- Radiation Chemical Studies of Nickel-Glycine. Hydrogen Abstraction by OH Radicals and Oxidation by Br2-1
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Reactions of hydroxyl radicals with Ni(II)-glycine complexes were studied by pulse radiolysis and by product analysis.Radiolytic degradation of the complexes in N2O-saturated solutions leads to the formation of carbonyl compounds.The nature and the yield of these products indicate that the transient formed by reaction of OH with the complex undergoes disproportionation.The optical absorption spectrum of this transient exhibits a maximum below 250 nm, which is similar to that observed with glycine alone.The reaction of Br2- with the complex is found to be too slow to be observed by pulse radiolysis.However, the reaction occurs in steady-state radiolysis and yield products different from those observed with OH.Specifically, the yield of formaldehyde is appreciably higher in the presence of Br-.It is concluded that Br2- oxidizes the metal center of the Ni(II)-glycine complex to Ni(III), whereas OH reacts by hydrogen abstraction to form Ni(II)-coordinated glycine radical.
- Bhattacharyya, S.N,Neta, P.
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- Formation of Two-Carbon Acids from Carbon Dioxide by Photoreduction on Cadmium Sulphide
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Aqueous solutions of CO2 containing tetramethylammonium chloride were photolysed with visible light in the presence of colloidal CdS to yield glyoxylic acid as well as formic and acetic and CH2O.
- Eggins, Brian R.,Irvine, John T. S.,Murphy, Eileen P.,Grimshaw, James
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- Combination of Sodium Dodecylsulfate and 2,2′-Bipyridine for Hundred Fold Rate Enhancement of Chromium(VI) Oxidation of Malonic Acid at Room Temperature: A Greener Approach
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Chromic acid oxidation of malonic acid in aqueous media has been investigated spectrophotometrically at 303?K. The product glyoxylic acid has been characterized by 13C-NMR and FTIR spectroscopy. Three representative N-heteroaromatic nitrogen base promoters, 2-picolinic acid, 2,2′-bipyridine (bpy) and 1,10-phenanthroline, in combination with the anionic surfactant sodium dodecylsulfate (SDS) enhanced the rate of the oxidation reaction compared to the unpromoted reaction.?2,2′-Bipyridine produced the maximum rate enhancement of the three promoters used. The mechanism of the reaction has been proposed with the help of kinetic results and spectroscopic studies. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. The SDS and bpy combination is suitable for malonic acid oxidation.
- Malik, Susanta,Mondal, Monohar Hossain,Ghosh, Aniruddha,De, Sourav,Mahali, Kalachand,Bhattacharyya, Shuvendu Sekhar,Saha, Bidyut
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- An Unusual Oxidative Ring Transformation of Purine to Imidazo[1,5-c] imidazole
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(Equation presented) Reevaluation of products derived from 3, 9-dimethyluric acid in a chlorination-reductive dechlorinaton sequence has demonstrated unequivocally that they are not purines. Spectroscopic and degradative evidence, in conjunction with position-labeling NMR studies, revealed an unprecedented oxidative ring transformation pathway involving the key purine-to-imidazo[1,5-c]imidazole rearrangement.
- Poje, Nevenka,Poje, Mirko
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- Formation of Glyoxylic Acid by Oxidative Dehydrogenation of Glycolic Acid
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Iron phosphates with a P/Fe atomic ratio of 1.2 were found to be effective as catalysts for a vapor-phase oxidative dehydrogenation of glycolic acid to glyoxylic acid.The effects of the reaction variables on the conversion and selectivity were studied.The optimum reaction temperature was around 240 deg C and the optimum feed rate of oxygen was in the range of 10 to 25 mmol h-1 when the feed rate of glycolic acid was 12.3 mmol h-1.The reaction was not affected by a variation in the feed rate of water vapor in the range of 86 to 480 mmol h-1.The selectivity to glyoxylic acid remained unchanged at 74 molpercent with an increase in the conversion of glycolic acid up to 70percent; the highest yield of glyoxylic acid was 56.5 molpercent at the conversion of 80percent.
- Ai, Mamoru,Ohdan, Kyoji
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- Mechanistic investigation of the oxidative cleavage of the carbon-carbon double bond in α,β-Unsaturated compounds by hexachloroiridate(iv) in acetate buffer
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The hexachloroiridate(IV) oxidation of α,β-unsaturated compounds such as acrylic acid, acrylamide, and acrylonitrile (CH2=CHX; X = -COOH, -CONH2, and -CN) was carried out in NaOAc-AcOH buffer medium. The reaction follows complex kinetics, being first order in [IrIV] and complex order in [CH2=CHX]. H+ ion has no effect on the reaction rate in the pH range 3.42-4.63. The pseudo-first-order rate constant decreases with a decrease in the dielectric constant and with a decrease of ionic strength of the medium. The oxidation rate follows the sequence: acrylonitrile > acrylamide > acrylic acid. A mechanism is proposed involving the formation of an unstable intermediate complex between the substrate and the oxidant which is transformed to the radical cation in a slow rate-determining step with the concomitant reduction of Ir(IV) to Ir(III). The radical cation subsequently decomposes to the aldehyde that appears as the ultimate product of the carbon-carbon double bond cleavage. The major product of oxidation was identified as HCHO by 1H NMR. Activation parameters for the slow rate-determining step and thermodynamic parameters associated with the equilibrium step of the proposed mechanism have been evaluated. The enthalpy of activation is linearly related to the entropy of activation, and this linear relationship confirms that the oxidation of all the α,β-unsaturated compounds follows a common mechanism.
- Pal, Biswajit
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- Novel alcohol oxidase with glycolate oxidase activity from Ochrobactrum sp. AIU 033
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We revealed that Ochrobactrum sp. AIU 033, which accumulated a high concentration of glyoxylate from glycolate, produced an enzyme catalyzing oxidation of glycolate to glyoxylate. The enzyme further oxidized lactate and primary alcohols (C2-C10), but did not oxidize glyoxylate, ethylene glycol, glycerol, or methanol. The Km value for glycolate (167 mM) was higher than that for primary alcohols. The glycolate oxidase activity was optimum at pH 5.5, and more than 80% of the enzyme activity remained in the pH range from 5.5 to 6.5 and at below 35 °C. The enzyme had a molecular mass of 130 kDa and was composed of an α2β2 structure, in which the α subunit was 52 kDa and the β subunit was 14 kDa. The enzyme was a flavoprotein and contained two iron atoms. The N-terminal sequences of the 52 kDa subunit and 14 kDa subunit had high similarity to those of putative glucose-methanol-choline oxidoreductases and putative 2-keto-gluconate dehydrogenase. These findings implied that the enzyme was a novel type of alcohol oxidase exhibiting glycolate oxidase activity. The enzyme accumulated glyoxylate with time, but oxalate, which is the oxidation product of glyoxylate, was not detected. This result also indicated that the enzyme catalyzed the formation of glyoxylate in the resting cell-reaction and thus could be useful in the enzymatic production of glyoxylate.
