bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Phases Formed by the Dehydration of Disodium Zirconium(IV) Bis(orthophosphate) Trihydrate and Their Ion-exchange Behavior
Authors: Inoue Yasushi , Yamada Yoshimune 
Published: July 2006

Abstract
The phase transformation of Na2Zr(PO4)2·3H2O which had been obtained from zirconium(IV) bis(hydrogenphosphate) monohydrate(α-zirconium phosphate), prepared by the direct precipitation method, was studied by means of gravimetry, X-ray analysis, and acid-base titration. When the material was heated for 2 d, it was transformed to a monohydrate at 80 °C and then successively to three anhydrous phases, depending on the temperature. The monohydrate was also formed by letting the trihydrate stand over P2O5 at room temperature for longer than two weeks. The processes were confirmed to be irreversible by an examination of the rehydration behavior, from which the conditions of the storage of five modifications of disodium zirconium(IV) bis(orthophosphate) were established. It is of special interest that the second anhydrous phase reverted to the first one when it was allowed to stand at room temperature in air or in a desiccator. The rate of the reversion decreased with the temperature of heat-treatment and with a decrease in the relative humidity of the surroundings. The difference between the present results and Clearfield’s was clarified and attributed mainly to the difference in the crystallinity of the starting α-zirconium phosphate.
A Ruthenium(IV)-Ruthenium(III) Dimer, Product of the Reaction of Aqua(ethylenediaminetetraacetato)ruthenium(III) with Chlorate Ions
Authors: Ikeda Masato , Shimizu Kunio , Satô Gen P 
Published: July 2006

Abstract
An oxo-bridged, mixed-valence complex of ruthenium(IV,III), [(edta)RuIVORuIII(edta)3−, has been obtained from the oxidation of [RuIII(edta)(H2O)]− by chlorate ions. The formulation of the complex as a μ-oxo dimer of ruthenium(IV,III) is based on the results of a variety of experiments, including elemental analyses, magnetism, by spectrophotometry, and by electrochemical studies. These studies in acetate buffer solution show that the dimeric ion can be reduced at mercury electrode to [(edta)RuIIIORuIII(edta)]4− and then is monomerized to the original [Ru(edta)(H2O)]− in a fast reaction.
Photoreaction of Tris(ethylenediamine)cobalt(III) Ion with Bis(2-hydroxyethyl)dithiocarbamate Ion
Authors: Nakashima Michio , Kida Sigeo 
Published: July 2006

Abstract
Complete ligand replacement of tris(ethylenediamine)cobalt(III)([Co(en)3]3+) by bis(2-hydroxyethyl)dithiocarbamate ion(htc−) forming [Co(htc)3] is induced by visible light in aqueous solution. The quantum yield of the reaction depends on the wavelength of the light and on the concentrations of the complex and the ligand. The distinct feature of this photo-induced substitution is that the quantum yield is higher than unity for the solution containing 0.02 mol dm−3 [Co(en)3]3+ and 0.13 mol dm−3 htc−. The unusually high quantum yield is explained on the basis of a primary photoredox process followed by a chain reaction involving cobalt(II) species as chain carriers. Cobalt(III) complexes of an N6 donor set such as [Co(NH3)6]3+, [Co(NH3)4(pn)]3+, [Co(chxn)3]3+, and [Co(dien)3]3+ also undergo similar photo-reaction, where pn, chxn, and dien denote 1,2-propanediamine, 1,2-cyclohexanediamine, and diethylenetriamine, respectively.
Preparation and Conformational Properties of Several 1,8-Diarylnaphthalenes
Authors: Ibuki Eiichi , Ozasa Shigeru , Fujioka Yasuhiro , Mizutani Hiroshi 
Published: July 2006

