bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformations of Prolyl Residues in Oligopeptides
Authors: Ashida Tamaichi , Kakudo Masao 
Published: July 2006

Abstract
The structures of the prolyl residues as found in the crystals of various oligopeptides were studied, and a few interesting structural features were found, (i) The Cα–C′–N angle of the peptide group formed by the N atom of the pyrrolidine ring and the Cα and C′ atoms of the preceding residue is widened to about 118° from the usual value of 114° due to the steric repulsion between the Cα and the two hydrogen atoms bonded to the Cδ atom of the pyrrolidine ring, (ii) The Cγ atoms of some pyrrolidine rings have some sort of disorder, and the Cβ–Cγ and Cγ–Cδ bonds seem to be shortened and the Cβ–Cγ–Cδ angles seem to be widened than usual, (iii) Almost half of the pyrrolidine rings have an approximate C2 (half-chair) symmetry, the twofold axis passing through the N atom and the midpoint of the Cβ–Cγ bond. The others have an approximate Cs (envelope) symmetry, the mirror plane passing through either the Cβ or Cγ atom with equal probabilities. In this case the NCαCαCγCδ or NCαCβCδgroups are almost planar, respectively, (iv) The conformation of Cγ-exo against the C′ atom bonded to the Cα atom is mainly found in the residues having the α-helix type torsion angles, while the Cγ-endo is in those having the collagen type torsion angles.
X-Ray Photoelectron Spectroscopy of p-Benzoquinone, Hydroquinone and Their Halogen-Substituted Derivatives
Authors: Ohta Toshiaki , Yamada Masamichi , Kuroda Haruo 
Published: July 2006

Abstract
X-Ray photoelectron spectra of p-benzoquinone, chloranil, bromanil, iodanil, hydroquinone, tetrachlorohydroquinone and chloranilic acid were observed by using the samples freshly deposited in the high vacuum of the spectrometer. The chemical shifts of C ls and O ls levels determined from the XPS spectra are compared with the chemical shifts predicted according to the electrostatic potential model by use of the charge distributions calculated by CNDO/2 method. The charge distributions in the quinone derivatives are successfully estimated by using the observed binding energies of C ls and O ls levels.
Change from Metastable Cubic to Stable Tetragonal Form of Submicron Barium Titanate
Authors: Naka Shigeharu , Nakakita Fumihiko , Suwa Yoshiko , Inagaki Michio 
Published: July 2006

Abstract
The change from metastable cubic to stable tetragonal form was investigated on the submicron BaTiO3 which was prepared by the hydrolysis of titanium tetraisopropoxide in barium hydroxide solution and by crystallization in the glass of BaO–TiO2–SiO2–Al2O3 system. The precipitated BaTiO3 was found to be the aggregates of minute grains of about 100 Å, to have large amount of strain and to absorb about 6% of OH and alcoholic radicals, some of them absorbed chemically. It is in a metastable cubic form. After the heating above 800 °C, it changed to stable tetragonal form in association with weight loss and decrease in lattice strain. The samples heated at 800–900 °C did not show the Curie point on the DTA curve although they were tetragonal. The samples heated at 1300 °C had the Curie point about 122 °C. The glass-devitrified BaTiO3 was also cubic and had large lattice strain. In order to change to tetragonal form, the heating above 1000 °C was needed. The metastable cubic form of submicron BaTiO3 seemed to be stabilized by the absorbants on the surface which balanced with large amount of strain in the lattice.
Photoreactions of Heteroaromatic Compounds. IV. Solvent and Acidity Dependence of the Photoreactions of Nicotinic Acid and Its Derivatives
Authors: Takeuchi Fumikatsu , Sugiyama Tom , Fujimori Takako , Seki Kazuhiko , Harada Yoshiya , Sugimori Akira 
Published: July 2006