- Yamada, Miwa,Higashiyama, Takanori,Kishino, Shigenobu,Kataoka, Michihiko,Ogawa, Jun,Shimizu, Sakayu,Isobe, Kimiyasu
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- Selective Oxidation of Glyoxal to Glyoxalic Acid by Air over Mesoporous Silica Supported Pd Catalysts
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Abstract: A series of mesoporous silica (KIT-6, MCM-41 and SBA-15) supported Pd catalysts were successfully synthesized and applied for selective oxidation of glyoxal. All of these catalysts exhibited significantly higher activity than commercial Pd/C. Among them, Pd/KIT-6 exhibited the best activity and selectivity with 41.3% glyoxal conversion and 57.0% selectivity to glyoxalic acid. The better performance of Pd/KIT-6 was attributed to its three-dimensional mesoporous structure. The three-dimensional mesoporous structure of KIT-6 could enhance Pd dispersion, providing sufficient accessible active sites which improved the conversion of glyoxal. Meanwhile, the better mass transfer capability of Pd/KIT-6 allowed glyoxalic acid to leave the catalyst easily, reducing the probability of over-oxidation. The ratio of kI (rate constant of initial oxidation reaction) to kII (rate constant of over-oxidation) was compared among three catalysts. The kI/kII of Pd/KIT-6 (0.50) was higher than that of Pd/MCM-41 (0.39) and Pd/SBA-15 (0.34), which reflected its best selectivity from kinetic aspect. Graphical Abstract: [Figure not available: see fulltext.]
- Liu, Junchi,Qin, Feng,Huang, Zhen,Huang, Liang,Liao, Zhenan,Xu, Hualong,Shen, Wei
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- Aluminum(III) triflate-catalyzed selective oxidation of glycerol to formic acid with hydrogen peroxide
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Glycerol is a by-product of biodiesel production and is an important readily available platform chemical. Valorization of glycerol into value-added chemicals has gained immense attention. Herein, we carried out the conversion of glycerol to formic acid and glycolic acid using H2O2 as an oxidant and metal (III) triflate-based catalytic systems. Aluminum(III) triflate was found to be the most efficient catalyst for the selective oxidation of glycerol to formic acid. A correlation between the catalytic activity of the metal cations and their hydrolysis constants (Kh) and water exchange rate constants was observed. At 70 °C, a formic acid yield of up to 72% could be attained within 12 h. The catalyst could be recycled at least five times with a high conversion rate, and hence can also be used for the selective oxidation of other biomass platform molecules. Reaction kinetics and 1H NMR studies showed that the oxidation of glycerol (to formic acid) involved glycerol hydrolysis pathways with glyceric acid and glycolic acid as the main intermediate products. Both the [Al(OH)x]n+ Lewis acid species and CF3SO3H Br?nsted acid, which were generated by the in-situ hydrolysis of Al(OTf)3, were responsible for glycerol conversion. The easy availability, high efficiency, and good recyclability of Al(OTf)3 render it suitable for the selective oxidation of glycerol to high value-added products.
- Kong, Kang,Li, Difan,Ma, Wenbao,Zhou, Qingqing,Tang, Guoping,Hou, Zhenshan
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- Stereochemistry of the decarboxylation of glyoxylic acid by yeast pyruvate decarboxylase
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Tritiated glyoxylic acid was incubated with pyruvate decarboxylase. The hydroxymethylthiamine diphosphate formed was ozonolysed to give tritiated glycolic acid, the absolute configuration of which was investigated by analysis using glycolate oxidase. The tritiated glycolic acid proved to be racemic. The implications of this result are discussed in relation to models for the mechanism of pyruvate decarboxylase.
- Vegad, Hiran,Lobell, Mario,Bornemann, Stephen,Crout, David H.G.
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- The Autoxidation of 2,3-Dihydroxy-2-propenal (Triose Reductone). The Effects of the pH on the Rate Constants
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The autoxidation of 2,3-dihydroxy-2-propenal (triose reductone) was investigated between pH 2.83 and 13.91 in the presence of disodium dihydrogen ethylenediaminetetraacetate (EDTA 2NA).The reaction obeyed the first-order rate law with respect to the triose reductone and the zeroth-order rate law with respect to oxygen when the oxygen concentration was higher than 0.246 mM (1 mM = 10-3 mol dm-3) at 30 deg C.The pH dependence of the reaction rates showed that the reaction rates are governed by the acid-base equilibrium of triose reductone.The rate constants for neutral and singly- and doubly-charged anions of triose reductone at 30 deg C were (3.6 +/- 0.1) * 10-6, (7 +/- 1) * 10-5, and (1.8 +/- 0.1) * 10-2 s-1 respectively.The hydrogen peroxide produced as a result of the triose reductone oxidation was also found to oxidize triose reductone.
- Abe, Yasuo,Horii, Hideo,Taniguchi, Setsuo,Kamai, Kazuo,Takagi, Masanosuke
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- Stoichiometric Fingerprinting as an Aid in Understanding Complex Reactions: The Oxidation of Malonic Acid by Cerium(IV)
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The stoichiometry of the Ce(IV) oxidation of malonic acid (MA) under aerobic and anaerobic conditions was investigated.The Ce(IV)/MA consumption ratio is found to vary from about 3.5 to 7, depending nonlinearly on the initial concentration of malonic acid as well as dissolved oxygen.The observed data can be quantitatively explained by a model that employs the characteristic structure of branching pathways in the overall mechanism and does not require the exact knowledge of the rate constants.It is concluded that a systematic study of consumption ratios provides an important aid for elucidating mechanisms of complex reactions.
- Neumann, Bettina,Steinbock, Oliver,Mueller, Stefan C.,Dalal, Nar S.
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- Facilitated series electrochemical hydrogenation of oxalic acid to glycolic acid using TiO2 nanotubes
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In this study, the electrochemical reduction of oxalic acid (OX) was performed at electrodes made of TiO2 nanotubes (TNTs) in an aqueous medium under potentiostatic control in a two-compartment cell. The competing H2 evolution was almost non-existent at an applied potential of ?1.0 V vs Ag/AgCl. Thus, complete conversion of OX was achieved in high chemical (95%) and Faradaic (67%) yields. The selectivity of glycolic acid (GC) formation over that of glyoxylic acid (GO) is controlled by the length of the TNTs. A high selectivity (GC/GO ≈ 10) was obtained (glycolic acid/glyoxylic acid ≈ 10). The physical properties of the TNTs, such as length, uniformity, and mechanical strength, were controlled by varying the anodization time and the electrolyte composition.