Abstract
Six new 1,8-diarylnaphthalenes, each having closely held parallel aromatic rings, were synthesized by a Kharash-type Grignard cross-coupling of arylmagnesium iodide and 1,8-diiodonaphthalene in the presence of N,N′-bis(1-methyl-3-oxobutylidene)ethylenediaminatonickel(II) as a catalyst. Among them, 1,8-di(1-naphthyl) naphthalene was obtained as cis and trans rotamers, caused by the restricted rotation at the 1,8-position. Interconversion between the rotamers on heating above their melting points was confirmed by differential scanning calorimetry. The proton magnetic resonance spectral studies of the 1,8-diarylnaphthalenes indicated the presence of a face-to-face arrangement of aromatic rings in the peri-position. Two new 8,8′-diaryl-1,1′-binaphthyls, each having two sets of closely held parallel aromatic rings, were isolated as minor coupling products. Trans-trans conformations were proposed for them on the basis of their thermal behavior. Several nickel(II) complexes were found to be effective catalysts for preparative Grignard cross-coupling reaction involving closely crowded geometry.
Direct Observation of the Rate for Cis→Trans and Trans→Cis Photoisomerization of Stilbene with Picosecond Laser Photolysis
Authors: Sumitani Minoru , Yoshihara Keitaro 
Published: July 2006

Abstract
The rates for direct cis→trans and trans→cis photoisomerizations of stilbene in solution were measured with a newly developed monitor light source for picosecond laser photolysis in the UV region. The rate constant of the trans→cis isomerization is 1.2×1010 s−1 in hexane at 295 K. The fluorescence decay rate constant of the S1 state of trans-stilbene has the same value. Thus, the decay of the S1 state is the rate limiting step and the lifetime of an intermediate perpendicular state (1p) has to be very short. The cis→trans isomerization is very fast and the half life of the excited cis-isomer is less than a few picosecond. These observations strongly indicate that the isomerization reaction proceeds through the potential surface of the singlet excited states.
Nickel(0) Catalyzed [2+2] Cross-addition of Bicyclo[2.2.1]heptene Derivatives with Electron-deficient Olefins
Authors: Takaya Hidemasa , Yamakawa Masashi , Noyori Ryoji 
Published: July 2006

Abstract
In the presence of bis(acrylonitrile)nickel(0) or bis(1,5-cyclooctadiene)nickel(0), exo-tricyclo[3.2.1.02,4]oct-6-ene cycloadds to acrylonitrile and methyl acrylate to give anti- and syn-3-cyano-exo,exo-tetracyclo[4.3.1.02,5.07,9]decane or the corresponding methoxycarbonyl derivatives. The cycloaddition with dimethyl maleate proceeds with retention of configuration. Benzonorbornadiene also enters into the 2+2 reaction, while endo-tricyclo[3.2.1.02,4]oct-6-ene, bicyclo[2.2.1]heptene, and 5-methylenebicyclo[2.2.1]heptene are unreactive. Origins of the observed selectivities in the catalyzed reaction are discussed.
Reactions of α,N-Diarylnitrones with O-Methyl Diphenylphosphinothioate and Oxidations of N-Alkylidene-2-hydroxyanilines with Silver Oxide. Preparation of Benzoxazoles
Authors: Yoshifuji Masaaki , Nagase Rihei , Inamoto Naoki 
Published: July 2006

Abstract
Reactions of α,N-diarylnitrones in the presence of O-methyl diphenylphosphinothioate at 150 °C gave 2-arylbenzoxazoles (3) in fairly good yields. Oxidation of N-alkylidene-2-hydroxyanilines with silver oxide afforded 2-alkenyl-, 2-alkyl-, or 2-arylbenzoxazoles (7 and 3) in good yields under mild reaction conditions (at room temperature). A plausible mechanism for formation of 3 and 7 has been discussed briefly.
An X-Ray Crystallographic Study on cis-trans Configurational Assignment to “cis-” and “trans-1,8-Terpins” and a Proposal of New Designation for Discriminating between the Configurational Isomers
Authors: Suga Takayuki , Hirata Toshifumi , Aoki Tadashi 
Published: July 2006

