bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Ethanol Impregnation on the Catalytic Properties of Silica‐Supported Cobalt Catalysts
Authors: Ho Sui‐Wen , Su Yu‐Shu 
Published: May 2015

AbstractSilca‐supported Co3O4 (6 wt% as Co) catalysts were prepared by pore volume impregnation of ethanol or aqueous cobalt nitrate solutions, and calcined in vacuo to 300 °C. The catalytic performances of these catalysts for oxidation and hydrogenation of CO were examined. All Co3O4/SiO2 catalysts were found to be very active in catalyzing oxidation of CO to CO2 as compared to a commercial 1 wt% Pt/Al2O3. The ethanol‐prepared catalysts exhibited higher activity than those of the aqua‐prepared catalysts. Pre‐calcination of the ethanol‐prepared catalysts in oxygen at 600 °C resulted in a dramatic decrease in the activity. Temperature programmed oxidation indicated the presence of carbon deposits on the surface of used catalysts. Infrared spectra showed the continuous generation of CO2 when these catalysts were exposed to CO. These indicate the primary role of CO disproportionation in catalytic oxidation of CO on Co3O4 at low temperature and explain the sharp decrease in activity in the initial period. After reduction at 400 °C, the ethanol‐prepared catalysts were also found to be more active in catalyzing hydrogenation of CO, and produced less methane and olefin (C2‐C4) fraction. Higher turnover frequencies were observed after high temperature reduction (600 °C) as well, at which ethoxyl groups were removed from silica surface. In both reactions, the enhanced activity for the ethanol‐prepared catalysts can not be fully accounted for by the increase in the dispersion of Co3O4 or CO metal. This suggests that the surface structures of Co3O4 or CO were further modified by the carbonaceous species derived from ethanol.
Heterocycles from Pyrazoloylhydroximoyl Chloride: Synthesis of Certain Quinoxaline, Benzothiadiazine, Benzoxadiazine, Quinazolinone, Imidazo[1,2‐a]pyridine, Imidazo[1,2‐a]pyrimidine, Isoxazole, Pyrazolo[3,4‐d]pyridazine and Pyrrolidino[3,4‐d]isoxazolin‐4,6‐dione Derivatives
Authors: Zohdi Hussein F. , Osman Tabia A. , Abdelhamid Abdou O. 
Published: May 2015

Abstract3‐Ethoxycarbonyl‐5‐methyl‐1‐(4‐methylphenyl)‐4‐pyrazoloylhydroximoyl chloride (1) reacted with o‐phenylenediamine, o‐aminothiophenol, o‐aminophenol and methyl anthranilate to afford 3‐nitrosoquinoxaline, benzothiadiazine, benzoxadiazine, and 3‐hydroxyquinazoline, respectively. Imidazo[1,2‐a]pyridine, imidazo[1,2‐a]pyrimidine and isoxazole derivatives were obtained via the reaction of 1 with 2‐aminopyridine, 2‐aminopyrimidine and the appropriate active methylene compounds, respectively. Pyrazolo[3,4‐d]pyridazines, and pyrrolidino[3,4‐d]isoxazolines derivatives were also synthesized. The structures of the newly synthesized compounds were established on the basis of spectral data and alternate synthesis whenever possible.
Lewis Acid‐Promoted Reduction of Bis(triorganotin) Oxides to Hexaorganoditins
Authors: Lee Adam Shih‐Yuan , Zhang Shi‐Lien , Pan Ohm‐Guo 
Published: May 2015

AbstractHexalkylditin is prepared by a Lewis acid‐promoted (MgCl2) reductive reaction of bis(trialkyltin) oxide using magnesium metal as reducing agent. Hexabutyl‐ and hexaphenylditin are synthesized with 95% and 80% yield separately and a radical mechanism is proposed for the reaction condition. Unsymmetric ditin, Bu3Sn‐SnPh3, was first synthesized by this reductive method.
Differential Cross Sections for the F + H2 Reaction: A Comparison of Classical Trajectory Results for Two Potential Energy Surfaces
Authors: Budenholzer Frank E. , Lin Miao‐Chuan 
Published: May 2015