- Im, Sunmi,Park, Yiseul,Saad, Sarwar
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- Preparation method for producing glyoxylic acid through catalytic oxidation of composite solid acid
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The invention provides a preparation method for producing glyoxylic acid through catalytic oxidation of composite solid acid, and belongs to the field of chemical production, and the preparation method for producing glyoxylic acid through catalytic oxidation of composite solid acid comprises the specific steps of raw material preparation, oxidation extraction treatment, oxidation extraction powderpreparation and processing operation, glyoxylic acid processing and filtering treatment and transportation. According to the method, a cocatalyst compound solid acid catalytic oxidation solution is added, so that the yield of glyoxylic acid is increased; the operation environment is improved, the defects of easy environmental pollution and easy equipment corrosion are avoided, the product qualityis stable, and the method is suitable for industrial production; and through multi-layer filtration, the production efficiency of glyoxylic acid can be ensured, the production purity of glyoxylic acid is ensured, the use effect is improved, and the method is simple to store and easy to master.
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Paragraph 0027-0032
(2021/03/18)
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- Method for preparing glyoxylic acid through catalytic oxidation reaction extraction of glyoxal
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The invention discloses a method for preparing glyoxylic acid through glyoxal catalytic oxidation reaction extraction, and belongs to the field of catalysts and reaction. The method specifically includes the steps of preparing structure-and-performance-adjustable Pd/SiO2 catalyst with SiO2 wrapping Pd particles through a micro-emulsion method, and preparing glyoxylic acid through catalytic glyoxalair oxidation extraction reaction with n-caprylic alcohol as a diluting agent and trioctylamine as an extracting agent. The reaction is conducted at the pH value of 7.3-7.7 and the temperature of 35-50 DEG C, the conversion rate reaches 76%, the glyoxylic acid yield reaches 60%, and the product purity is obviously higher than that of a traditional industrial production process.
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Paragraph 0030-0037
(2021/01/24)
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- Electrochemical oxidation of amoxicillin on carbon nanotubes and carbon nanotube supported metal modified electrodes
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The electrolysis of amoxicillin (AMX) was carried out on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in 0.1 M NaOH, 0.1 M NaCl and 0.1 M Na2CO3/NaHCO3 buffer (pH 10) media with the aim of studying the significance of two factors, electrode material and pH, on the oxidative degradation and mineralization of AMX. For this purpose, the electrolysis products were identified by HPLC-MS and GC–MS, and quantified by HPLC-UV-RID and IC. The highest carbon mineralization efficiency, corresponding to 30% of the oxidized AMX, was found for Pt/CNT modified electrode in carbonate buffer medium. Regarding to the AMX conversion, the results show that the effect of pH is higher than that of the electrode material. Principal component analysis allowed to determine the experimental parameters vs. product distribution relationship and to elucidate the oxidation pathways for the studied electrodes. The results show that the hydroxylation of the aromatic ring and the nitrogen atom play an important role on the efficient degradation of AMX.
- Ferreira, Marta,Kuzniarska-Biernacka, Iwona,Fonseca, António M.,Neves, Isabel C.,Soares, Olívia S.G.P.,Pereira, Manuel F.R.,Figueiredo, José L.,Parpot, Pier
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p. 322 - 331
(2019/07/10)
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- A METHOD OF OXIDIZING GLYCOLALDEHYDE USING NITRIC ACID
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The present invention relates to a method of synthesizing at least one organic acid comprising oxidizing glycolaldehyde with nitric acid in the presence of a solvent. Advantageously, it is an industrially applicable process, which prepares organic acid, notably glycolic acid and/or glyoxylic acid in a high yield based on bio-based feedstocks.
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Page/Page column 7
(2020/12/29)
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- Method for preparing allantoin using titanium dioxide-based composite solid catalyst
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The invention provides a method for preparing allantoin using a titanium dioxide-based composite solid catalyst. The preparation method comprises the following steps of (1) mixing tetrabutyl titanate,graphene, dimethyl formamide and ethanol to form a solution A; (2) mixing water, ethanol and acetic acid to form a solution B; (3) mixing copper salt, zinc salt, silver salt, water and ethanol to form a solution C; (4) simultaneously adding the solution B and the solution C into the solution A, standing, drying and grinding, so as to obtain a powdery material; (5) calcining the powdery material,so as to obtain the solid catalyst; (6) soaking the solid catalyst, zinc chloride and niobium pentachloride into hydrochloric acid, and then drying to obtain a titanium dioxide-based complex/lewis acid composition; (7) performing oxidizing reaction on glyoxal and nitric acid to produce glyoxalic acid, and performing condensation reaction on the glyoxalic acid, urea and composition, so as to obtainthe allantoin. The method can reach excellent yield.
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Paragraph 0037-0039
(2018/12/14)
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- Domino Synthesis of α,β-Unsaturated γ-Lactams by Stereoselective Amination of α-Tertiary Allylic Alcohols
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Tertiary allylic alcohols equipped with a carboxyl group can be smoothly aminated under ambient conditions by a conceptually new and stereoselective protocol under palladium catalysis. The in situ formed Z-configured γ-amino acid cyclizes to afford an α,β-unsaturated γ-lactam, releasing water as the only byproduct. This practical catalytic transformation highlights the use of a carboxyl group acting as an activating and stereodirecting functional group to provide a wide series of pharma-relevant building blocks. Various control reactions support the crucial role of the carboxyl group in the substrate to mediate these transformations.
- Xie, Jianing,Xue, Sijing,Escudero-Adán, Eduardo C.,Kleij, Arjan W.
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supporting information
p. 16727 - 16731
(2018/11/23)
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- Exceptionally rapid oxime and hydrazone formation promoted by catalytic amine buffers with low toxicity
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Hydrazone and oxime bond formation between α-nucleophiles (e.g. hydrazines, alkoxy-amines) and carbonyl compounds (aldehydes and ketones) is convenient and is widely applied in multiple fields of research. While the reactants are simple, a substantial drawback is the relatively slow reaction at neutral pH. Here we describe a novel molecular strategy for accelerating these reactions, using bifunctional buffer compounds that not only control pH but also catalyze the reaction. The buffers can be employed at pH 5-9 (5-50 mM) and accelerate reactions by several orders of magnitude, yielding second-order rate constants of >10 M-1 s-1. Effective bifunctional amines include 2-(aminomethyl)imidazoles and N,N-dimethylethylenediamine. Unlike previous diaminobenzene catalysts, the new buffer amines are found to have low toxicity to human cells, and can be used to promote reactions in cellular applications.
- Larsen, Dennis,Kietrys, Anna M.,Clark, Spencer A.,Park, Hyun Shin,Ekebergh, Andreas,Kool, Eric T.
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p. 5252 - 5259
(2018/06/21)
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- Photoelectroreduction of Building-Block Chemicals
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Conventional photoelectrochemical cells utilize solar energy to drive the chemical conversion of water or CO2 into useful chemical fuels. Such processes are confronted with general challenges, including the low intrinsic activities and inconvenient storage and transportation of their gaseous products. A photoelectrochemical approach is proposed to drive the reductive production of industrial building-block chemicals and demonstrate that succinic acid and glyoxylic acid can be readily synthesized on Si nanowire array photocathodes free of any cocatalyst and at room temperature. These photocathodes exhibit a positive onset potential, large saturation photocurrent density, high reaction selectivity, and excellent operation durability. They capitalize on the large photovoltage generated from the semiconductor/electrolyte junction to partially offset the required external bias, and thereby make this photoelectrosynthetic approach significantly more sustainable compared to traditional electrosynthesis.