Abstract
The crystal structures of “cis-terpin” (terpin hydrate) and “trans-terpin” were elucidated by X-ray crystallography. This crystal structure elucidation showed that the hydroxyl group at C-1 and the 1-hydroxy-1-methylethyl group at C-4 are in cis and trans relationships in the “cis-” and “trans-1,8-terpin” molecules, respectively, similarly to the structures in solutions. A new designation for discriminating between the configurational isomers is proposed on the ground of the IUPAC Rule for Nomenclature.
Alkaline Hydrolysis of Propella-δ- and ε-lactones
Authors: Kakiuchi Kiyomi , Tobe Yoshito , Odaira Yoshinobu 
Published: July 2006

Abstract
Second-order rate constants for the alkaline hydrolysis of a series of propella-δ- and ε-lactones at 32.3 °C have been determined. The conclusion to be drawn from the kinetic data is as follows. In the case of propella-δ-lactones, the steric effect of the third ring on the hydrolysis plays an important role, whereas the hydrolysis of propella-ε-lactones is mainly governed by the steric effect attributable to the flexibility of the ε-lactone ring, and, on the contrary, the steric effect of the third ring is of no great consequence.
Coenzyme Models. 30. On the Unusual Spectroscopic Behaviors of Amphiphilic Flavins and 5-Deazaflavins
Authors: Shinkai Seiji , Harada Akiko , Manabe Osamu , Yoneda Fumio 
Published: July 2006

Abstract
At room temperature in aqueous solution, isoalloxazines and 5-deazaisoalloxazines with 10- dodecyl substituent gave a well-resolved, three-banded Sl peak which has been believed to appear only in nonpolar solvents or in enzymic hydrophobic pockets where isoalloxazines and 5-deazaisoalloxazines become free of hydrogen-bonding effects. On the other hand, 3-methyl-10-ethylisoalloxazine and 5-deazaisoalloxazines with 10- ethyl or 10- octyl group did not give such a fine-structured Sl peak. We have found that (i) the fine structure disappears on the addition of organic solvents (ethanol&gt;40 vol% or pyridine&gt;20 vol%), (ii) the fine structure also disappears on the addition of surfactants (CTAB, Brij-35, and SDS) above the critical micelle concentrations, (iii) 10-dodecylisoalloxazine with hydrophilic 3-(thiazolinio)propyl group at 3-position has not the fine structure, and (iv) the fluorescent intensity of 3-methyl-10-dodecyl-5-deazaisoalloxazine is much weaker than that of 3-methyl-10-ethyl-5-deazaisoalloxazine in aqueous solution but these intensities become comparable above 40 vol% ethanol. These findings are consistently rationalized in terms of an aggregation-deaggregation equilibrium of amphiphilic flavin analogues, supporting that the fine structure in aqueous solution is due to the “stacking” association of (5-deaza)isoalloxazine nuclei, like that of dye molecules. The aggregation-deaggregation phenomenon is sensitively reflected by the reactivity: the reaction of 3-methyl-10-ethyl-5-deazaisoalloxazine and cyanide ion gave k2=1.27 M−1 s−1 in aqueous solution at 30 °C, whereas aggregated 3-methyl-10-dodecyl-5-deazaisoalloxazine did not react with cyanide ion. These findings have significant implications on the chemistry of flavoproteins, because the absorption spectra of enzyme-bound flavins and 5-deazaflavins have frequently been cited to discuss the flavin reactivities.
Infrared Study of 12-Molybdophosphoric Acid Reduced by Organic Compounds
Authors: Tsai Tian-hsi , Maruya Ken-ichi , Ai Mamoru , Ozaki Atsumu 
Published: July 2006

Abstract
Reaction of 12-molybdophosphoric acid with ethyl methyl ketone, crotonaldehyde, methacrylaldehyde, 1-butene, or 1,3-butadiene is enhanced by the presence of water, and leads to preferential decrease in ν(P–O) at 1060 cm−1 with preference over that in ν(Mo–O–Mo) at 880 cm−1, while the reaction with methanol is not dependent on the presence of water and results in rapid disappearance of ν(Mo–O–Mo) and retention of ν(P–O).
Recovery of Heavy Metals with Calcium Silicon Alloy. II. Recovery of Copper(II) Ions
Authors: Tokunaga Shuzo 
Published: July 2006