AbstractClassical trajectories were calculated for the F + H2 reaction over two potential energy surfaces: (1) the well known Muckerman 5 surface (Theoretical Chemistry: Advances and Perspectives 1981, 6A, 1) and (2) the recent surface of Stark and Werner (J. Chem. Phys. 1996, 104, 6515). Integral cross sections, state specified cross sections, differential cross sections and product energy distributions were calculated for the two surfaces. Since the methods for calculating the trajectories and expressing differential cross sections were identical for both surfaces, the rather substantial differences in the results are clearly due to differences in the potential surfaces. The results are discussed in terms of the special characteristics of the two surfaces.
Kinetic Study of S. griseus Aminopeptidase by Stopped‐Flow Fluorescence Energy Transfer
Authors: Yu Hsien‐Cheng , Lin Wann‐Yin 
Published: May 2015

AbstractThe stopped‐flow fluorescence traces for the hydrolysis of Leu‐Ala‐DED catalyzed by Streptomyces griseus aminopeptidase isolated from pronase exhibits a two‐phase fluorescence change with comparable rates of formation and breakdown of the ES complex. We have developed a method for the determination of the individual rate constants from the stopped‐flow traces. The kinetic parameters for the enzyme‐catalyzed hydrolysis of Leu‐Ala‐DED at 25 °C and pH 8.0 are: k1 = (1.6±0.1) × 105 M−1s−1, k−1, = 0.089 ± 0.001 s−1, and k2 = 0.58 ± 0.01 s−1. For the observed stopped‐flow traces, the steady state approximation is valid only within a very small region around the maximal ES concentration and a large proportion (> 20%) of the substrate has already been hydrolyzed during the pre‐steady state. For a very fast formation of ES complex, the steady state approximation is valid for almost the entire trace. The activation energies for each individual rate constant were determined to be 10.0 ± 0.7, 35 ± 5, and 21.2 ± 0.8 kcal mol−1 for k1, k−1, and k2, respectively. Binding of E and S to form ES was accompanied by a decrease in Gibbs free energy, whereas a dramatic increase in free energy was observed for the conversion of ES to ES≠. The dissociation of ES to form E and S had a very large activation energy, but it was also accompanied by a large increase in entropy.
Pulse Perturbation‐Facilitated Optical‐Optical Double Resonance Spectroscopy of the 43σ+g State
Authors: Tsai King‐Li , Whang Thou‐Jen 
Published: May 2015

AbstractTwenty‐three rovibronic levels of the Na2 43σ+g state were observed by pulse perturbation‐facilitated optical‐optical double resonance (PFOODR) excitation spectroscopy through the A1σ+u‐b3πu, mixed intermediate levels. The molecular constants and the Rydberg‐Klein‐Rees (RKR) potential energy curve of the 43σ+g state are derived in this work.
Bonding Nature in Photoelectron Spectra of the Molecules XY2
Authors: Chen Erh‐Hao , Chang Tse‐Chiang 
Published: May 2015

AbstractThe vibrational structures of photoelectron spectra can reveal the bonding nature of molecular orbitals. For diatomic molecules the bonding nature of molecular orbitals can be rationalized by the concepts of non‐bonding lone pair type and bonding type bond orbitals consisting of Lewis structures.For the simplest polyatomic molecules XY2 the concepts of nonbonding lone pair type and bonding type bond orbitals and the method of expanding the canonical molecular orbitals into the bond orbitals are not quite appropriate.Two correlation diagrams, the distance correlation diagram and the angle correlation diagram, provide us with a better theoretical tool. The molecular orbital with the energy curve having positive slope in the distance correlation diagram (or angle correlation diagram) is identified as the R‐bonding (or 9‐bonding) orbital. The removal of an electron from the R‐bonding (or θ‐bonding) gives rise to vibrational excitation with decreasing frequency for the bond stretching (or bending) mode in the photoelectron spectra.
Dehydration of CuSO4 5H2O Studied by Thermo‐Raman Spectroscopy
Authors: Chang Hua , Huang Pei Jane 
Published: May 2015