- Chen, Fengjiao,Cui, Wei,Zhang, Jie,Wang, Yeyun,Zhou, Junhua,Hu, Yongpan,Li, Yanguang,Lee, Shuit-Tong
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p. 7181 - 7185
(2017/06/13)
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- Synthetic method of allantoin
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The invention provides a synthetic method of allantoin. The synthetic method of the allantoin comprises the following steps of slowly adding hydrogen peroxide into a homogeneous reactor filled with an oxalaldehyde solution, adding a catalyst, and reacting for 90 min to obtain an intermediate product a glyoxylic acid solution, wherein the molar ratio of the hydrogen peroxide and the oxalaldehyde is 0.5 to 0.8:1, and the dosage of the catalyst is 1.6 to 2.8 percent; then adding urea and the catalyst into the glyoxylic acid solution, reacting for 90min at the temperature of 60 DEG C, and after completing reaction, cooling crystallizing, standing, filtering, washing, drying and smashing the reaction product to obtain the target product allantoin. According to the synthetic method of the allantoin provided by the invention, phosphotungstic acid is adopted as the catalyst so as to directly synthesize the allantoin by reaction under a moderate condition, so that the method is simple and efficient, and solves the problem of blasting boiling caused by jump of temperature during an oxidization operation process, the reaction time is shortened, the enterprise production cost is reduced, the yield of the glyoxylic acid and the allantoin is improved, the catalyst used in reaction can be recycled and recovered, and the synthetic method of the allantoin has a very high popularization value.
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Paragraph 0011; 0012; 0013; 014; 0015; 0016-0019
(2017/07/04)
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- Method for synthesizing glyoxylic acid by means of ozonizing maleic anhydride and mixed solvents
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The invention relates to a method for synthesizing glyoxylic acid by means of ozonizing maleic anhydride and mixed solvents, and belongs to the field of technologies for preparing glyoxylic acid. The method for synthesizing the glyoxylic acid by means of ozonizing the maleic anhydride and the mixed solvents is low in cost. The method includes steps of carrying out hydrolysis, ozone oxidation, reduction, reduced-pressure distillation, crystallization and the like on the inexpensive maleic anhydride in the mixed solvents to ultimately obtain glyoxylic acid solid. The method has the advantages that the glyoxylic acid solid with high purity can be directly obtained by the aid of the method, and products are high in quality and wide in application; the method is easy to implement and high in glyoxylic acid yield, the maleic anhydride can be converted into the glyoxylic acid at a low price, the method can be used for industrial large-scale production, and certain contribution can be made for solving the problem of situation of excessive maleic anhydride; optimization of the traditional processes for producing the glyoxylic acid and elimination of backward processes can be stimulated, environment-friendly oxidizing agents are adopted, and accordingly huge contribution can be made for environmental protection.
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Paragraph 0068; 0069; 0070; 0071; 0072; 0073; 0074-0121
(2017/03/25)
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- Glyoxalic acid and preparation method thereof
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The invention relates to a glyoxalic acid and a preparation method thereof. The technical scheme is as follows: the preparation method comprises the following steps: adding 100 parts by mass of 40 wt% glyoxal water solution, 10-20 parts by mass of 30 wt% hydrochloric acid solution and 10-25 parts by mass of 5-20 wt% nitrous acid water solution into a reaction kettle, heating to 45-55 DEG C while stirring, and adding 0.12-0.62 part by mass of sodium nitrate to obtain an initiation system; introducing oxygen into the initiation system with air stone at 55-65 DEG C under normal pressure while stirring, and meanwhile, uniformly and dropwisely adding 30-40 parts by mass of 30-45 wt% nitric acid into the initiation system; heating to 75-85 DEG C while stirring, and keeping the temperature for 1-2 hours; and adding 1-4 parts by mass of 30-45 wt% nitric acid, and continuing keeping the temperature for 1-2 hours, thereby obtaining the glyoxalic acid. The preparation method has the characteristics of low nitric acid consumption, low oxynitride discharge amount and high yield, and is beneficial to industrial production.
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Paragraph 0019-0022
(2017/03/22)
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- Method for preparing glyoxylic acid through carbon nanotube-loaded noble metal catalyst
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The invention relates to preparation of a carbon nanotube-loaded noble metal catalyst and a method for applying the carbon nanotube-loaded noble metal catalyst to clean synthesis of glyoxylic acid. The method comprises the following steps that polarization treatment is conducted on a carbon nanotube, wherein the carbon nanotube with a specific diameter is put into distilled water, the solution is stirred for 3-4 h, filtered, washed, dried and subjected to high-temperature reflux stirring together with mixed acid of nitric acid and sulfuric acid for 6-12 h, and the mixed solution is filtered, washed to be neutral and dried; nanometal particles are loaded in the carbon nanotube, the treated carbon nanotube is added into a metal precursor aqueous solution, after ultrasonic treatment is conducted for 4-8 h, stirring is conducted for 12 h, filtering and washing are conducted, reduction is conducted in a hydrazine hydrate solution or hydrogen atmosphere, and filtering, washing and vacuum drying are conducted; a chemical reaction of generating glyoxylic acid by oxidizing glyoxal through oxygen is catalyzed, the prepared carbon nanotube-loaded catalyst is added into the glyoxal aqueous solution, heating stirring is conducted, oxygen is introduced, the pH value of the system is controlled to be 6-8 through sodium hydroxide in the reaction process, and after the reaction is finished, filtering is conducted to obtain the glyoxylic acid solution.
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Paragraph 0019
(2017/06/10)
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- Combined EC-NMR and in Situ FTIR Spectroscopic Studies of Glycerol Electrooxidation on Pt/C, PtRu/C, and PtRh/C
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Glycerol, a byproduct of biodiesel production, is an industrial waste because of its excess yield. Electrooxidation of glycerol is a promising way to utilize glycerol - through harvesting electric energy as fuels in a fuel cell or hydrogen as sacrificial agent in electrolysis cell - while generating valuable chemicals. Here, we report a detailed mechanistic study of the glycerol electrooxidation reaction (GOR) on a series of Pt/C, PtxRuy/C, and PtxRhy/C nanocatalysts synthesized by NaBH4 reduction. The EC cyclic voltammetry characterization indicates that alloying Ru with Pt greatly enhanced the GOR activity, especially at low potential, but not as much with alloying Rh, as compared with Pt/C. In situ FTIR and 13C NMR spectroscopies were used to investigate the GOR mechanism at a molecular level. The results demonstrate that the selectivity of products depends on the type of catalysts and the oxidation potential. Although both PtRu/C and PtRh/C could accelerate the oxygen insertion reactions that led to higher selectivity of carboxylic acids, tartronic acid was more favored at high potential on the PtRh/C surface. (Chemical Equation Presented).