Abstract
In the 20.0-matom dm−3 Cu(II) solution of an initial pH of 4.0, more than 99% of it was removed by addition of calcium silicon alloy in ca. 5 min, and the pH decreased to below 2. The X-ray diffraction pattern of the solid reaction product indicated that the Cu(II) removal took place through reduction to metallic Cu. In the 1.0-matom dm−3 Cu(II) solution, the pH increased from 4.0 to above 9.0 in 30 min, which consequently maintained high removal for a long time. In the constant pH runs, relation of the equivalents of Ca and Si dissolved against that of Cu(II) ions removed showed that not only the Ca moiety but also the Si moiety participated in the reduction of Cu(II) ions. It is desirable to control pH value at 3.0 or higher, or to separate the solid phase from the liquid phase in the first 30–60 min in order to avoid excess dissolution of calcium silicon alloy and to attain high Cu(II) removal. Copper(I) oxide was formed in a solution of pH above ca. 5, which was in contact with the air. In a HNO3 solution, the removal decreased considerably. Sodium nitrate also caused strong interference with the removal which can be prevented by acidifying the solution with HCl to pH ca. 1. When Hg(II) or Cr(VI) ions are present, the Cu(II) removal tends to decrease depending on the amount of calcium silicon alloy added.
The Effect of Pressure on the Mutual Solubility of a Nonionic Surfactant–Water System
Authors: Kaneshina Shoji , Shibata Osamu , Nakamura Makoto 
Published: July 2006

Abstract
The cloud-point temperature (T) of an aqueous hexa(oxyethylene) dodecyl ether solution was determined as a function of the pressure (P) and the composition (x2). The volume (ΔV) and entropy (ΔS) changes for the separation of the surfactant phase from the water phase were estimated from the T-P-x2 relation. Both ΔV and ΔS were positive.
The Nafion-H-catalyzed Acylation of Thiophene with Acid Anhydrides
Authors: Konishi Hisatoshi , Suetsugu Kazuhiro , Okano Tamon , Kiji Jitsuo 
Published: July 2006

Abstract
The reaction of thiophene with acyclic acid anhydrides in the presence of Nafion-H (fluorocarbon resin sulfonic acid) afforded the corresponding 2-acylthiophenes in moderate yields. Acylation with cyclic acid anhydrides gave only low yields, however. The Nafion-H catalyst could be reused for the acylation with a little loss of activity.
The Enantioface-differentiating Methylation of the N-Benzylidene-Dl-phenylalanine Methyl Ester in the Presence of Chiral Lithium Amides
Authors: Yamashita Tetsushi , Mitsui Hitoshi , Watanabe Hiroyuki , Nakamura Nobuo 
Published: July 2006

Abstract
The asymmetric methylation of the N-benzylidene-Dl-phenylalanine methyl ester was carried out in the presence of lithium salts of secondary amines derived from (S)-proline. The lithium amides of poly(imino-1-isobutylethylene) and its corresponding low-molecular-weight model compound, derived from (S)-leucine, were similarly used in order to examine the polymer effects with regard to the stereoselectivity.
Hydrothermally Activated Silica–Alumina. II. Variations in Catalytic Activities for 1-Butene Isomerization and Polymerization, and in the Amount of Acid with Pretreatment Temperature
Authors: Furuyama Shozo , Murashita Osamu , Ichisaka Kotomasa , Morimoto Tetsuo 
Published: July 2006