Abstract
Nicotinic acid and its derivatives show manifold photoreactivity depending on the solvent and the acidity of the solution. The cationic form of these compounds in general undergoes photo-hydroxylation in aqueous solutions, and photo-ethylation in ethanol solutions. The anionic form of nicotinic acid is resistant to UV-irradiation in strongly alkaline aqueous solution, but undergoes photo-decarboxylation in alkaline ethanol solution. Nicotinic acid yielded 2-(3-pyridyl)-5-pyridinecarboxylic acid in aqueous solutions at pH=4–6. Photo-substitution by 1-hydroxyethyl group occurs in the neutral forms of 3-cyanopyridine and ethyl nicotinate in ethanol solution. The photoreactivity of nicotinic acid is considered on the basis of CNDO/2 calculation.
Mass Spectrometric Study of the Primary Processes in Photochemical Reactions. II. Mass Spectra of Methyl and Ethyl Radicals
Authors: Yamashita Shigeru 
Published: July 2006

Abstract
The mass spectra of methyl and ethyl radicals have been determined by the photolyses of methyl and ethyl iodide using a high intensity light beam and a collision-free photochemical reactor incorporated in the ion-source of a mass spectrometer. The parent ion peak was the most intense in the mass spectra of methyl and of ethyl radicals. Fair agreement was found between the present work and the result obtained by previous workers for pyrolytically produced methyl radicals.
Conditions for the Formation of Fe3O4 by the Air Oxidation of Fe(OH)2 Suspensions.
Authors: Kiyama Masao 
Published: July 2006

Abstract
The optimum conditions were studied for the formation of Fe3O4 by the air oxidation of Fe(OH)2. The suspensions obtained by mixing NaOH and FeSO4 solutions in various values of R(=2NaOH/FeSO4) were subjected to oxidation with air at various temperatures. The oxidation products were then examined by X-ray powder diffraction, chemical analysis, electron microscopic observation, and BET surface-area determination. Fe3O4 is formed at higher temperatures than is FeOOH. The temperature of formation becomes low as R approaches 1.0. In neutral suspensions (R&lt;1), Fe3O4 is formed via green rust II or a mixture of green rust II and Fe(OH)2. By further oxidation, the Fe3O4 formed gradually changes to γ-Fe2O3. A mixture of α-FeOOH and either NaFe3(OH)6(SO4)2 or α-Fe2O3 is formed as the final oxidation product. In alkaline suspensions (R&gt;1), Fe3O4 is formed directly. The morphology and ferrous-ion content of Fe3O4 powder change considerably with the presence of green rust II before the formation of Fe3O4. It is suggested that Fe3O4 is formed near the surface of the particles of Fe(OH)2 and green rust II by the coprecipitation of ferrous ions with ferric hydroxo-complexes.
Binuclear Metal Complexes. IX. Syntheses and Magnetic Properties of Copper(II) and Nickel(II) Complexes of Schiff Bases Derived from 3-Formylsalicylic Acid and Alkyl Amines
Authors: Tanaka Mitsunori , Okawa Hisashi , Tamura Tomoko , Kida Sigeo 
Published: July 2006

Abstract
Copper(II) and nickel(II) complexes of H2fsac-R have been synthesized, where H2fsac-R denotes the Schiff bases prepared from 3-formylsalicylic acid and alkylamines (alkyl(R)=methyl, ethyl, hydroxyethyl, n-propyl, n-butyl, isobutyl, and sec-butyl). On the bases of elemental analyses, IR spectra, visible spectra and cryomagnetic measurements, it was found that the complexes have a binuclear structure connected by two phenolic oxygens; the complexes are abbreviated to M2(fsac-R)2. The nickel(II) complexes contain two, three or four molecules of coordinated water. The cryomagnetic data for Cu2(fsac-R)2 are interpreted in terms of the Bleaney-Bowers equation with large −2 J values (&gt;700 cm−1), indicating the presence of strong intramolecular antiferromagnetic spin-exchange interactions. The Ni2(fsac-R)2·nH2O obey the Curie-Weiss law, the Weiss constants being estimated to −35–−41 K.
The Iodination of Benzene with Iodine in the Thallium(III) Trifluoroacetate-Trifluoroacetic Acid System
Authors: Ishikawa Nobuo , Sekiya Akira 
Published: July 2006

Abstract
Molecular iodine in the system of thallium(III) trifluoroacetate-trifluoroacetic acid has been found to possess a high potency for aromatic iodination. Under controlled conditions, benzene and also mesitylene were stepby-step mono-, di-, and triiodinated, whereupon whole iodine was consumed for the iodination by the oxidation process of the thallium(III) salt. In the course of the iodination of benzene, an intermediate has been revealed to consist of thalliated benzenes, which were transformed into iodinated benzenes by the electrophilic attack of iodine.
Asymmetric Hydroformylation of Styrene. The Effects of the Reaction Conditions on the Stereoselectivity
Authors: Tanaka Masato , Watanabe Yoshihisa , Mitsudo Take-aki , Takegami Yoshinobu 
Published: July 2006

