Kinetics of the Reaction of Abstracting Hydrogen from Ethylene by Hydrogen Atom

Hydrogen abstraction reaction, H C2H4 --H2 C2H2 was studied by using A initio SCF method. Ge-ometries were fully optimized at SCF level and energies were computed at STO-3G basis set for reactants and transition state. Vibrational analysis was performed thereupon. Finally, the rate constant calculations were carried out at different temperatures for all range of reaction temperature according to Eyring's sbwlute reaction rate theory. The calculated activation energy is 12. 68 kcal/mol, lower than observed value (H. S kcal/mol) by 1. 82 kcal/mol only. The agreement of the calculated rate constants with the experiments is satisfactory.     

Hydrogen–oxygen fuel cells

Ion exchange non-fluorinated membranes were tested in half-cells used as models for hydrogen–oxygen fuel cells. The lower acidity of the membranes allowed us to reduce the chemical stability requirements for the construction and catalytic materials. The maximum energy yield at room temperature was close to 65% at a current density of 40–60 mA cm^–2.Presented at the 3rd International Meeting on Advanced Batteries and Accumulators, 16–20 June 2002, Brno, Czech Republic     

Antitumour Acitivty of Chitosan Hydrogen Selenites

Chitosans reacted with selenious acid to prepare chitosan hydrogen selenites, which were found to be growth-inhibitory against sarcoma 180 solid tumor. The results indicated that the activity also depended on the molecular weight of chitosan supports.     

Yields of Hydrogen and Hydrogen Peroxide from Argon–Water Vapor in Dielectric Barrier Discharge

Controlled chemical transformation of water vapor in dielectric barrier discharge (DBD) of argon into hydrogen and hydrogen peroxide for its usability as in situ or ex situ H₂ and H₂O₂ source are reported. Online analysis of the product gas mixture by conventional wet-chemical colorimetric method using buffered KI absorber solution revealed typical H₂O₂ G-value = 6.4 × 10^?3 µmol J^?1 (G-value defines as the number of molecules produced/consumed per 100 eV of energy; in SI unit G-value is expressed in µmol J^?1) in the absence of ozone. On the other hand, H₂ in product mixture analyzed in gas chromatograph-thermal conductivity detector (GC-TCD) with argon carrier revealed its G-value = 0.134 µmol J^?1. Enhancements in products’ yields were explored by varying gas residence time inside the plasma zone, and applied voltage and frequency on the dielectric surfaces. Employing a double-DBD reactor, at applied high voltage ~2.5 kV mm^?1 @50 Hz and gas residence time ~20 s resulted in the highest yields of H₂O₂. However, the H₂ yield increased continuously with increase in gas residence time. On the other hand, the single-dielectric barrier surface reactors were more efficient for high and exclusive generation of ex situ H₂ (e.g. maximum 1260 ppm; G-value typically 0.498 µmol J^?1).     

Hydrogen Shows Promise in Vehicle Tests

Car fleets escorted by police along Chang‘an Avenue are not a rare sight for Beijing residents, who are accustomed to the practice when leaders of foreign states visit the capital of China.     

Antitumour Activity of Chitosan Hydrogen Selenites

Selenium is a biologically important element and essential for life1. Selenium deficiency causes severe degenerative disease, such as Kesan cardiomyopathy, and has been implicated in increasing the incidence of human cancer and some chronic ailment as well as ageing. Administration of selenium compounds such as sodium selenite protects animals against carcinogens and markedly reduces the incidence of various neoplasms in human2. Chitosan is one of the most abundant glycans in nature and its…     

Studies on Ion-Beam Modified Hydrogen Evolution Electrodes

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Hydrogen Production from Methanol Using Corona Discharges

Hydrogen production at room temperature from liquid methanol has been conducted using corona discharge.The content of water in methanol solution has a significant effect on this production.When water concentration increases from 1.0% to 16.7,the methanol conversion rate changes from 0.196 to 0.284 mol/h.An important finding in this investigation is the formation of ethylene glycol as a major by-product.The yield of ethylene glycol is ranged from 0.0045 to 0.0075 mol/h based on the water content.     

Intramolecular Hydrogen Bonding Restricts Gd–Aqua-Ligand Dynamics

Aqua ligands can undergo rapid internal rotation about the M−O bond. For magnetic resonance contrast agents, this rotation results in diminished relaxivity. Herein, we show that an intramolecular hydrogen bond to the aqua ligand can reduce this internal rotation and increase relaxivity. Molecular modeling was used to design a series of four Gd complexes capable of forming an intramolecular H-bond to the coordinated water ligand, and these complexes had anomalously high relaxivities compared to similar complexes lacking a H-bond acceptor. Molecular dynamics simulations supported the formation of a stable intramolecular H-bond, while alternative hypotheses that could explain the higher relaxivity were systematically ruled out. Intramolecular H-bonding represents a useful strategy to limit internal water rotational motion and increase relaxivity of Gd complexes.     

