bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strontium Immobilization by Fibrous Cerium(IV) Bis(monohydrogenphosphate) under Hydrothermal Conditions
Authors: Hayashi Hiromichi , Ebina Takeo , Onodera Yoshio , Iwasaki Takashi 
Published: June 2006

Abstract
The uptake of strontium ions from an aqueous solution by fibrous cerium(IV) bis(monohydrogenphosphate) has been studied from the viewpoints of the immobilization of strontium in radioactive waste by a batchwise operation in the temperature range from 25 to 250 °C. Strontium ions can be exchanged below 100 °C following an ion-exchange reaction between hydrogen ions of the phosphate groups. In contrast, strontium ions can be effectively immobilized under hydrothermal conditions accompanied by a structural change of the exchanger, where divalent strontium ions are incorporated into the monazite-like compound to compensate tetravalent cerium ions in trivalent cerium orthophosphate system. This phenomenon is peculiar to alkaline earth metal ions, since the monazite-like compounds were obtained in the presence of Ca2+ and Ba2+, while this phenomenon was absent in the presence of Cu2+ or Ni2+.
Theoretical Study of Lithium-Doped Polycyclic Aromatic Hydrocarbons
Authors: Ago Hiroki , Nagata Koji , Yoshizawa Kazunari , Tanaka Kazuyoshi , Yamabe Tokio 
Published: June 2006

Abstract
The interactions between carbon layers and lithium atoms are described with a semiempirical molecular orbital method in order to clarify the Li storage mechanism in amorphous carbon (a-C) materials used in Li ion rechargeable batteries. The general electronic and geometric structures of Li-doped a-C materials are investigated using ovalene (C32H14) as a model carbon structure. The following results are obtained. (i) The intercalation of Li atoms proceeds preferentially up to the C6Li configuration, followed by the absorption of Li atoms on the surface of the carbon layer. (ii) The adsorption of Li atoms can occur even on the nearest neighbor site and can form Li cation clusters commensurate with the carbon lattice. (iii) Li atoms located at the acene-edge sites are more stable than those at the phenanthrene-edge sites. This result suggests that the acene-edge structure is favorable for carbon anode materials. (iv) Substitution of the carbon skeleton by heteroatoms such as boron and nitrogen is not effective for Li storage.
Bethe Surface of Liquid Water Determined by Inelastic X-Ray Scattering Spectroscopy and Electron Correlation Effects
Authors: Watanabe Noboru , Hayashi Hisashi , Udagawa Yasuo 
Published: June 2006

Abstract
By means of inelastic X-ray scattering spectroscopy, the generalized oscillator strength (GOS) of liquid water has been experimentally determined over a range 0.69 ≤ q ≤ 3.59 a.u., where q is the momentum transfer. The Bethe surface was constructed from the GOS, and the loss function, the dielectric response function, and the static structure factor were deduced. It was found that the GOS of liquid water is dominated by individual molecular properties over the q range studied, and that the static structure factor agrees quite well with a calculation including electron-electron correlation effects.
Analysis of Chemical Phenomena by Solving the Constrained Hartree–Fock Equation. III. Influence of Geometry Change on the Energy of π Electrons in Conjugated Hydrocarbons
Authors: Ichikawa Hiroshi , Kagawa Hirotaka 
Published: June 2006

Abstract
The total energy of a conjugated unsaturated hydrocarbon can formally be partitioned into the energy of π electrons and the frame energy. This type of partitioning has been used to study the role of π electrons; to know the relationship between the π-electronic structure and its energy, the molecular geometry has been varied. This paper examines the influences of such geometry change on the energy of π electrons from a basic point of view. It was found that there are four types of geometrical influences which disguise the relationship between the π-electronic structure and its energy. Contrary to this, the constrained Hartree–Fock method was shown to disclose the relationship between π-electronic structure and its energy clearly.
Application of the constrained Hartree–Fock method to D6h and D3h benzenes showed that in a D6h benzene π electrons favor the symmetrically uniform distribution independently of the bond length and the partitioning method, while in a D3h benzene the uniform distribution of π electrons is destroyed. Analysis of gradients of partitioned energies with respect to the bond order at a D3h-distorted benzene indicated that π electrons favor a more uniform delocalization, but this is opposed by one- and two-electron potentials.
Photochromic, Electrochemical, and Photoelectrochemical Properties of Novel Azopyridinium Derivatives
Authors: Nakagawa Masaru , Rikukawa Masahiro , Watanabe Masayoshi , Sanui Kohei , Ogata Naoya 
Published: June 2006