Abstract
The effects of the reaction conditions on the asymmetric hydroformylation of styrene with rhodium catalysts have been studied. The [α]d value and the configuration of the product, hydratropaaldehyde, were much affected by the phosphine/rhodium ratios, the reaction temperatures (20–110 °C), and the partial pressures of carbon monoxide and hydrogen (10–100 atm). The results were mainly explained in terms of the structures of the catalysts and the skeletal isomerization of acyl complexes. The predominant species of the catalysts and the participation of π-benzyl-type intermediate were also discussed.
Formation of Charge-transfer Complexes by Solid State Reaction; Electronic Spectra and Relative Reactivity
Authors: Sato Hiroyasu , Yasuniwa Tamiharu 
Published: July 2006

Abstract
Formation of charge-transfer complexes by solid state reaction was studied for 16 donors and 10 acceptors. The relative reactivity of 160 pairs was determined by the presence or absence of the charge-transfer band on grinding the component pairs of the same concentration (diluted with sodium chloride) for the same length of time. Equilibrium was not reached within the grinding time. This relative reactivity was compared with and found to have a parallel relationship with the relative ease of formation of the charge-transfer complex on evaporating a mixture of the solutions of components, indicating that the relative reactivity is related to an apparent equilibrium established on the grain surface. Relative reactivity was found to be largely dependent on molecular size and geometry. Smaller molecules were more reactive. For molecules with the same number of rings, those with compact structure were more reactive. Most of the new bands given by the reaction were CT bands of microcrystals. They were very broad. A fairly good linear relationship was found between the transition energies of the CT bands and the ionization potentials of the donors or the electron affinities of the acceptors.
The Crystal and Molecular Structure of Tris(π-cyclopentadienyl nickel) tertiary-butylammonium
Authors: Kamijyo Nagao , Watanabé Tokunosuké 
Published: July 2006

Abstract
The crystal structure of tris(π-cyclopentadienylnickel)tertiary-butylammonium, t-C4H9N(π-C5H5Ni)3, has been determined from single crystal X-ray diffractometer data. The space group is C2/c and the lattice constants are a=28.40 Å, b=9.16 Å, c=15.28 Å, β=100°30′, and Z=8. The refinement was carried out using block-diagonal least-squares calculation including anisotropic temperature factors for the three nickel atoms. The final R index for 1620 reflections is 0.138. The molecule is of approximately a trigonal pyramidal structure with an apical nitrogen atom on a triangle of the nickel atoms. The interatomic distances are 2.33–2.39 Å for nickel to nickel, 1.93–1.98 Å for nickel to nitrogen. The distances between a nickel atom and a centroid of a cyclopentadienyl ring are 1.74–1.81 Å. The three cyclopentadienyl rings are inclined to the nickel triangle plane at 68°–69°.
Effect of pH on the Circular Dichroism(CD)-sensitive Transitions of Some Lanthanoid(III) Complexes and “Pseudo CD-sensitive Transitions” of Europium(III) and Terbium(III) Complexes
Authors: Misumi Seizo , Isobe Toshiyuki , Furuta Haruko 
Published: July 2006

Abstract
The effect of pH on the CD-sensitive transitions of lanthanoid(III) complexes with l-propylenediaminetetraacetic acid(l-PDTA) and l-ethylenediaminedisuccinic acid(l-EDDS) was studied. The relation between the cross-over pH where the CD pattern changes or sign of CD reverses and the number of 4f-electrons in lanthanoid(III) complexes with l-EDDS showed a tetrad curve. A strong evidence for coordination of hydroxide ions was suggested. “Pseudo CD-sensitive bands” in the spectra of the complexes of europium(III) and terbium(III) which do not obey the selection rule ΔJ≤1 were found, and the mechanisms of these transitions were elucidated.
SORPTION OF VAPOUR BY CHABAZITE
Authors: Baba Tositomo 
Published: July 2006