AbstractIn this work, Raman spectra were taken continuously from CuSO4‐5H2O powders during a dehydration process at temperatures up to 400 °C. The spectra showed the variation in structures for both SO42 and H2O. Furthermore, the band positions, band intensities, and their derivatives also showed these variations in structure and the amount of each component. From the intensities of the OH bands the amounts of water lost were found to be 2:2:1 in three stages as indicated by TGA/DTA. This method of monitoring variations in structure by Raman spectroscopy as a function of temperature can identify individual species and could be important to the study of a material's thermal properties.
Sydnone Complexes of Pentacyanoferrate(II)
Authors: Shi Cheng‐Hsiang , Wang Shiao‐Tsun , Yang Shiao‐Yun , Yeh Andrew , Tien Hsien‐Ju 
Published: May 2015

AbstractThe 3‐methylsydnone (CH3Sd) and 3‐phenylsydnone (PhSd) complexes of pentacyanoferrate(II) were prepared in aqueous solution by the reaction of Fe(CN)5OH23− with excess ligand. Metal to ligand charge transfer transitions were observed for both complexes at 442 nm (CH3Sd) and 494 nm (PhSd), respectively. The reduction potentials were measured with the Ef values of 0.65 and 0.67 V (vs. NHE) for CH3Sd and PhSd, respectively, at 25 °C, μ = 0.10 M LiClO4 and pH = 5. The kinetics of the substitution reaction were also investigated, and kf and kd values (25 °C, μ = 0.10 M LiClO4,pH = 5) are (5.4 ± 0.2) × 10−2M−1s−1 and (1.4 + 0.1) × 10−5s−1 (CH3Sd), (8.8 ±0.1) × 10−2M−1s−1 and (4.7 ±0.1) × 10−5s−1 (PhSd). The kf values for both sydnone complexes are approximately four orders of magnitude smaller than other pentacyanoferrate(II) complexes with neutral ligands. The difference may arise from the mesoionic character of the sydnone compounds rather than via a different reaction mechanism. Spectroscopic, kinetic and electrochemical results all suggest that the sydnone ring shows a better π‐backbonding stabilization with Fe(CN)53− moiety than that of the pyridine ring.
Peroxycoumarins from the Root Bark of Zanthoxylum schinifolium
Authors: Tsai Ian‐Lih , Lin Wei‐Yu , Chang Chin‐Teng , Chen Ih‐Sheng 
Published: May 2015

AbstractTwo new peroxyterpenyl coumarins including peroxyschininallylol [7‐(3′, 7′‐dimethyl‐6′‐hydroperoxyocta‐2′, 7′‐dienyloxy)‐8‐methoxy coumarin] and peroxyschinilenol [7‐(3′, 7′‐dimethyl‐7′‐hydroperoxyocta‐2′, 7′‐dienyloxy‐8‐methoxy coumarin] were isolated from the chloroform‐soluble part of the root bark of Zanthoxylum schinifolium. The structures of these compounds were elucidated by spectral analyses.
Dihydrofolate Reductase from E. coli Catalyzes the Oxygen‐Dependent Oxidation of NADPH in the Absense of Folates
Authors: Hsu Ming‐Ching , Ho Yuh , Huang Fu‐Yung 
Published: May 2015

AbstractThe intensity changes of proton NMR resonances of NADPH and NADP+ were employed to monitor the oxidation of NADPH in the presence of dihydrofolate reductase (DHFR) from Escherichia coli. It was found that in addition to the normal reductase activity E. coli dihydrofolate reductase (DHFR) also catalyzes oxygen‐dependent oxidation of NADPH to NADP+ in the absence of folate or dihydrofolate. Mutant‐type DHFR (Asp27→Asn) shows almost no activity at pH 7.0, while at pH 4.0 it regains its activity. This enzymatic activity is characterized by a fast initial rate followed by a gradual leveling‐off (slow phase), which appears to be due to the depletion of oxygen in the solution, under our experimental conditions. From the NADP concentration at the fast phase we estimated that four moles of NADPH were oxidized per mole of oxygen consumed. The specific activity, determined from the initial rate of NADPH oxidation, is highly pH dependent. It decreases from 9.6 × 10−3 units/mg protein at pD = 5.2 to 0.56 × 103 units/mg at pD = 8.0 at 21 °C. The pH dependence fits quite well to a titration curve of a single group with pKa = 6.5. DHFR inhibitors, trimethoprim (TMP) and methotrexate (MTX) completely inhibit this activity, whereas folate and H4F do not. NADP+ appears to partially inhibit this reaction. Thus this oxidative activity of DHFR shares several similar characteristics of the normal reductase activity and suggests some common structural requirements.
Electrochemistry of Hypervalent Compounds. 6. Selective α‐Fluorination of Sulfides Using Electrogenerated Hypervalent p‐Methoxyiodobenzene Difluoride1
Authors: Fuchigami Toshio , Fujita Toshiyasu , Higashiya Seiichiro , Konno Akinori 
Published: May 2015

