatic substrates to acetate were incorporated in benzoate under formation of carboxycyclohexane. During fermentation of the phthalate isomers, small amounts of benzoate were detected, suggesting that the initial step in the anaerobic degradation of the phthalate isomers is decarboxylation to benzoate. Gibbs free energy analyses indicated that during degradation of the phthalate isomers, benzoate, carboxycyclohexane, acetate and molecular hydrogen accumulated in such amounts that both the reduction and oxidation of benzoate yielded a constant and comparable amount of energy of approximately 30 kJ mol-1. Based on these observations it is suggested that within narrow energetic limits, oxidation and reduction of benzoate may proceed simultaneously. Whether this is controlled by the Gibbs free energy change for carboxycyclohexane oxidation remains unclear. Copyright (C) 1999 Federation of European Microbiological Societies.
Molecular Engineering to Tune the Ligand Environment of Atomically Dispersed Nickel for Efficient Alcohol Electrochemical Oxidation
Liang, Zhifu,Jiang, Daochuan,Wang, Xiang,Shakouri, Mohsen,Zhang, Ting,Li, Zhongjun,Tang, Pengyi,Llorca, Jordi,Liu, Lijia,Yuan, Yupeng,Heggen, Marc,Dunin-Borkowski, Rafal E.,Morante, Joan R.,Cabot, Andreu,Arbiol, Jordi
, (2021)
Atomically dispersed metals maximize the number of catalytic sites and enhance their activity. However, their challenging synthesis and characterization strongly complicates their optimization. Here, the aim is to demonstrate that tuning the electronic environment of atomically dispersed metal catalysts through the modification of their edge coordination is an effective strategy to maximize their performance. This article focuses on optimizing nickel-based electrocatalysts toward alcohol electrooxidation in alkaline solution. A new organic framework with atomically dispersed nickel is first developed. The coordination environment of nickel within this framework is modified through the addition of carbonyl (CO) groups. The authors then demonstrate that such nickel-based organic frameworks, combined with carbon nanotubes, exhibit outstanding catalytic activity and durability toward the oxidation of methanol (CH3OH), ethanol (CH3CH2OH), and benzyl alcohol (C6H5CH2OH); the smaller molecule exhibits higher catalytic performance. These outstanding electrocatalytic activities for alcohol electrooxidation are attributed to the presence of the carbonyl group in the ligand chemical environment, which enhances the adsorption for alcohol, as revealed by density functional theory calculations. The work not only introduces a new atomically dispersed Ni-based catalyst, but also demonstrates a new strategy for designing and engineering high-performance catalysts through the tuning of their chemical environment.
A Green-LED Driven Source of Hydrated Electrons Characterized from Microseconds to Hours and Applied to Cross-Couplings
Naumann, Robert,Goez, Martin
, p. 9833 - 9840 (2018)
We present a novel photoredox catalytic system that delivers synthetically usable concentrations of hydrated electrons when illuminated with a green light-emitting diode (LED). The catalyst is a ruthenium complex protected by an anionic micelle, and the urate dianion serves as a sacrificial donor confined to the aqueous bulk. By virtue of its chemical properties, this donor not only suppresses charge recombination that would limit the electron yield, but also enables this system to perform cross-couplings through the action of hydrated electrons, the first examples of which are reported here. We have investigated the kinetics of all the steps involving the electron and its direct precursor in a comparative study by means of laser flash photolysis and by monitoring product formation during LED photolysis. Despite the differences in timescales, each approach on its own already gives a complete picture of the reaction over a temporal range spanning ten orders of magnitude. Discrepancies between the kinetic parameters obtained with the two complementary techniques can be rationalized with the slow secondary chemistry of the system; they reveal that the product-based method provides a more accurate description because it also responds to the changes of the system composition during a synthesis; hence, they demonstrate that in complex systems the timescale of the experimental observation should be matched to that of the actual application.
Time-resolved RNA SHAPE chemistry
Mortimer, Stefanie A.,Weeks, Kevin M.