Abstract
The technique of hydrothermal activation was used to prepare well-mixed and fully hydroxylated silica–alumina catalysts, SA-nMHT (n=13, 25, or 50 denotes the alumina content (wt%)). Their catalytic activities and cis/trans selectivities for the 1-butene isomerization (ki and c/t), the catalytic activities for the 1-butene polymerization (kp), the amount of acid (A), and the number of the surface hydroxyl group (NOH) were measured as a function of the degassing temperature (Td) over the 25–700 °C range; the following results were obtained: (1) ki changed prominently with Td and reached its maximum around 300 °C. (2) c/t was about 0.9 below 500 °C, but exceeded 1.2 at 700 °C. (3) kp increased till 300 °C and became constant above that temperature. (4) A was almost independent of Td above 100 °C. (5) NOH decreased from 11–15 (at 100 °C) to 0.5 group nm−2 (at 700 °C). An analysis of these data led to the conclusion that the SA-nMHT sample underwent the surface structural changes three times during the thermal dehydroxylation between 25 and 700 °C. The sequence of the structural change was sketched, and the different dependencies upon Td of ki, kp, and A were explained.
Molecular Structures of [2](2,5)(7,7,8,8-Tetracyanoquinodimethano)[2]paracyclophane and 14,17-Dimethoxy[2](2,5)(7,7,8,8-tetracyanoquinodimethano)[2]paracyclophane
Authors: Mizuma Takashi , Matsuura Hideaki , Kai Yasushi , Yasuoka Noritake , Kasai Nobutami 
Published: July 2006

Abstract
The molecular structures of two [2.2]paracyclophanes containing a 7,7,8,8-tetracyanoquinodimethan (TCNQ) moiety as an electron acceptor have been determined by means of X-ray diffraction. The electron-donating moieties in these cyclopahnes are benzene (TCNQ-X) and p-dimethoxybenzene (TCNQ-X (OMe)2) rings. TCNQ-X crystallizes in a triclinic space group P\bar1 with two molecules per unit cell; a=9.772(2), b=18.477(4), c=6.569(1) Å, α=90.38(2), β=107.92(2), γ=100.32(2)°. The crystals of TCNQ-X(OMe)2 belong to the orthorhombic system; space group Fdd2; a=25.618(3), b=31.895(5), c=9.808(1) Å, Z=16. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure to R=0.088 (TCNQ-X) and 0.109 (TCNQ-X(OMe)2) for 3141 and 1695 non-zero rehections. In the two structures determined, the [2.2] paracyclophane skeleton has the usual structure; the benzene ring and six-membered ring of the TCNQ moiety have a boat form, and two C(CN)2 portions in the TCNQ moiety are bent down from the mean plane defined by the C(12), C(13), C(15), and C(16) atoms.
Phase Transitions in Tetramethylammonium Hexachloroplatinate(IV), -tellurate(IV), and -stannate(IV) as Studied by 35Cl NQR and Powder X-Ray Diffraction
Authors: Furukawa Yoshihiro , Prabhumirashi Laxman S , Ikeda Ryuichi , Nakamura Daiyu 
Published: July 2006

Abstract
The 35Cl NQR spectra of [(CH3)4N]2PtCl6, [(CH3)4N]2TeCl6, and [(CH3)4N]2SnCl6 were recorded in a temperature range between 77 and ca. 350 K. Below room temperature, the temperature dependence measurements of NQR frequencies for all of these complexes confirmed the presence of structural phase transitions reported very recently. From the experiments of DTA carried out above room temperature, structural phase transitions were located at 385, 351, and 365 K in the same order of the above complexes. The X-ray powder patterns taken in the highest-temperature phase of these complexes (at ca. 390 K) were well interpreted as arising from the K2PtCl6-type cubic structure with the lattice constant a0=12.828, 13.053, and 12.975 Å for the Pt, Te, and Sn complexes, respectively. In this phase of each complex, however, no NQR spectra were observed. The mechanism of the phase transitions detected is discussed in connection with the structure of these complexes.
The Polarization Characteristics and the Thickness of the Catalyst Layers in Fuel Cell Electrodes
Authors: Kenjo Tadao , Nakajima Noriyuki 
Published: July 2006