Abstract
Organic photochrome azopyridiniums were systematically prepared by quaternizing azopyridines with either dimethyl sulfate or 1,3-propanesultone. Photochemical, electrochemical, and photoelectrochemical studies on the azopyridiniums as methyl sulfate, hexafluorophosphate, and zwitterionic compounds were carried out in aprotic solvents and in aqueous solutions. The azopyridiniums, which have 3-located quaternized nitrogens to the azo group, exhibited photochemical activity of trans cis isomerization. Quaternization of the pyridine moiety decreased the photochemical conversion between the trans and cis forms. The photochromic properties were influenced by an electronic effect of quaternized nitrogens and an electrostatic interaction of counter anions. In electrochemical studies, new redox-active azopyridiniums were found by using cyclic voltammetry and an electrochemical technique coupled with UV-vis spectroscopy. By the quaternization of azopyridines, the formal reduction potentials were shifted to a positive region up to −0.27 V vs. Fc/Fc+. The reversibility of the electrochemical reactions was strongly dependent on the location of quaternized nitrogen. The trans cis photoisomerization of electroactive azopyridiniums influenced their electrochemical properties. The photochromic molecules exhibited a photoelectric effect, which was a change in the cathodic limiting currents of azopyridiniums, reversibly modulated by ultraviolet light of an external stimulation.
Electrocatalytic Fischer–Tropsch Reactions. Formation of Hydrocarbons and Oxygen-Containing Compounds from CO on a Pt Gas Diffusion Electrode
Authors: Hara Kohjiro , Sonoyama Noriyuki , Sakata Tadayoshi 
Published: June 2006

Abstract
Electrocatalytic reduction of CO under high pressure (&lt; 60 atm) using a gas diffusion electrode containing Pt catalyst (Pt-GDE) has been investigated. Acetic acid was formed at a high faradaic efficiency of 32% as a predominant CO reduction product at a constant current density of 200 mA cm−2 under CO 40 atm. Moreover, methane, ethane, ethylene, formaldehyde, acetaldehyde, ethanol, 1-propanol, and allyl alcohol were produced as CO reduction products. The selectivity of the reduction products depends remarkably on electrolysis conditions such as the current density, pressure of CO, and temperature. C2-compounds such as ethylene, ethanol, and acetic acid were preferentially formed at small current densities and/or high CO pressure conditions, whereas methane was predominantly produced at large current densities and/or low CO pressure conditions.
The Micellar Properties of Ionic Surfactants Consisting of the α,ω-Type Surfactant Ion and the Same Type Counter Ion
Authors: Satake Iwao , Morita Tadakazu , Maeda Tamaki , Hayakawa Katumitu 
Published: June 2006