AbstractAnodically generated hypervalent p‐methoxyiodobenezene difluoride reacted with α‐(ary]thio)‐ and α‐(benzylthio)acetates, and α‐(phenylthio)acetophenone to provide the corresponding fluorinated compounds. In ail cases, a fluorine atom was introduced exclusively α to the ester or benzoyl group.
Synthesis of Carbon‐Chain Tethered Bistetraoxa‐Cage Compounds
Authors: Chem Jyh‐Haur , Wu Hsien‐Jen , Wang Sue‐Lein , Liao Fen‐Ling 
Published: May 2015

AbstractCarbon‐chain tethered bistetraoxa‐cage compounds 7a‐c and 8a‐c were synthesized from 2‐methylfuran in a four‐step sequence. They were obtained from ozonolysis of the syn bisadducts 5a‐c and the anti bisadducts 6a‐c in dichloromethane at −78 °C followed by reduction with dimethyl sulfide. The structure of the anti bisadduct 6a was proven by X‐ray crystallographical analysis.
Solvolysis of 1‐Aryl‐1‐tert‐butylmethyl Chlorides. Solvent Effects on the Hammett‐type Correlation Analysis
Authors: Liu Kwang‐Ting , Duann Yeh‐Fang , Yu Der‐Gann 
Published: May 2015

AbstractA series of 1‐aryl‐1‐tert‐butylmethyl chlorides were prepared, and their rates of solvolysis in a variety of solvents were measured. Correlation analyses using the single‐parameter Grunwald‐Winstein equation against YBnCl showed excellent linear relationships in every case. Hammett‐type analysis of rate data against Brown‐Okamoto's σ+ constants gave excellent linear correlations with ρ values dependent upon the range of substitutents and the type of solvents used. Similar results were observed when the Yukawa‐Tsuno equation was employed. The use of solvent‐dependent σ+ constants also yielded comparable results, although with smaller variation. The function of solvents on the solvolytic mechanism was discussed.
Thermal Reactions of N‐Acyl Phenylcyclobutylimines
Authors: Wu Pei‐Lin , Chen Chang‐Fu 
Published: May 2015

AbstractFlash vacuum thermolysis of the parent and phenyl substituted N‐acyl cyclobutylimines 3 was under investigation. At 500 °C and 0.01 torr, 3d with phenyl group on C‐1 and 3e with phenyl group on C‐2 of cyclobutane ring underwent ring expansion processes to produce N‐acyl 1,2,3,4‐tetrahydropyridines 8d and 8e. Meanwhile the parent N‐acyl cyclobutylimines 3a together with the phenyl group on C‐3 (3c) and imine carbon (3b) proceeded a hydrogen shift reaction to afford N‐acylaminomethylenecyclobutanes 8a‐c. In addition, cycloreversion competed with ring expansion or hydrogen shift in all cases.
Reactions of 6‐Tricyanovinyldihydroquinolines
Authors: Lin Wen‐Chung , Lin Shaw‐Tao , Hsieh Mon‐Lin 
Published: May 2015

AbstractReactions of 6‐tricyanovinyldihydroquinoline with concentrated hydrochloric acid and methanolic sodium hydroxide yield chlorine substitution on the heterocyclic ring and methoxide substitution of the cyano group, respectively. The chlorine substitution via a radical process is initiated from the tricyanovinyl group by the irradiation of visible light.
Reaction Dynamics and Molecular Spectroscopy Via High Resolution Laser Techniques
Authors: Vetter R. 
Published: May 2015