- Huang, Long,Sun, Jia-Yu,Cao, Shuo-Hui,Zhan, Mei,Ni, Zu-Rong,Sun, Hui-Jun,Chen, Zhong,Zhou, Zhi-You,Sorte, Eric G.,Tong, YuYe J.,Sun, Shi-Gang
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p. 7686 - 7695
(2016/11/17)
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- Catalyst-Free Singlet Oxygen-Promoted Decarboxylative Amidation of α-Keto Acids with Free Amines
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A novel catalyst-free decarboxylative amidation of α-keto acids with amines under mild conditions has been developed. Advantages of the new protocol include avoidance of metal catalysts and high levels of functional group tolerance. In addition, the reaction can be scaled up and shows high chemoselectivity. Preliminary mechanistic studies suggest that singlet oxygen, generated from oxygen under irradiation, is the key promoter for this catalyst-free transformation.
- Xu, Wen-Tao,Huang, Bei,Dai, Jian-Jun,Xu, Jun,Xu, Hua-Jian
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supporting information
p. 3114 - 3117
(2016/07/14)
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- Recombinant oxalate decarboxylase: Enhancement of a hybrid catalytic cascade for the complete electro-oxidation of glycerol
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The complete electro-oxidation of glycerol to CO2 is performed through an oxidation cascade using a hybrid catalytic system combining a recombinant enzyme, oxalate decarboxylase from Bacillus subtilis, and an organic oxidation catalyst, 4-amino-TEMPO. This system is capable of electrochemically oxidizing glycerol at a carbon electrode collecting all 14 electrons per molecule.
- Abdellaoui, Sofiene,Hickey, David P.,Stephens, Andrew R.,Minteer, Shelley D.
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p. 14330 - 14333
(2015/09/21)
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- Atomically mixed Fe-group nanoalloys: Catalyst design for the selective electrooxidation of ethylene glycol to oxalic acid
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We demonstrate electric power generation via the electrooxidation of ethylene glycol (EG) on a series of Fe-group nanoalloy (NA) catalysts in alkaline media. A series of Fe-group binary NA catalysts supported on carbon (FeCo/C, FeNi/C, and CoNi/C) and monometallic analogues (Fe/C, Co/C, and Ni/C) were synthesized. Catalytic activities and product distributions on the prepared Fe-group NA catalysts in the EG electrooxidation were investigated by cyclic voltammetry and chronoamperometry, and compared with those of the previously reported FeCoNi/C, which clarified the contributory factors of the metal components for the EG electrooxidation activity, C2 product selectivity, and catalyst durability. The Co-containing catalysts, such as Co/C, FeCo/C, and FeCoNi/C, exhibit relatively high catalytic activities for EG electrooxidation, whereas the catalytic performances of Ni-containing catalysts are relatively low. However, we found that the inclusion of Ni is a requisite for the prevention of rapid degradation due to surface modification of the catalyst. Notably, FeCoNi/C shows the highest selectivity for oxalic acid production without CO2 generation at 0.4 V vs. the reversible hydrogen electrode (RHE), resulting from the synergetic contribution of all of the component elements. Finally, we performed power generation using the direct EG alkaline fuel cell in the presence of the Fe-group catalysts. The power density obtained on each catalyst directly reflected the catalytic performances elucidated in the electrochemical experiments for the corresponding catalyst. The catalytic roles and alloying effects disclosed herein provide information on the design of highly efficient electrocatalysts containing Fe-group metals. This journal is
- Matsumoto, Takeshi,Sadakiyo, Masaaki,Ooi, Mei Lee,Yamamoto, Tomokazu,Matsumura, Syo,Kato, Kenichi,Takeguchi, Tatsuya,Ozawa, Nobuki,Kubo, Momoji,Yamauchi, Miho
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p. 11359 - 11366
(2015/05/20)
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- TUNABLE FLUORESCENCE USING CLEAVABLE LINKERS
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The invention relates to cleavable chemistry in general, and in particular, to tunable fluoresence using cleavable linkers present in fluorochrome-quencher conjugates.
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Paragraph 00112-00113
(2014/11/11)
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- Synthesis of glyoxalic acid using methyl dichloroacetate by microwave method
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Microwave irradiation was used to synthesize glyoxalic acid from methyl dichloroacetate. The effects of the irradiation time, reaction temperature, reactant ratio and different alkali on the yield of glyoxalic acid were studied and also compared with thos
- Niu, Qian,Luo, Xiong,Li, Shou-Gao,Meng, Ying,Li, Fu-Xiang
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p. 1995 - 1997
(2014/06/09)
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- Influence of silver on the glycerol electro-oxidation over AuAg/C catalysts in alkaline medium: A cyclic voltammetry and in situ FTIR spectroscopy study
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In the present work, we investigated the influence of silver on the glycerol electro-oxidation over carbon-supported AuAg catalysts by cyclic voltammetry and in situ FTIR spectroscopy. We observed that the presence of Ag in the bimetallic materials provided a more efficient catalyst in terms of the ability to electro-oxidize glycerol at relatively low potentials. On the other hand, the bimetallic catalysts were found to be less promising than the Au/C catalyst with respect to the reaction rate. Ag addition influenced the mechanism of glycerol electro-oxidation, favoring the C-C-C bond breaking, as evidenced by the selective formation of formic acid on the bimetallic catalysts. The impact of Ag on the glycerol electro-oxidation over AuAg/C may be driven by electronic modifications and Ag segregation on the catalysts surface.
- Gomes,Garcia,Gasparotto,De Souza,Ferreira,Pires,Tremiliosi-Filho
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p. 361 - 368
(2014/12/10)
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- SiO2-, Cu-, and Ni-supported Au nanoparticles for selective glycerol oxidation in the liquid phase
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We tested for the first time the efficiency of SiO2-, Cu-, and Ni-supported Au in deep glycerol oxidation in a diluted and viscous H2O2/H2O liquid phase. Acetic acid (AA), the C2 oxidate, was preferentially formed in such a system. High conversion (100%) and AA yields (90%) were observed for the sol-gel SiO2-supported Au in diluted solutions. Although with the increase of glycerol concentration in the viscous liquid phase these values decreased to ca. 40% (conversion) and 20% (AA yield), the addition of acetonitrile improved the AA yield to ca. 40%, while the surfactants were found to be capable of a many-fold enhancement of the catalyst activity at the room temperature highly viscous liquid phase. High performances were also observed for the bimetallic Au/Cu and Au/Ni catalysts obtained by nano-Au transfer; however, these catalysts were destroyed during the reaction by the Cu or Ni leaching effect.