Abstract
The micellar properties of N,N,N,N′, N′,N′-hexamethyl-1,20-icosanediyldiammonium, or the corresponding di(1-pyridinium)alkanedioates −OOC(CH2)nCOO− (n = 2—10), were studied by conductivity and pyrene fluorescence measurements. In both systems, the critical micelle concentration (cmc) varied little up to n = 4, but decreased rapidly with a further increase in n. The binding degree (β) of the alkanedioate counter ion was virtually independent of the type of surfactant ion head group and gradually increased from 0.69 at n = 2 to 0.91 at n = 10. The observed n dependences of cmc and β were similar to those of the conventional ionic surfactants with an α,ω-type counter ion, indicating the importance of the hydrophobic interaction between the hydrocarbon part of the counter ion and the micellar core. On the basis of a phase-separation model, the transfer free energy per methylene group of the counter ion from aqueous-to-micellar environments was estimated to be about −1.0 RT. The fluorescence measurements suggest that the surface layer of the micelle becomes progressively loose as n decreases. The micelle aggregation numbers of the bis (trimethylammonium) salts are of the order of 50.
Solvent Extraction and Separation Studies of Platinum Using Bis(2-ethylhexyl) Hydrogen Phosphate
Authors: Sherikar Aniruddha V , Phalke Pradeep N , Dhadke Purushottom M 
Published: June 2006

Abstract
The extraction of platinum(II) from hydrochloric acid solution using bis(2-ethylhexyl) hydrogen phosphate in toluene was studied as a function of several variables, such as hydrochloric acid concentration, reagent concentration, metal ion concentration, temperature, effect of various diluents, and effect of various diverse ions. The proposed method was further applied for the separation of platinum from palladium, gold, and osmium in different ratios and to estimate the amount of platinum present in commercially available samples.
Protonation Behavior and Intramolecular Interactions of α,ω-Alkanediaminepolymethylenepolyphosphonates
Authors: Ichikawa Tomohide , Sawada Kiyoshi 
Published: June 2006

Abstract
The protonation equilibria of two types of aminopolyphosphonates ((CH3)2−p(CH2PO3)pN(CH2)mN(CH2PO3)p′(CH3)2−p′) in aqueous solution were investigated by means of potentiometry and 31P NMR spectroscopy. The protonation behavior of diaminotetramethylenetetraphosphonate (p = p′ = 2) is significantly altered by a change in the number of methylene chains (m = 2, 3, 6). The protonations of the imino fragments of hdtmp, which is connected with a six methylene chain (m = 6), are essentially independent of each other, whereas edtmp, which is connected with a two methylene chain (m = 2), forms a hydrogen bond between both nitrogen atoms (NH+···N) in the mono protonated species. The ethylenediaminepolyphosphonates (m = 2), having an iminodiphosphonate group (p = 2, p′ = 0—2), show a peculiar 31P NMR behavior in which the signal shows a downfield shift at higher protonated species. However, eddmp (N,N′), having one methylenephosphonate group at each imino fragment (p = p′ = 1), does not show such an anomaly. These results indicate the existence of an intramolecular interaction between both fragments, such as a hydrogen bond of a protonated nitrogen atom with unprotonated phosphonates of another imino fragment, where two methylenephosphonate groups in one imino fragment are required to operate such an interaction.
Molecular-Dynamics Study of Aqueous Solution of Trehalose and Maltose: Implication for the Biological Function of Trehalose
Authors: Sakurai Minoru , Murata Masashi , Inoue Yoshio , Hino Akihiro , Kobayashi Syouichi 
Published: June 2006

Abstract
Molecular-dynamics simulation of aqueous solution of trehalose and maltose were performed to reveal any difference in the hydration ability between them, and to obtain information about how trehalose protects biological materials from water stress. Here, in order to examine the spatial distribution of water molecules around the hydroxy oxygen of sugar, a two-dimensional pair distribution function was introduced in addition to the conventional radial-distribution function. Both sugars were found to be extensively hydrogen bonded to solvent molecules. However, in a solution of maltose, defective hydrogen bonding was found at the exocyclic hydroxymethyl group of the reducing residue. Thus, maltose has a smaller value in hydration number than does trehalose. The translational diffusion of water molecules around trehalose has been found to be slightly more restrained than that around maltose. These findings are consistent with available experimental data concerning the solution properties of both sugars. On the basis of these results, the functional mechanism of tolerance is briefly discussed.
Reactions of ap- and sp-1-(9-Fluorenyl)-2-(1-methylethenyl)naphthalene Rotamers with Bromine Chloride or Iodine Chloride and Unusual Populations of the Corresponding 1-(9-Fluorenyl)-2-[(E)-2-halo-1-methylethenyl]naphthalene Rotamers
Authors: Oki Michinori , Hirose Takanori , Maeda Kiyoka , Yanagawa Maki , Kataoka Yasukazu , Kojima Hiroharu , Morita Nobuhiro , Toyota Shinji 
Published: June 2006