AbstractLaser techniques are used to enlarge the range of application of crossed‐beam experiments and to increase their resolution, via excitation of atomic/molecular reagents on well‐defined quantum states and characterization of reaction products by L.I.F. and R.E.M.P.I. Detailed applications are described in the case of the Cs + H2 → CsH + H photochemical reaction for which a complete set of experimental data was obtained and interpreted by quasi‐classical trajectories.To apply these techniques precise spectroscopic data are required, which are obtained from high resolution, Doppler‐free beam experiments. In turn, reaction dynamics experiments provide out‐of‐equilibrium light sources which can be used to extend spectroscopic analyses. It is shown how the high resolution study of the TiO molecule leads to a new description of its electronic structure.
Integration of Separation Capillary with a Au Film Electrode and an Etched Decoupler in Amperometric Capillary Electrophoresis
Authors: Chen Der‐Chang , Hsieh Re‐Ming Ray , Chen Chun‐Hsien 
Published: May 2015

AbstractIntroduced in this article is fabrication of an integrated capillary for the applications of electrochemical detection in capillary electrophoresis. The separation section, voltage decoupler, and working electrode were composed into a single section of capillary. The porous decoupler was constructed by HF etching till the thickness of the capillary wall less than 20 μm. The working electrode was prepared by sputtering Au‐films on the outlet of the capillary. The integration of the separation capillary with a complete detection assembly improves the convenience for the routine application of electrochemical measurements in capillary electrophoresis. For a 100‐μm‐i.d. capillary, the theoretical plate number of catechol and the migration time reproducibility can reach 120,000 and 1.9% RSD, respectively. The linear range exceeds 3 order of magnitude and the detection limit is lower than 0.65 μM.
Syntheses, Structures and Spectroscopic Studies of Quadruply Bonded Complexes Containing Bridging Acetate and η3‐etp Ligands (etp = Ph2PCH2CH2P(Ph)CH2CH2PPh2)
Authors: Suen Maw‐Cherng , Chiang Shih‐Fu , Chen Jhy‐Der , Chern Shuenn‐Shing , Hsiao Chwan‐Deng 
Published: May 2015

AbstractThe quadruply bonded complexes containing bridging acetate and polydentate phosphine ligands of the type Mo2(O2CCR3)XJ(η3‐etp) (R = H, X = Br, 1; R = F, X = CI, 2; R = F, X = Br, 3; etp = Ph2PCH2CH2P(Ph)CH2CH2PPh2) were prepared by reactions of Mo2(O2CCR3)X2(PPh3)2 with etp in CH2X2. Their UV‐vis and 31P{1H}‐NMR spectra have been recorded, and the structure of 1 has been determined by X‐ray crystallography. Crystal data for 1·2CH2Br2: space group P21/c, a = 13.924(7) Å, b = 21.157(4) Å, c = 14.427(5) Å, β = 101.82(3)°, V = 4159(2) Å3, Z = 4, with final residuals R = 0.0797 and Rw = 0.0793. The absorption wavelengths of the δ → δ* transitions and the chemical shifts and the coupling constants of the 31P{1H}‐NMR spectra of these complexes are dependent on the natures of the halogen atoms and the acetate ligands.
New Cantharidinimides from Cantharidin and 2‐Arylethylamines: Efficient Synthesis under High Pressure
Authors: Lin Pen‐Yuan , Shi Sheng‐Jie , Hsu Feng‐Lin , Chen Chieh‐Fu 
Published: May 2015

AbstractThe new cantharidinimides 3a‐j were prepared, in good to excellent yield, by heating the reactents 1 and 2a‐j to 200 °C with toluene and triethylamine in a high pressure tube. The mixture was evaporated to dryness and furthermore heated to 180 °C‐200 °C for 1 h.
Studies on the Synthesis of Ethylene Copolymers and Their Properties
Authors: Jiang George J. , Wang Ta‐Yong 
Published: May 2015