- Kapkowski, Maciej,Bartczak, Piotr,Korzec, Mateusz,Sitko, Rafal,Szade, Jacek,Balin, Katarzyna,Lel?tko, Józef,Polanski, Jaroslaw
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p. 110 - 118
(2015/09/28)
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- Selective oxidation of alcohols over Ag-containing Si3N 4 catalysts
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Ag-containing ceramic catalysts modified or unmodified with Zr and Al were studied in selective catalytic oxidation of ethylene glycol and ethanol into the corresponding carbonyl compounds. The influence of phase and chemical composition of ceramic supports prepared by the self-propagating high-temperature synthesis (SHS) on the basis of silicon nitride was considered. The catalysts were characterized by X-ray diffraction, using scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDX) unit, and tested in selective oxidation of ethanol and ethylene glycol into acetaldehyde and glyoxal, respectively. It was shown that the presence of ZrO2 and Si3Al12O9N10 phases in the support composition allowed increasing glyoxal selectivity up to 50% at 87% conversion of glycol. Ag-containing ceramic catalysts also demonstrated high selectivity/activity in ethanol oxidation (95% acetaldehyde selectivity and 100% ethanol conversion at 300 °C), while the support phase composition did not influence the catalytic performance.
- Vodyankina, Olga V.,Blokhina,Kurzina,Sobolev,Koltunov, K.Yu.,Chukhlomina,Dvilis
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p. 127 - 132
(2013/08/24)
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- Meteorites as catalysts for prebiotic chemistry
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From outer space: Twelve meteorite specimens, representative of their major classes, catalyse the synthesis of nucleobases, carboxylic acids, aminoacids and low-molecular-weight compounds from formamide (see figure). Different chemical pathways are identified, the yields are high for a prebiotic process and the products come in rich and composite panels.
- Saladino, Raffaele,Botta, Giorgia,Delfino, Michela,Di Mauro, Ernesto
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p. 16916 - 16922
(2014/01/06)
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- Thermal and spectroscopic studies of Ni(II)-Fe(III) heteropolynuclear coordination compound obtained through the reaction of 1,2-ethanediol with metallic nitrates
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The oxidation reaction of 1,2-ethanediol (ethylene glycol, EG) with Ni(II) and Fe(III) metallic nitrates in aqueous solution was investigated. Also, the paper presents the experimental results of the thermal and spectroscopic studies of the synthesized Ni(II)-Fe(III)-heteropolynuclear coordination compound having as ligand oxidation product of ethylene glycol. Under specific working conditions, the reaction occurs with the oxidation of EG to glyoxylic acid, coordinated to the Ni(II) and Fe(III) cations as glyoxylate anion (C 2H2O42-, GA), with simultaneous isolation of heteropolynuclear coordination compound. In order to separate and identify the ligand, the synthesized coordination compound, having the composition formula is the main component of the conversion of the complex compound, [NiFe2(C2H2O4)2(OH) 4(H2O)4·1.5H2O]n, has been treated with R-H cationite (Purolite C-100). After the retention of the metal cations, the glyoxylic acid was characterized by measuring the physical constants, by specific reactions and spectroscopic methods. The structural investigations and thermal analysis of nickel ferriglyoxylate coordination compound, precursor of nickel ferrite are presented. The thermal properties of the synthesized polynuclear coordination compound have been investigated by TG, DTG and DSC. The mixed oxide obtained through thermolysis was characterized by IR, X-ray spectroscopy and elemental analysis.
- Niculescu, Mircea,Rosu, Dan,Ledeti, Ionut,Milea, Marius,Budrugeac, Petru
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p. 543 - 552
(2014/04/03)
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- Photocatalytic reversible amination of α-keto acids on a ZnS surface: Implications for the prebiotic metabolism
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We report the enzyme-like reversible amination of four intermediates pertinent to the reductive tricarboxylic acid cycle on a photo-irradiated surface of mineral sphalerite (ZnS). Given its prevalence in the waters of early Earth, we suggest that the mineral-based photochemistry might have catalyzed the homeostasis of prebiotic metabolic systems.
- Wang, Wei,Li, Qiliang,Yang, Bin,Liu, Xiaoyang,Yang, Yanqiang,Su, Wenhui
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supporting information; experimental part
p. 2146 - 2148
(2012/03/26)
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- Method For Improved Bioactivation Of Pharmaceuticals
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This invention relates to a prodrug comprising a partial structure having the general formula (I) or (II), where R1 and R2 are hydrogen, alkyl, or aryl radicals.
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Page/Page column 7; 9
(2012/04/05)
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- Efficient synthesis of DOPA analogues in pepticinnamins E via asymmetric catalytic hydrogenation of dehydroamino esters
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One practical synthetic procedure with five steps was developed to prepare a series of N-protected-2-(diethoxyphosphoryl)glycinates with good yields, which was treated with aldehydes under mild condition to give different dehydroamino esters with high yields and excellent Z/E selectivity. The subsequently homogeneous enantioselective hydrogenation of the dehydroamino esters affords a series of new DOPA analogues.
- Sun, De-Qun,Sun, Li,Luo, Min
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scheme or table
p. 1731 - 1734
(2012/08/28)
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- Mg-Al mixed oxides supported bimetallic au-pd nanoparticles with superior catalytic properties in aerobic oxidation of benzyl alcohol and glycerol
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Nano-sized Au and Pd catalysts are favorable for oxidations with molecular oxygen, and the preparation of this kind of nanoparticles with high catalytic activities is strongly desirable. We report a successful synthesis of bimetallic Au-Pd nanoparticles w
- Wang, Liang,Zhang, Wei,Zeng, Shangjing,Su, Dangsheng,Meng, Xiangju,Xiao, Fengshou
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p. 2189 - 2197
(2013/01/15)
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- OXIDATIVE CLEAVAGE OF UNSATURATED CARBOXYLIC ACIDS
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Provided are processes for the oxidative cleavage of a double bond in an unsaturated carboxylic acid. The process includes contacting the unsaturated carboxylic acid with a mild oxidizing agent and agitating the unsaturated carboxylic acid and the mild oxidizing agent for a time sufficient to cleave a double bond of the unsaturated carboxylic acid and produce a product comprising an aldehyde. The process is typically carried out in a mill, such as a ball, hammer, attrition, or jet mill.
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Page/Page column 15
(2011/05/05)
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- PROCESS FOR REMOVING HYDROGEN CYANIDE FROM ETHANEDINITRILE
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Process for removing hydrogen cyanide from ethanedinitrile by contacting hydrogen cyanide-containing ethanedinitrile with an organic reagent under formation of a covalent bond.
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- Au-Pd/C catalysts for glyoxal and glucose selective oxidations
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A series of Au-Pd/C catalysts were prepared on an activated carbon named SX PLUS (SX+) by fixing the pH of impregnation in aqueous phase at an optimal value for maximizing the interactions between metals and surface. This bimetallic association leads to highly active catalysts in the oxidation of glyoxal into glyoxalic acid and of glucose into gluconic acid, with the activity correlated to high surface Pd/C ratios measured by XPS and the presence of small metallic Pd particles, even if gold was present as big crystallites. A cooperative effect between the two metals was evidenced on the yield in carboxylic acids in both reactions, which is believed to arise from an interface between the two metals even if they are mostly present as separated phases. The incorporation of Au on Pd rather than the opposite and the concomitant activation of both metals influence positively the catalytic performance. The use of NaBH4 as activating agent allowed the most active Au-Pd/C catalyst to be obtained, with similar performances to the best bimetallic Bi-Pd/C catalyst so far but without any metal leaching.