Abstract
The polarization characteristics of poly(tetrafluoroethylene)-bonded Raney nickel hydrogen- and silver oxygen-electrodes have been measured as a function of the thickness of the catalyst layer, and the polarization curves of these electrodes have been analyzed on the basis of the electrolyte film model. The observed polarization curves were divided into several segments and a linear polarization-current equation, derived from the model, has been applied to each segment. The performance of the electrodes approaches asymptotically to an upper limit with the thickening of the catalyst layers. The profiles of the faradayic current density across the electrode wall have been estimated for both electrodes. In contrast with the almost flat profiles of the Raney nickel electrodes, the current densities for the silver electrodes are localized on the liquid side of the electrodes; a thin area of the catalyst layer ranging from the electrode-face/electrolyte interface to 5.3×10−3cm distance sustains most of the load current at a polarization of 220 mV. The catalytic activities of both the silver and Raney nickel catalysts are enhanced with progression of the polarization while the resistivities of the electrolyte film maintained essentially constant. A slight surface oxidation for the Raney nickel and a surface reduction for the silver catalysts have been suggested as probable explanations for the enhanced catalytic activities observed.
129I Mössbauer Effect in Several π-σ Charge Transfer Complexes of Iodine
Authors: Sakai Hiroshi , Matsuyama Tomochika , Yamaoka Hitoshi , Maeda Yutaka 
Published: July 2006

Abstract
The 129I Mössbauer spectra at 16 K have been measured for the π-σ charge transfer complexes of iodine with benzene, coronene, perylene, and poly(p-phenylene). It is suggested that the benzene-iodine complex in benzene prepared by slow cooling consists of alternate benzene and iodine molecules with the six-fold axial symmetry. The Mössbauer spectrum for the coronene-iodine complex (1:1) shows only one chemical state of iodine. The acceptor orbital is described by only the σu-antibonding molecular orbital of iodine. The extent of charge transfer in the complex is estimated to be 0.06e− in the electronic ground state. In the poly(p-phenylene)-iodine complex the iodine exists as almost a free molecule, indicating that the interaction between the phenylene ring and iodine is very weak.
Conformational Changes of the Poly(α-l-glutamic acid)–Cu(II) Macromolecular Complexes in the pH Range 4–7. A Comparative Study by Means of Viscosity and Circular Dichroism
Authors: Masujima Tsutomu , Yamaoka Kiwamu , Hori Jin-ichiro 
Published: July 2006

Abstract
Intrinsic viscosity, [η], and far-UV circular dichroism, CD, were measured at 25 °C for poly(α-l-glutamic acid), poly(Glu), solutions in 7.5 mM and 150 mM NaCl in the presence and the absence of copper(II) ions over the pH range 4–7, where poly(Glu) undergoes two conformational transitions. The first is the well-known helixcoil transition and the second, which is followed by completion of the helix, was attributed to the formation of aggregates. The pH dependence of [η] and molar ellipticity was analyzed with the two-state model. The helixcoil transition can not be represented by the all-or-none process. The aggregation mode of helices is predominantly the side-by-side type in 7.5 mM NaCl, but probably a mixture of the side-by-side and the head-to-tail types in 150 mM NaCl. The hydrodynamic shapes of poly(Glu) and its Cu(II)-complexes were calculated with ellipsoid, cylinder, and straight chain element models. The so-called random-coil form is an extended-coil in 7.5 mM NaCl at higher pH. The poly(Glu) helix is probably slightly shortened as compared with the α-helix.
A Kinetic Study on the Conformational Change of Bovine Serum Albumin Induced by Sodium Dodecyl Sulfate
Authors: Takeda Kunio 
Published: July 2006

Abstract
Stopped-flow measurements were made on the conformational change of bovine serum albumin induced by sodium dodecyl sulfate in a buffer solution containing 3.33 mmol/dm3 NaH2PO4 and 3.56 mmol/dm3 Na2HPO4 (pH 7.0, μ=0.014). The protein adopted a conformation with a smaller helical content than the original native state (helix to coil transition) upon the addition of the surfactant. The rate of transition depended strongly on the surfactant concentration. The results were compared with those of conformational changes of other proteins, in which a helical structure increased in the surfactant solution (coil to helix transition). It is noticeable that the value of the activation entropy is negative in the helix to coil transition, as compared with its positive and large values in the coil to helix transition. It seems that the binding of the surfactant to the protein causes the transition to only a particular conformation of the protein via each individual process.