Abstract
Reactions of bromine chloride and iodine chloride with the olefinic bond in 1-(9-fluorenyl)-2-(1-methylethenyl)naphthalene rotamers were carried out to examine the product distributions. In the case of the ap-isomer bromine chloride yielded some bromo-olefins in addition to the addition product, whereas the yield of (8R*,14cS*)-8-bromomethyl-8-methyl-8,14c-dihydrodibenzo[a.l]aceanthrylene from the sp-isomer diminished with respect to the case of the reaction between bromine and the sp-isomer. The results are attributed to the low nucleophilicity and high proton affinity of the chloride ion. Iodine chloride afforded more addition product for the ap-isomer than the case of bromine chloride, whereas the sp-isomer reacted with iodine chloride to give a better yield of a cyclized compound, (8R*,14cS*)-8-iodomethyl-8-methyl-8,14c-dihydrodibenzo[a,l]aceanthrylene, than that of the cyclized compound from bromine chloride. Such results are attributed to the better stabilizing effects of an iodo substituent on a β-carbocation than a bromo one. Populations of ap and sp rotamers of 1-(9-fluorenyl)-2-[(E)-2-halo-1-methylethenyl]naphthalenes at equilibrium were unusual in the sense that the ap-isomer of the sterically more crowded iodo compound was favored relative to the less crowded chloro compound. UV absorption spectra were not conclusive for charge transfer interactions but X-ray crystallography of these compounds revealed that the olefinic carbons in the ethenyl group were attracted to the fluorene ring significantly.
Photochemistry of Amino-Linked Bichromophoric Anthracenes. Efficient Cyclomerization of 9-(1-Naphthylmethylaminomethyl)anthracene and Adiabatic Cycloreversion of the Cyclomer
Authors: Mori Yukie , Maeda Koko 
Published: June 2006

Abstract
The spectral and photochemical properties of the title compound 1 and bis(9-anthrylmethyl)amine (2) have been investigated. The fluorescence spectrum of 1 in methylcyclohexane showed an emission from the locally excited state of the anthracene part and a weak broad emission at 410—550 nm from the intramolecular exciplex. The fluorescence quantum yields of 1 and 2 decreased along with an increase in the solvent polarity. Both 1 and 2 underwent intramolecular [4+4] cycloaddition. The quantum yield of the cyclomerization of 1 was 0.24 in acidic methanol, while in MeCN the reaction was completely quenched by an intramolecular electron transfer from the amino group to the excited anthracene moiety. Excitation of the cyclomer from 1 at 285 nm brought about fluorescene from both the locally excited anthracene and the exciplex state, indicating that adiabatic cycloreversion took place on the S1 potential surface. To investigate the conformations, the crystal structures of 1 and 2 were determined and PM3 calculations were performed for 1–H+. The calculations indicate that a conformer in which the two chromophores are located close to each other has a higher energy then other stable conformers.
Methyltrioxorhenium-Catalyzed Oxidation of Secondary and Primary Amines with Hydrogen Peroxide
Authors: Yamazaki Shigekazu 
Published: June 2006

Abstract
The methyltrioxorhenium-catalyzed oxidation of secondary amines and primary amines with hydrogen peroxide has been carried out. The oxidation of secondary amines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C–H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
Relationship between the Cyclization and Conformation of Pentapeptide Active Esters Related to Gramicidin S Having No Protecting Group on the Side Chain of the Ornithine Residue
Authors: Tamaki Makoto , Komiya Seiji , Akabori Sadatoshi , Muramatsu Ichiro 
Published: June 2006