- Hermans, Sophie,Deffernez, Aurore,Devillers, Michel
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experimental part
p. 19 - 27
(2012/01/03)
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- Monitoring of β-blockers ozone degradation via electrospray ionization mass spectrometry
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The structures of intermediate products of ozone degradation of different pharmaceutical compounds have been studied. Under the conditions employed, complete ozone degradation of nadolol was achieved after 100 min. The degradation products obtained in aqueous solution were characterized by electrospray ionization mass (and tandem mass) spectrometry (ESI-MS and ESI-MS/MS). The proposed mechanism for degradation, ozone attacks at the aniline amino group giving rise to nitro compounds and further degradation occurs via a series of oxidative processes. Continuous online monitoring by ESI-MS(/MS) with high accuracy mass measurements showed that ozone degradation of atenolol (ATE) and acebutolol (ACE) occurs via mechanisms similar to that of nadolol.
- Quispe, Cristina,Nachtigall, Fabiane M.,Fonseca, Maria Francesca R.,Alberici, Rosana M.,Astudillo, Luis,Villasen?or, Jorge,Eberlin, Marcos N.,Santos, Leonardo S.
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experimental part
p. 919 - 928
(2012/02/02)
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- Influence of Brij-35 micelles on the oxidation of glycine by hexacyanoferrate(III) in aqueous alkaline medium
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The kinetics of oxidation of glycine by hexacyanoferrate(III) in presence of non-ionic surfactant Brij-35 has been studied under pseudo-first order conditions in alkaline medium. It has been found that increase in [Brij-35] causes increase in reaction rate indicating that the reaction is enhanced by non-ionic micelles. The reaction is first order in [hexacyanoferrate(III)], [glycine] and (NaOH]. Glyoxalic acid is identified as the main product of oxidation.
- Goel, Anjali,Tyagi, Richa
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experimental part
p. 1335 - 1339
(2011/09/20)
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- Oxidation of some α-hydroxy acids by tetraethylammonium chlorochromate: A kinetic and mechanistic study
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The oxidation of glycolic, lactic, malic, and a few substituted mandelic acids by tetraethylammonium chlorochromate (TEACC) in dimethylsulfoxide leads to the formation of corresponding oxoacids. The reaction is first order each in TEACC and hydroxy acids. Reaction is failed to induce the polymerization of acrylonitrile. The oxidation of α-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (kH/kD = 5.63 at 298 K). The reaction does not exhibit the solvent isotope effect. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the following form: kobs = a + b[H+ ]. Oxidation of p-methylmandelic acid has been studied in 19 different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.
- Swami, Preeti,Yajurvedi,Mishra,Sharma, Pradeep K.
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experimental part
p. 50 - 55
(2010/04/06)
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- Kinetics and mechanisms for the reactions of ozone with unsaturated oxygenated compounds
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Rate coefficients for the reaction of ozone with a series of unsaturated oxygenated compounds are determined in air at atmospheric pressure and (298±3) K. Rate data are obtained using both relative and absolute rate techniques, and the measured rate coefficients are found to be in good agreement. The results show that the reactivity of the compounds with respect to addition of ozone to the double bond is a function of the nature of the oxygenated substituent. Product distribution studies on the reactions provide information on the decomposition pathways for the primary ozonides, and on the effect of the oxygenated group on the relative importance of the degradation pathways. The results are discussed in terms of their importance in the atmospheric oxidation of unsaturated oxygenated compounds.
- Al Mulla, Ismael,Viera, Lisa,Morris, Rebecca,Sidebottom, Howard,Treacy, Jack,Mellouki, Abdelwahid
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experimental part
p. 4069 - 4078
(2011/09/30)
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- The ozonization of model lignin compounds in aqueous solutions catalyzed by Mn(II) ions
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The influence of Mn(II) ions on the rate of the reaction between ozone and model lignin compounds, guaiacol and veratrole, was studied. The catalyst did not influence the rate of the destruction of the aromatic ring and intermediate ozonolysis products, compounds with conjugated double bonds, in acid media but substantially increased the rate of oxidation of saturated carboxylic acids, ketoacids, and aldehydes. Ozone consumption then increased from 2 to 5 moles per mole of the transformed substrate. A mechanism of the catalytic action of Mn(II) in reactions between ozone and the compounds studied was suggested.
- Mitrofanova,Khudoshin,Lunin
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body text
p. 1141 - 1146
(2011/01/09)
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- Degradation of an ether-alcohol (3-ethoxypropan-1-ol) by photo-Fenton-generated OH radicals: Products analysis and formation pathways; relevance to atmospheric water-phase chemistry
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We have chosen 3-ethoxypropan-1-ol (EtOPrOH) as a typical shortcarbon- chain ether-alcohol used as industrial solvent and have analyzed the degradation products resulting from its attack by OH radicals generated by the photo-Fenton reaction. The laboratory conditions were representative of those found in tropospheric water droplets. Twelve products have been identified by use of GC- MS analysis, either directly or after extraction by SPME fibers, and by HPLC-UV analysis with a special column for carboxylic acids and after reaction of carbonyl groups with 2,4-dinitrophenylhydrazine. These products contain one to three carbon atoms (instead of five in EtOPrOH), among which one or two are oxidized. According to the reaction pathways proposed, seven products-including methanal- can result from attack by one OH only, three products imply attack by a second OH, as expected from their higher oxidation number, and it is suggested that reaction between two organic radicals is needed for formation of only two products. The relevance of this investigation to the fate of EtOPrOH and similar ether-alcohols in the troposphere is briefly discussed. Springer Science+Business Media B.V. 2010.
- Carteau, David,Pichat, Pierre
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experimental part
p. 141 - 153
(2011/10/19)
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- PROCESS OF PREPARATION OF GLYOXYLIC ACID AQUEOUS SOLUTION
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The invention relates to a method for preparing an aqueous solution of glyoxylic acid by oxidation of an aqueous solution of glyoxal with oxygen or a gas containing oxygen, in the presence of a catalytic quantity of nitric acid and/or at least one nitrogen oxide, a strong acid not oxidizing glyoxal, and by maintaining conditions satisfying the equation KLa/Q > 10, where KLa is the total volumetric mass transfer coefficient and Q is the heat load liberated by the reaction per mole of glyoxal.