, p. 16178 - 16180 (2008)
Selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry yields quantitative RNA secondary and tertiary structure information at single nucleotide resolution. SHAPE takes advantage of the discovery that the nucleophilic reactivity of the ribose 2′-hydroxyl group is modulated by local nucleotide flexibility in the RNA backbone. Flexible nucleotides are reactive toward hydroxyl-selective electrophiles, whereas constrained nucleotides are unreactive. Initial versions of SHAPE chemistry, which employ isatoic anhydride derivatives that react on the minute time scale, are emerging as the ideal technology for monitoring equilibrium structures of RNA in a wide variety of biological environments. Here, we extend SHAPE chemistry to a benzoyl cyanide scaffold to make possible facile time-resolved kinetic studies of RNA in～1 s snapshots. We then use SHAPE chemistry to follow the time-dependent folding of an RNase P specificity domain RNA. Tertiary interactions form in two distinct steps with local tertiary contacts forming an order of magnitude faster than long-range interactions. Rate-determining tertiary folding requires minutes despite that no non-native interactions must be disrupted to form the native structure. Instead, overall folding is limited by simultaneous formation of interactions～55 A distant in the RNA. Time-resolved SHAPE holds broad potential for understanding structural biogenesis and the conformational interconversions essential to the functions of complex RNA molecules at single nucleotide resolution. Copyright
Indirect detection of intermediate in decarboxylation reaction of phenylglyoxylic acid by hyperpolarized13C NMR
Kim, Jiwon,Kim, Yaewon,Luu, Quy Son,Kim, Jihyun,Qi, Chang,Hilty, Christian,Lee, Youngbok
, p. 15000 - 15003 (2020/12/22)
The decarboxylation reaction of phenylglyoxylic acid with hydrogen peroxide is studied by real-Time hyperpolarized carbon-13 nuclear magnetic resonance (13C NMR) spectroscopy at room temperature. A non-observable reaction intermediate is identified using blind selective saturation pulses in the expected chemical shift range, thereby revealing information on the reaction mechanism. This journal is
Characterizing Cation Chemistry for Anion Exchange Membranes - A Product Study of Benzylimidazolium Salt Decompositions in the Base
Pellerite, Mark J.,Kaplun, Marina M.,Webb, Robert J.
, p. 15486 - 15497 (2019/11/19)
Imidazolium functionality has played a prominent role in research on anion exchange membranes for use in alkaline electrochemical devices. Base stability and degradation of these materials has been much studied, but in many instances, product pathways have not been thoroughly delineated. We report an NMR study of base-induced decomposition products from three benzylimidazolium salts bearing varying extents of methyl substitution on the imidazolium ring. The major products are consistent with a hydrolytic ring fragmentation pathway as the principal mode of decomposition. We observe several new products not previously reported in the literature on imidazolium salt degradation, including benzilic acid rearrangement products formally derived from intermediate 1,2-dicarbonyl compounds or their equivalents. However, the overall reactions are complex, the yields of observed products do not account for all consumed starting materials, and mechanistic ambiguities remain.
Oxidation kinetics of ferrocene derivatives with dibenzoyl peroxide
Halstead, Joshua M.,Abu-Saleh, Refaat,Schildcrout, Steven M.,Masnovi, John
, p. 39 - 46 (2018/11/10)
Chemical oxidation of ferrocene and related derivatives by dibenzoyl peroxide in acetonitrile solution produces ferrocenium and benzoic acid after acidification. The rate law is first order in oxidant and in reductant. Steric effects and activation parameters are consistent with a rate-controlling outer-sphere single-electron transfer (ET) step, and reorganization energies are obtained using Marcus theory with B3LYP calculations. Energetics, optimized structures, and solvent effects indicate that rate is affected more by anion than cation solvation and that oxidation of decamethylferrocene by 3-chloroperoxybenzoic acid does not occur by ET.
Unexpected resistance to base-catalyzed hydrolysis of nitrogen pyramidal amides based on the 7-azabicyclic[2.2.1]heptane scaffold
De Velasco, Diego Antonio Ocampo Gutiérrez,Su, Aoze,Zhai, Luhan,Kinoshita, Satowa,Otani, Yuko,Ohwada, Tomohiko
, (2018/09/26)
Non-planar amides are usually transitional structures, that are involved in amide bond rotation and inversion of the nitrogen atom, but some ground-minimum non-planar amides have been reported. Non-planar amides are generally sensitive to water or other n
Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light-Emitting Diode
Naumann, Robert,Lehmann, Florian,Goez, Martin
, p. 13259 - 13269 (2018/09/10)
We have explored alkyl substitution of the ligands as a means to improve the performance of the title complexes in photoredox catalytic systems that produce synthetically useable amounts of hydrated electrons through photon pooling. Despite generating a super-reductant, these electron sources only consume the bioavailable ascorbate and are driven by a green light-emitting diode (LED). The substitutions influence the catalyst activity through the interplay of the quenching parameters, the recombination rate of the reduced catalyst OER and the ascorbyl radical across the micelle-water interface, and the quantum yield of OER photoionization. Laser flash photolysis yields comprehensive information on all these processes and allows quantitative predictions of the activity observed in LED kinetics, but the latter method provides the only access to the catalyst stability under illumination on the timescale of the syntheses. The homoleptic complex with dimethylbipyridine ligands emerges as the optimum that combines an activity twice as high with an undiminished stability in relation to the parent compound. With this complex, we have effected dehalogenations of alkyl and aryl chlorides and fluorides, hydrogenations of carbon–carbon double bonds, and self- as well as cross-coupling reactions. All the substrates employed are impervious to ordinary photoredox catalysts but present no problems to the hydrated electron as a super-reductant. A particularly attractive application is selective deuteration with high isotopic purity, which is achieved simply by using heavy water as the solvent.