Abstract
To investigate the contribution of the d-Phe–Pro–Val sequence in the direct formation of gramicidin S (GS) by the dimerization–cyclization of pentapeptide-active esters having no protecting group on the side chain of the Orn residue, the cyclization of four H–X–Pro–Y–Orn–Leu–ONSu’s (X = l- or d-Phe, Y = l- or d-Val, –ONSu = succinimide ester) was examined. Only H–d-Phe–Pro–Val–Orn–Leu–ONSu gave semi-GS (cyclic monomer) and GS (cyclic dimer) in yields of 15 and 38%, respectively. The active ester with a d-Phe–Pro–d-Val sequence produced exclusively [d-Val]–semi-GS in 58% yield. On the other hand, the active esters having Phe–Pro–Val and Phe–Pro–d-Val sequences did not yield any amount of cyclic monomer and cyclic dimer. The change in the configurations of the Phe and Val residues around the Pro residue greatly affected the CD spectra in ethanol and the 1H NMR spectra in DMSO-d6 of the pentapeptide ethyl esters corresponding to four H–X–Pro–Y–Orn–Leu–ONSu’s. A good correlation among the CD spectra, NMR spectra of the pentapeptide ethyl esters, and the main products in the cyclization of the active esters was found.
A Halide-Free Method for Olefin Epoxidation with 30% Hydrogen Peroxide
Authors: Sato Kazuhiko , Aoki Masao , Ogawa Masami , Hashimoto Tadashi , Panyella David , Noyori Ryoji 
Published: June 2006

Abstract
A catalytic system consisting of sodium tungstate dihydrate, (aminomethyl)phosphonic acid, and methyltrioctylammonium hydrogensulfate, effects the epoxidation of olefins using 30% hydrogen peroxide with a substrate-to-catalyst molar ratio of 50—500. The reaction proceeds in high yield without solvents, or, alternatively, with added toluene under entirely halide-free conditions. Lipophilic ammonium hydrogensulfate, which replaces the conventional chloride, and an (α-aminoalkyl)phosphonic acid are crucial for the high reactivity. This method is operationally simple, environmentally benign, and much more economical than the oxidation with m-chloroperbenzoic acid, allowing for a large-scale preparation of epoxides. Various substrates including terminal olefins, 1,1- and 1,2-disubstituted olefins, cyclic olefins, and tri- and tetrasubstituted olefins as well as allylic alcohols, esters, α,β-unsaturated ketones, and ethers can be epoxidized in high yield. The scope and limitations of this new reaction system are discussed.
Resonance Effects in the Solvolysis of α-t-Butyl-α-neopentylbenzyl and α-t-Butyl-α-isopropylbenzyl p-Nitrobenzoates
Authors: Fujio Mizue , Ohe Makoto , Nakata Kazuhide , Tsuji Yutaka , Mishima Masaaki , Tsuno Yuho 
Published: June 2006

Abstract
Substituent effects on the solvolysis rates of α-t-butyl-α-neopentylbenzyl and α-t-butyl-α-isopropylbenzyl p-nitrobenzoates in 50% (v/v) aqueous EtOH at 75 °C were correlated with the Yukawa–Tsuno equation to give ρ = −3.37 and r = 0.78, and ρ = −3.09 and r = 0.68, respectively. The reduction in r values from r = 1.00 characteristic of full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. The torsion angles for twisting out of coplanarity were estimated from the relationship r/rmax = cos2 θ for a series of sterically hindered tertiary dialkylbenzylic solvolyses. The torsion angles assigned for these twisted benzylic systems are in good agreement with theoretically calculated dihedral angles of the corresponding 6-31G*optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity, and, in turn, provides strong support for our characterization of the r value as a resonance demand parameter reflecting the degree of resonance (π-delocalization) interaction between an aryl group and the reaction site.
Electron Deficient Porphyrins III. Facile Syntheses of Perfluoroalkylporphyrins Including Water Soluble Porphyrin
Authors: Aoyagi Katsuhiro , Haga Toshihiko , Toi Hiroo , Aoyama Yasuhiro , Mizutani Tadashi , Ogoshi Hisanobu 
Published: June 2006