Hydrogen Bonds in Coal -The Influence of Coal Rank and the Recognition of a New Hydrogen Bond in Coal

By means of in-situ diffuse reflectance FTIR.The IR spectra of 6 coals with different ranks were obtained from room temperature to 230℃.A new curve fitting method was used to recognize the different hydrogen bonds in the coals.and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed.The results show that there is another new HB(around 2514cm^-1) between the-SH in mercaptans or thiophenols and the nitrogen in the pyridine-like compounds in the coals.and the evidence for that was provided.The controversial band of the HB between hydroxyl and the nitrogen of the pyridine-like compounds was determined in the range of 3028-2984cm^-1,and the result is comsistent with but more specific than that of Painter et al.It was ound that the stability of different HBs in the coals is influenced by both coal rank and temperature,For some HBs.the higher the coal rank,the higher the stability of them.Within the temperature range of our research,the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140℃.     

Macrocyclic β-Sheets Stabilized by Hydrogen Bond Surrogates

Mimics of protein secondary and tertiary structure offer rationally-designed inhibitors of biomolecular interactions. β-Sheet mimics have a storied history in bioorganic chemistry and are typically designed with synthetic or natural turn segments. We hypothesized that replacement of terminal inter-β-strand hydrogen bonds with hydrogen bond surrogates (HBS) may lead to conformationally-defined macrocyclic β-sheets without the requirement for natural or synthetic β-turns, thereby providing a minimal mimic of a protein β-sheet. To access turn-less antiparallel β-sheet mimics, we developed a facile solid phase synthesis protocol. We surveyed a dataset of protein β-sheets for naturally observed interstrand side chain interactions. This bioinformatics survey highlighted an over-abundance of aromatic–aromatic, cation-π and ionic interactions in β-sheets. In correspondence with natural β-sheets, we find that minimal HBS mimics show robust β-sheet formation when specific amino acid residue pairings are incorporated. In isolated β-sheets, aromatic interactions endow superior conformational stability over ionic or cation-π interactions. Circular dichroism and NMR spectroscopies, along with high-resolution X-ray crystallography, support our design principles.     

Preparation and Crystal Structure of Sodium Hydrogen Epoxysuccinate

1 INTRODUCTION In recent years, sodium hydrogen epoxysuccinatehas gained special attention as a raw material of po-lyepoxysuccinic acid (PESA)[1～3]. We have synthes-ized sodium hydrogen epoxysuccinate by the reac-tion of H2O2 and maleic anhydride in water ca-talyzed by tungstate and obtained its single crystal[1].Its structure was determined by X-ray Nonius CAD4diffractometer. Up to now some crystal structures oforganic carboxyl sodium have been determined[4～6].In this paper we …     

A New Catalyst for Hydrogen Transfer Hydrogenation of Acetophenone

OPticallyachvesecondaryalcoholsareimPOrtantintermediatesintheopthesisofaVdrietyofphysiologicall}activephannaceutitalsI']Althoughwell-knownchiralcatalyStssuchasL-DIOPRh(l)andBtwAPRu(II)caneffechvelycatalyZetheaSymmetrichydrOgentransferhydrOgenationOfketoneswithfunctionalgrouPs,thehydrOgentransferhydrQgnaionofsimplearomaticketonesisstillddriculttoberealizedI2].WehavesuccesffellyusedrUtheniumcomP1exeswithbiphosphineoraininophosphjneligandS,designedandSynthesizedbyourlaboratory,astheca…     

Conversion of Methane to Hydrogen via Pulsed Corona Discharge

Experiments are performed to develop a pulsed corona discharge system for the conversion ofmethane to hydrogen at atmospheric pressure (≌760 Torr) without using a catalyst. The corona dischargewas energized by 10-12 μs wide voltage pulses (≤7 kV) at a repetition rate of about 1.0-1.5 kHz. Theresidual gases were characterized by mass spectrometry. The conversion of methane is as high as 50.8% producing the 70% yield of hydrogen. The influences of argon on the discharge of methane were studied.This result could be useful for the mass production of hydrogen in both academic and industrial point ofview.     

Hydrogen Bonds at Silica – Polyvinylpyrrolidone – Water Interfaces

The effect of the adsorption of polyvinylpyrrolidone on the surface of highly dispersed silica on the state of interfacial water was studied by ¹H NMR spectroscopy and thermally stimulated depolarization with freezing out of the bulk water.     

A Novel Fluorescent Reagent for Analysis of Hydrogen Peroxide

IntroductionTheoxidationofmanyclinicalsubstancesinbodyfluidsproducesaquantityofhydrogenperoxide ,sothedetermina tionoftracehydrogenperoxideisofconsiderableimportanceinclinicalchemistry .1Further,themonitoringofhydrogenperoxideisalsonecessarytoenvironmentalsciencesinceitisakeyspeciesinthereactionsofthetroposphere,beingin volvedinimportantreactionssuchasthecatalyzedoruncat alyzedaqueousphaseoxidationofSO2 andtheultraviolet en hancedaqueousphaseoxidationoforganicspecies.2 Uptonow ,variousmethods…