- Ethylene glycol, 2-propanol electrooxidation in alkaline medium on the ordered intermetallic PtPb surface
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The ethylene glycol and 2-propanol electrooxidation reaction was studied on carbon dispersed ordered intermetallic PtPb nanocatalysts in KOH solution. X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize ordered intermetallic PtPb/C catalysts. The electrochemical behaviors for the ethylene glycol and 2-propanol electrooxidation reaction were measured in a thin film electrode by cyclic voltammetry, Tafel curves and electrochemical impedance spectroscopy. The results showed that in contrast with PtRu/C and Pt/C catalyst, ordered intermetallic PtPb/C had better electroactivity, and kinetic mechanism of PtPb/C is complex. Although the activity of electrocatalysts depends on many factors, such as modification of geometric and electronic structure by Pt-Pb interaction, crystalline size and so on. But the key factor for each electrooxidation reaction was different. For ethylene glycol electrooxidation, the effect of formation and desorption of poisonous species on activity of catalyst was very significant. For 2-propanol electrooxidation, the modification of geometric and electronic structures may be play a decisive role in the enhance activity of electrocatalyst.
- Feng, Yanyan,Yin, Wenping,Li, Zhi,Huang, Chengde,Wang, Yuxin
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- Synthesis, characterization and the thermal decomposition of potassium tris(oxalato)lanthanum(III)nonahydrate
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Potassium tris(oxalato)lanthanum(III)nonahydrate, K3[La(III)(C2O4)3]·9H 2O, has been synthesized and characterized by elemental analysis and IR spectral studies. Thermal studies (TG, DTG and DTA) in air showed that the anhydrous compound formed at ca. 192°C. The final end product at 1000°C was shown to be a mixture of La2O3, K2CO3, K2O, KLaO2 and La2C3, through the formation of an intermediate mixture of K2C2O4 and K[La(C2O4)x] (where 1.5 2C2O4 and La2O2CO3 at ca. 528°C. DSC study in nitrogen upto 650°C showed that the end product was a mixture of K2C2O4 and La2O2CO3. The kinetic parameters, mainly E* of the dehydration and decomposition steps in TG, were calculated using four non-mechanistic equations. The kinetic parameters, E*, ΔH, ΔS obtained from DSC study are discussed. Some of the decomposition products were identified by IR and X-ray powder diffraction studies. A tentative mechanism for the decomposition in air is proposed.
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- Countercations and Solvent Influence CO2 Reduction to Oxalate by Chalcogen-Bridged Tricopper Cyclophanates
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One-electron reduction of Cu3EL (L3- = tris(β-diketiminate)cyclophane, and E = S, Se) affords [Cu3EL]-, which reacts with CO2 to yield exclusively C2O42- (95% yield, TON = 24) and regenerate Cu3EL. Stopped-flow UV/visible data support an A→B mechanism under pseudo-first-order conditions (kobs, 298K = 115(2) s-1), which is 106 larger than those for reported copper complexes. The kobs values are dependent on the countercation and solvent (e.g., kobs is greater for [K(18-crown-6)]+ vs (Ph3P)2N+, and there is a 20-fold decrease in kobs in THF vs DMF). Our results suggest a mechanism in which cations and solvent influence the stability of the transition state.
- Cook, Brian J.,Di Francesco, Gianna N.,Abboud, Khalil A.,Murray, Leslie J.
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- Recognition of dicarboxylate anions by a ditopic hexaazamacrocycle containing bis-p-xylyl spacers
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The hexaprotonated form of the hexaazamacrocycle, 7,22-dimethyl-3,7,11,18, 22,26-hexaazatricyclo[26.2.2.2.13.16]tetratriaconta-1(30),13,15,28,31, 33-hexaene, (H6Me2[30]pbz2N6) 6+, was used as a receptor for the molecular recognition of aliphatic and aromatic carboxylate substrates. The receptor-substrate binding behaviour of (H6Me2[30]pbz2N6)6+ with aliphatic > -O2C(CH2) nCO2-, n = 0 to 4] and aromatic (benzoate, phthalate, isophthalate, and terephthalate) substrates was evaluated by potentiometry and 1H NMR spectroscopy. The association constants of the entities formed were determined in H2O at 298.0 K and 0.1 M KNO3 (by potentiometry) and in D2O (by 1H NMR). The constants for the aliphatic substrates are much lower than for the aromatic ones. NMR spectroscopy allowed the conclusion that the recognition process might involve H-bonding, electrostatic and π-π stacking interactions, the strength and the type of them depending on the substrate. The cooperative conjugation of the three types of interactions only occurs when terephthalate is the substrate. Molecular dynamics simulations (MD) in a periodic box of water solvent molecules were also used to investigate the nature of the binding association between the receptor and the three aromatic dicarboxylate anions (phthalate, isophthalate, and terephthalate). These studies confirmed that the (H6Me2[30]pbz2N6)6+ receptor encapsulates the terephthalate anion with the formation of an inclusion supermolecule stabilized by multiple N-H...O hydrogen bonding and π-π interactions. The molecular recognition between the receptor and the other two aromatic anions, phthalate and isophthalate, also occurs via N-H...O hydrogen bonds, but outside of the macrocyclic cavity. The results are discussed in terms of energetic and entropie contributions and showed that the binding association between the receptor and these anions is favourable. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
- Carvalho, Silvia,Delgado, Rita,Fonseca, Nelson,Felix, Vitor
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- Electrooxidation of ethylene glycol and glycerol on Pd-(Ni-Zn)/C anodes in direct alcohol fuel cells
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The electrooxidation of ethylene glycol (EG) and glycerol (G) has been studied: in alkaline media, in passive as well as active direct ethylene glycol fuel cells (DEGFCs), and in direct glycerol fuel cells (DGFCs) containing Pd-(Ni-Zn)/C as an anode electrocatalyst, that is, Pd nanoparticles supported on a Ni-Zn phase. For comparison, an anode electrocatalyst containing Pd nanoparticles (Pd/C) has been also investigated. The oxidation of EG and G has primarily been investigated in half cells. The results obtained have highlighted the excellent electrocatalytic activity of Pd-(Ni-Zn)/C in terms of peak current density, which is as high as 3300A g(Pd)-1 for EG and 2150A g(Pd)-1 for G. Membrane-electrode assemblies (MEA) have been fabricated using Pd-(Ni-Zn)/C anodes, proprietary Fe-Co/C cathodes, and Tokuyama A-201 anion-exchange membranes. The MEA performance has been evaluated in either passive or active cells fed with aqueous solutions of 5wt % EG and 5wt % G. In view of the peak-power densities obtained in the temperature range from 20 to 80 °C, at Pd loadings as low as 1mg cm -2 at the anode, these results show that Pd-(Ni-Zn)/C can be classified amongst the best performing electrocatalysts ever reported for EG and G oxidation. Copyright
- Marchionni, Andrea,Bevilacqua, Manuela,Bianchini, Claudio,Chen, Yan-Xin,Filippi, Jonathan,Fornasiero, Paolo,Lavacchi, Alessandro,Miller, Hamish,Wang, Lianqin,Vizza, Francesco
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p. 518 - 528
(2013/06/05)
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- E versus Z diazeniumdiolation of acetoacetate-derived carbanions
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Nitric oxide adds to methyl acetoacetate in the presence of KOH in methanol at room temperature to form potassium acetylsydnonate N-oxide (K1) with an (E)-diazeniumdiolation and potassium acetate diazenium diolate (K22) from a (Z)-diazeniumdiolation. A study of the reaction with LiOH, NaOH, and NMe4OH and with ethyl acetate substrate reveals that the temperature of the reaction greatly influences the nitric oxide reactivity. At 23 °C, nitric oxide adds to give both E and Z products, whereas at -5 °C the gas reacts almost exclusively to give Z addition. The (Z)-diazeniumdiolation products, namely, the alkali metal and NMe4+ salts of methyl and ethylbutenoate-2-diazeniumdiolate-3-hydroxylate (32- and 42-), are isolated in good yields. The alkali metal salts are not amenable for recrystallization because of their ready decomposition in aqueous solutions. However, [NMe4]2[MeC(O)C(N2O 2)CO2Me] is readily recrystallized from a methanol/acetonitrile solvent mixture. The crystals are unambiguously characterized by X-ray crystallography. NMR spectra for all of the 3 2- and 42- salts reveal the presence of two isomers in aq solutions. But the structure of the NMe4+ salt contains only one of the isomers. Our attempts to cyclize the isolated and purified butenoatediazeniumdiolates from the (Z)-diazeniumdiolation to the E-containing sydnonate products were unsuccessful. TGA/DSC data for all of the products demonstrate the thermal instability of the salts at high temperatures. The salts decompose exothermally possibly with the release of N2O among other gases.
- Arulsamy, Navamoney,Holman, Carla L.,Bohle, D. Scott,Perepichka, Inna
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p. 7313 - 7318,6
(2020/08/24)
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- Cis-diiodo-(trans-l-1,2-cyclohexanediamine) platinum (II) complex and processes for preparing high purity oxaliplatin
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The present invention is related to pure cis-diiodo-(trans-L-1,2-cyclohexanediamine) Pt (II) complex, and a process of its preparation. The present invention is further related to the preparation of oxaliplatin using said cis-diiodo-(trans-L-1,2-cyclohexanediamine) Pt (II) complex.