AbstractThe copolymerization of ethylene and 5‐ethylidene‐2‐norbornene (ENB) catalyzed by metallocene catalysts system is reported in this paper. The catalysts include Et(Ind)2 ZrCl2/MAO and Cp2ZrCl2/MAO. The resulting copolymer contains an ethylidene group which can be readily converted to a hydroxyl group by hydrogen borane. Then the hydroxyl group in turn can be utilized for grafting with ϵ‐caprolactone. The dependence of the graft weight percentage on the reaction time was also studied. The graft copolymer is a compatibilizer for various polyethylene blends with engineering plastics.A functional polyethylene can be easily synthesized by the copolymerization of ethylene and 9‐decen‐l‐ol using a homogeneous catalytic system of El(Ind)2ZrCl2/MAO. The resulting functional polyethylene was characterized by NMR, DSC, IR and TGA; and can also be utilized for grafting with ϵ‐caprolactone. The grafted copolymer is also an effective compatibilizer.
Syntheses and Characterization of Organoimido Complexes of Niobium(V); Potential CVD Precursors
Authors: Chiu Hsin‐Tien , Lin Jyh‐Cherng , Chuang Shiow‐Huey , Lee Gene‐Hsiang , Peng Shie‐Ming 
Published: May 2015

AbstractNew niobium imido complexes (RN)Nb(NEt2)3 (R = Prn, Pri and But), potential precursors to grow niobium containing thin films by chemical vapor deposition (CVD), were prepared by reacting the corresponding (RN)NbCl3py2 complexes (R = Prn, Pri and But; py = pyridine) with LiNEt2 in hydrocarbon solvents. The structures of (RN)NbCl3py2 (R = Pri and But), determined by X‐ray crystallography, are mononuclear with distorted octahedral geometries, For each complex, three chloride ligands are cis to the imido ligand and occupy meridional positions. One of two py ligands is cis to and the other is trans to the imido ligand. For (PriN)NbCl3py2, the Nb=NPri bond distance (Å) is 1.733(3) and the ∠Nb=N‐Pri angle (°) is 178.0(3). Crystal data: monoclinic, space group P21/n, a = 8.805(2), b = 14.930(4), c = 13, 407(3) Å, β = 93.37(2)°, V = 1759.5(7) Å3, Z = 4, Dc = 1.565 g cm3. For (ButN)NbCl3py2, the Nb=NBut bond distance (Å) is 1.734(4) and the ∠Nb=N‐Bul angle (°) is 174.8(4). Crystal data: monoclinic, space group P21/c, a = 9.609(1), b = 13.591(6), c = 14.615(2) Å, β = 90.05(1)°, V = 1908.5(9) Å3, Z = 4, Dc = 1.492 g cm−3.
A Stereoselective Preparation of 1,2,7‐Triazabicyclo[3.3.0]oct‐2‐enes
Authors: Teng Ju‐Tsen , Yang Chia‐Hsi 
Published: May 2015

Abstract5‐(Alkylamino)methyl‐2‐pyrazolines react with ketones or aldehydes to give 1,2,7‐triazabicyclo‐[3.3.0]oct‐2‐enes in high yields. The reaction gives only one diastereomer with various aldehydes, except for CH3CHO.
Spectrophotometric Determination of Rhenium(IV) with Thiocyanate, TX‐100 and N,N′‐Diphenylbenzamidine
Authors: Agnihotri P. K. , Deb M. K. , Thakur Manisha , Mishra R. K. 
Published: May 2015

AbstractA spectrophotometric method to determine rhenium(IV) at trace level is based on the extraction of Re(IV)‐SCN− complex in sulphuric acid media with N,N′‐diphenylbenzamidine(DPBA) in presence of a non‐ionic surfactant triton X‐100 (TX‐100) in chloroform. The complex shows maximum absorbance at 435 nm with amolar absorptivity value of 4.24 × 104 L mol−1 cm−1 at an acidity range 3.5‐6.5 M H2SO4. The method followed Beer's Law for the system Re(IV)‐SCN−(TX‐100)‐DPBA upto 4.0 μg Re(IV) mL−1. The detection limit of the method is 5 ppb. None of the tested foreign ions, except molybdenum(VI), interfere with the determination of rhenium. The interference due to molybdenum could effectively be removed by prior precipitation with oxine. The effect of various analytical parameters on the extraction of the metal are discussed.