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Page/Page column 7-8
(2009/09/05)
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- Imino-oxy acetic acid dealkylation as evidence for an inner-sphere alcohol intermediate in the reaction catalyzed by peptidylglycine α-hydroxylating monooxygenase
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Peptidylglycine α-hydroxylating monooxygenase (PHM, EC 1.14.17.3) catalyzes the stereospecific hydroxylation of a glycyl α-carbon in a reaction that requires O2 and ascorbate. Subsequent dealkylation of the α-hydroxyglycine by another enzyme, peptidylamidoglycolate lyase (PAL. EC 4.3.2.5), yields a bioactive amide and glyoxylate. PHM is a noncoupled, type II dicopper monooxygenase which activates O2 at only a single copper atom, CuM. In this study, the PHM mechanism was probed using a non-natural substrate, benzaldehyde imino-oxy acetic acid (BIAA). PHM catalyzes the O-oxidative dealkylation of BIAA to benzaldoxime and glyoxylate with no involvement of PAL. The minimal kinetic mechanism for BIAA was shown to be steady-state ordered using primary deuterium kinetic isotope effects. The D(V/K)APPARENT, BIAA decreased from 14.7 ± 1.0 as [O2] → 0 to 1.0 ± 0.2 as [O2] → ∞ suggesting the dissociation rate constant from the PHM·BIAA complex decreases as [O2] increases; thereby, reducing the steady-state concentration of [PHM]free. BIAA was further used to differentiate between potential oxidative Cu/O species using a QM/MM reaction coordinate simulation to determine which species could yield product O-dealkylation that matched our experimental data. The results of this study provided compelling evidence for the presence of a covalently linked CuII-alkoxide intermediate with a quartet spin state responsible BIAA oxidation.
- McIntyre, Neil R.,Lowe Jr., Edward W.,Merkler, David J.
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experimental part
p. 10308 - 10319
(2009/12/08)
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- Chemical transformations of pyridoxal and pyridoxal 5′-phosphate condensation products with amino acids
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The mechanism of chemical transformations of pyridoxal and pyridoxal 5′-phosphate condensation products with amino acids is studied by kinetic measurements. The Schiff bases are shown to be fairly stable in neutral media. In acid media, the Schiff bases a
- Pishchugin,Tuleberdiev
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p. 1225 - 1229
(2008/12/22)
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- Photocatalytic oxidation of ethanol during hydrogen generation from water-ethanol mixture over gadolinium-doped titania
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Photocatalytic hydrogen generation from water in the presence of ethanol as a sacrificial reagent was studied over gadolinium doped TiO2 photocatalyst. Photocatalytic pathways of ethanol oxidation were studied with liquid 1H NMR spectroscopy. The 1H NMR results were compared with amounts of evolved hydrogen and carbon dioxide. Acetal-dehyde, acetic acid, glycolic acid and glyoxylic acid were found as major intermediates of this process, whereas carbon dioxide evolution was the last step during ethanol photooxidation process. The mechanism of ethanol photooxidation has been proposed.
- Zalas,Gierczyk,LAniecki
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experimental part
p. 1767 - 1777
(2009/04/05)
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- Kinetics and mechanism of the oxidation of some α-hydroxy carboxylic acids by [bis(trifluoroacetoxy)iodo]benzene
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The oxidation of α-hydroxy carboxylic acids by [bis(trifluoroacetoxy) iodo]benzene (TFAIB), to the corresponding oxoacids is first order with respect to each, the hydroxy acid, TFAIB and hydrogen ions. The oxidation of α-deuteriomandelic acid (PhCDOHCO2H) exhibits the presence of a substantial primary isotope effect confirming the cleavage of the α - C - H bond in the rate-determining step. The rate of oxidation of substituted mandelic acids correlates well with Brown's σ+ values with large negative reaction constants. A mechanism involving transfer of a hydride ion from the hydroxy acid to the oxidant has been postulated.
- Banerji, Jayshree,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 445 - 448
(2008/02/09)
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- Mechanistic study of Pd(II) catalysed oxidation of maleic and crotonic acids by N-chlorosuccinimide in perchloric acid medium
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The kinetics of oxidation of maleic and crotonic acids by N-chlorosuccinimide (NCS) in perchloric acid are presented. Analysis of the results shows that the observed rates of oxidation indicate zero order in [substrate] and [H+]. First order dependence of the reactions on NCS at its lower concentrations tends to zero order in its higher concentration range. The reaction rate increases with increase in [Pd(II)] but the order in [Pd(II)] is less than unity. The initial addition of CP and five fold excess of added succinimide (NHS) do not affect the rate significantly. Increase in ionic strength has negligible effect on the rate while increase in acetic acid content in reaction medium decreases the rate. Mechanistic steps are discussed on the basis of kinetic observations and products analysis.
- Ashish,Singh, Chhaya,Singh, Ashok Kumar,Singh, Bharat
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p. 476 - 482
(2007/10/03)
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- IN-SITU DECOMPOSITION OF PEROXIDES DURING THE OZONOLYSIS OF ALKENES
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The invention relates to a method for carrying out the in-situ decomposition of peroxides during the ozonolysis of optionally substituted alkenes in order to form the corresponding aldehydes or ketones. According to the method, the optionally substituted alkenes are reacted in water, a C1-C4 carboxylic ester, a C1-C4 carboxylic acid, a water/C1-C4 carboxylic acid mixture, a C1-C6 alcohol or in a water/C1-C6 alcohol mixture at a temperature ranging from -30 °C to +50 °C, in the presence of a heterogeneous inorganic catalyst selected from the group consisting of iridium, manganese, cobalt, silver, gold, palladium, platinum or ruthenium, which is applied to a supporting material selected from the group consisting of calcium carbonate, coal, titanium dioxide, magnesium oxide, zirconium oxide, silica or aluminum oxide or in the presence of a homogeneous inorganic catalyst selected from the group consisting of transition metal catalysts while simultaneously decomposing peroxides with ozone. Afterwards, the catalyst is separated out from the reaction mixture once the ozonolysis is complete thus obtaining corresponding aldehydes and ketones.
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- Kinetics of oxidation of crotonic acid by sodium N-chloro-p- toluenesulphonamide in the presence of Pd(II) and Os(VIII) as homogeneous catalysts
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The kinetics of Pd(II) and Os(VIII) catalysed oxidation of crotonic acid (CA) by chloramine-T (CAT) in perchloric acid have been investigated. The reactions are zero order in [chloramine-T] and first order each in both [Pd(II)] and [Os(VIII)], while first order in [CA] at lower concentrations tending towards zero order at its higher concentrations. Positive effect of added [Cl-] and zero effect of added p-toluenesulphonamide (PTS) have been observed in Pd(II) catalysed reaction, while in Os(VIII) catalysed reaction negative effect of PTS on rate of reaction has been observed. Negligible effect of change in [H+] and ionic strength of the medium, and rate decrease with decrease in dielectric constant of the medium have been observed in both Pd(II) and Os(VIII) catalysed reactions. The catalytic efficiency is in the order, Pd(II) > Os(VIII). The products of oxidation in both reactions are acetaldehyde and glyoxylic acid. Activation parameters have been computed and mechanistic steps, consistent with the kinetic results, reaction stoichiometry and product analysis for both catalysed reactions have been discussed.
- Ashish,Singh, Ajaya Kumar,Singh, Ashok Kumar,Singh, Bharat
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p. 1645 - 1653
(2007/10/03)
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