Abstract
A variety of 3-perfluoroalkyl pyrroles were prepared by reaction of β-perfluoroalkyl α,β-unsaturated carbonyl compounds with p-tolylsulfonylmethyl isocyanide in moderate yields. Tetrakis(perfluoroalkyl)porphyrins were readily obtained by oxidative cyclization of 3-alkyl-2-hydroxymethyl-4-perfluoroalkylpyrroles in acidic media, including water-soluble 3,8,13,18-tetrakis(p-carboxybenzyl)-2,7,12,17-tetrakis(trifluoromethyl)porphyrin. The pKa value for the monoprotonation of its inner nitrogen is less than 1, while that of Copro-I is 7.2. Diprotonation at the inner nitrogen occurs only in concd HCl, while the pKa value of the corresponding non-fluoro porphyrin is 4. The reduction potential of 3,8,13,18-tetrakis(p-methoxycarboxybenzyl)-2,7,12,17-tetrakis(trifluoromethyl)porphyrin was shifted by 580 mV to a less negative value.
Preparations and Reactions of Functionalized Silyllithiums
Authors: Kawachi Atsushi , Tamao Kohei 
Published: June 2006

Abstract
Several types of α-alkoxy and α-amino substituted silyllithiums have been prepared as the first members of stable and/or well-characterizable functionalized silyllithiums. Described herein are new aspects of (1) three methodologies for preparation of functionalized silyllithiums, (2) high stability of (aminosilyl)lithiums, (3) low stability of (monoalkoxysilyl)lithiums, behaving as silylenoid species, (4) high stability of (dialkoxysilyl)lithiums, (5) high stability of (2-alkoxydisilanyl)lithium, (6) first examples of [2,3]-sila-Wittig rearrangement, and (7) synthetic utilization of (aminosilyl)lithiums.
Interfacial Mechanism in the Extraction Kinetics of Ni(II) with 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol and Molecular Dynamics Simulation of Interfacial Reactivity of the Ligand
Authors: Watarai Hitoshi , Gotoh Masashi , Gotoh Narushi 
Published: June 2006

Abstract
Extraction kinetic mechanism of Ni(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was studied by a high-speed stirring spectrophotometry in heptane/water and toluene/water systems. The experimental results revealed that a rate-determining step was the 1 : 1 chelate formation of Ni2+ with 5-Br-PADAP adsorbed at the interface. In situ spectrophotometry of the heptane/water interface proved the formation of Ni(II) complex at the interface. The preferential adsorption of 5-Br-PADAP and its Ni(II) complex in heptane/water interface was correlated with the lower distribution constant in heptane/water than that in toluene/water. Molecular dynamics simulation could reproduce the preferential adsorptivity in heptane/water interface and then the higher reactivity with Ni2+ in the interface. The observed formation rate constants of the Ni(II) complex in bulk aqueous phase and the interfaces were smaller than those expected from the Eigen mechanism. Molecular mechanics calculation supported the ring-closure mechanism, previously postulated as the rate-determining step.
Transformation of Oximes of Phenethyl Ketone Derivatives to Quinolines and Azaspirotrienones Catalyzed by Tetrabutylammonium Perrhenate and Trifluoromethanesulfonic Acid
Authors: Kusama Hiroyuki , Yamashita Yuko , Uchiyama Katsuya , Narasaka Koichi 
Published: June 2006

Abstract
Phenethyl ketone oximes are converted to quinolines by the treatment with tetrabutylammonium perrhenate, trifluoromethanesulfonic acid, and chloranil in refluxing 1,2-dichloroethane. Azaspirotrienones can be synthesized from p-hydroxyphenethyl or 3-(p-hydroxyphenyl)propyl ketone oximes by applying the above method. Thus prepared azaspirotrienones are converted to quinolines by acid treatment.