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Page/Page column 8
(2010/10/19)
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- Crystal and molecular structures of alkali oxalates: First proof of a staggered oxalate anion in the solid state
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The molecular and crystal structures of solvent-free potassium, rubidium, and cesium oxalates have been determined ab initio from high-resolution synchrotron and X-ray laboratory powder patterns. In the case of potassium oxalate K2C2O4 (a = 10.91176(7) A, b = 6.11592(4) A, c = 3.44003(2) A, orthorhombic, Pbam, Z = 2), the oxalate anion is planar, whereas in cesium oxalate Cs2C2O4 (a = 6.62146(5) A, b = 11.00379(9) A, c = 8.61253(7) A, β = 97.1388(4)°, monoclinic, P21/c, Z = 4) it exhibits a staggered conformation. For rubidium oxalate at room temperature, two polymorphs exist, one (β-Rb2C2O4) isotypic to potassium oxalate (a = 11.28797(7) A, b = 6.29475(4) A, c = 3.62210(2) A, orthorhombic, Pbam, Z = 2) and the other (α-Rb2C2O4) isotypic to cesium oxalate (a = 6.3276(1) A, b = 10.4548(2) A, c = 8.2174(2) A, β = 98.016(1)°, monoclinic, P21/c, Z = 4). The potassium oxalate structure can be deduced from the AIB2 type, and the cesium oxalate structure from the Hg99As type, respectively. The relation between the two types of crystal structures and the reason for the different conformations of the oxalate anion are discussed.
- Dinnebier, Robert E.,Vensky, Sascha,Panthoefer, Martin,Jansen, Martin
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p. 1499 - 1507
(2008/10/08)
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- Novel Synthesis of Oxalate from Carbon Dioxide and Carbon Monoxide in the Presence of Caesium Carbonate
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In the presence of caesium carbonate 1, the direct reaction of CO2 (110 atm) with CO (20 atm) results in reductive capture of CO2 to give caesium oxalate 2 in good yield at elevated temperature (380 deg C).
- Kudo, Kiyoshi,Ikoma, Futoshi,Mori, Sadayuki,Komatsu, Koichi,Sugita, Nobuyuki
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p. 633 - 634
(2007/10/02)
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- Applications of real-time FTIR spectroscopy to the elucidation of complex electroorganic pathways: electrooxidation of ethylene glycol on gold, platinum, and nickel in alkaline solution
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The electrooxidation pathways of ethylene glycol in alkaline aqueous solution on gold, platinum, and nickel electrodes are explored by means of real-time FTIR spectroscopy in conjunction with cyclic voltammetry. The former enables a quantitative assay of specific intermediates and products formed during the reaction evolution. The electrooxidation on gold features the successive formation of partially oxidized C2 solution species en route to oxalate and carbonate production. The latter species is produced predominantly via the formation of the dialdehyde, glyoxal, based on comparisons with electrooxidative spectral sequences for candidate intermediate species. In contrast, ethylene glycol electrooxidation on platinum exhibits markedly different kinetics and product distributions to those for the partially oxidized C2 species, inferring that at least carbonate production from ethylene glycol occurs largely through sequences of chemisorbed, rather than solution-phase, intermediates. Electrooxidation of ethylene glycol and higher polyols on nickel display a remarkably selective production of formate. This efficient oxidative C-C bond cleavage on nickel is displayed in somewhat different fashion for partially oxidized C2 reactants in that carbonate is predominantly formed. Some possible surface chemical factors responsible for these striking mechanistic differences are discussed.
- Chang, Si-Chung,Ho, Yeunghaw,Weaver, Michael J.
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p. 9506 - 9513
(2007/10/02)
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- Carbanions. Electron Transfer vs. Proton Capture. 7. Electron-Transfer Oxidation of an Amino Acid Derived Carbanion
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The dimethylamide of phenylalanine, 1, reacts with potassium tert-butoxide and nitrobenzene in tert-butyl alcohol at 50 deg C in argon atmosphere.The products are potassium nitrobenzenide (PhNO2-*K+)and degradative fragments of the amino amide, including ammonia, dimethylamine, potassium benzoate, potassium carbonate, and potassium cyanide.The yields of these isolated degradation products are relatively low when the reaction is run anaerobically but are improved when the reaction is carried out under oxygen.The oxygen-mediated reaction does not produce cyanide or nitrobenzenide but its products are otherwise the same with the addition of oxalate.Conversions are essentially quantitative when the oxygen-mediated reaction is followed by vigorous, acid-catalyzed, hydrolytic workup.The reaction is believed to begin with the one-electron oxidation of the α-amino carbanion, proceeding through a ketimine and/or enamine which is rapidly oxidized to the eventual products.The rate of oxidation of 1 is approximately the same as its ionization rate but the reaction becomes less efficient if the N-pivalyl derivative of 1 is used.Experiments with the dimethylamide of alanine give qualitatively similar results, with potassium formate replacing potassium benzoate in the products.
- Guthrie, Robert D.,Hrovat, David A.,Prahl, Fredrick G.,Swan, James
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p. 498 - 501
(2007/10/02)
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