Abstract
1. The sorption amounts and velocities by chabazite of fifteen substances have been measured at 25.0°C. by a statical method.
2. The sorption amounts of the vapours of pentane, benzene, ether, chloroform, carbon tetrachloride, acetone, and ethyl acetate have been found to be negligibly small, while those of methyl alcohol, methyl amine, carbon dioxide and carbon bisulphide have been found to be great. Ethyl alcohol, ethyl amine, propyl amine and butyl amine have been slightly sorbed.
3. No change in appearance of the mineral has been observed by the first sorption of alcohols, amines and carbon dioxide, but in the case of carbon bisulphide the crystal of chabazite have becomes yellow in colour, probably indicating catalytic decomposition of this vapour into free sulphur, hydrogen sulphide and other decomposition products.
4. By the repeated sorptioas of methyl amine, methyl alcohol and ethyl alcohol, the crystals of chabazite have become more or less fragile, and by heating and evacuating these fragile crystals have disintegrated themselves into fine powders.
5. The vapours which have large molecular volumes are generally difficult, if not impossible, to be sorbed by chabazite. The large gaps in sorption amounts between methyl and ethyl compounds in alcohol and amine series may be attributed to the same reason.
6. With regard to the sorption velocities of alcohols, the following formula has been applied which has some theoretical meaning:
(Remark: Graphics omitted.)
where x is the sorption amount at time t, and a, b, k and h the empirical constants.
ATOMIC HYDROGEN OCCLUDED IN IRON NITRIDE
Authors: Satoh Shun-ichi 
Published: July 2006

Abstract
The author confirms the existence of atomic hydrogen in iron nitride:
(1) By the presence of hydrogen when heating iron nitride above 430°C. at which iron nitride is found to decompose slowly.
(2) By the measurement of the single potential of iron nitride in the normal ferrous sulphate solution.
(3) By the oxidation of atomic hydrogen due to oxygen in the water in which iron nitride is immersed.
(4) By the transformation of potassium ferricyanide into potassium ferrocyanide by atomic hydrogen occluded in iron nitride.
By measuring the single potential of nitrided iron, he observed the change of compact iron into porous iron by nitriding.
The influence of light on the single potential of iron nitride was tested and it was found that light produces no marked photo-chemical effect upon it.
Spectroscopic and Equilibrium Dialysis Studies of the Poly(acrylic acid)–Cu(II) Complex in the pH Range 3.5–7
Authors: Yamaoka Kiwamu , Masujima Tsutomu 
Published: July 2006

Abstract
The complex formation between poly(acrylic acid), poly(Acr), and Cu2+ ion was studied in 150 mM NaCl solutions at 25 °C and at the mixing ratios of Acr residues-to-Cu2+, R, of 32, 16 and 8, in the pH range of 3.5–7 by the spectroscopic and equilibrium dialysis methods. The dialysis results showed that more than 90% of the Cu2+ ions remain bound to the polymer at pH’s higher than 4.5, but the bound Cu(II) begins to dissociate at lower pH values. The data also revealed that the true absorption spectra of poly (Acr)–Cu(II) complexes varied with pH and R in a complicated manner. The analysis of the bound Cu(II) spectra disclosed the presence of three different kinds of Cu(II)–Acr complexes over the entire pH range. It is the relative amounts of these three complexes that vary with pH and R. With a newly devised plot of the dialysis data, the stability constant for each Cu(II)–Acr complex was determined. In the poly(Acr)–Cu(II) macrocomplex, each Cu(II) was estimated to bind to two or four carboxylato ligands.
Oxidation-reduction Equilibrium between Anion Radicals. Electron-accepting Property of 2,3-Dichloro-5,6-dicyano-p-benzoquinone
Authors: Iida Yôichi 
Published: July 2006

Abstract
The electron affinity and the oxidation-reduction potential of 2,3-dichloro-5,6-dicyano-p-benzoquinone were estimated by means of the equilibrium constant of the preferred electron transfer reaction between anion radicals in acetonitrile solution.
Nucleophilic Ion Pairs. 6. Catalytic Hydrolysis of p-Nitrophenyl Acetate by Zwitterionic Hydroxamate Nucleophiles in Representative Micellar Systems
Authors: Kunitake Toyoki , Okahata Yoshio , Tanamachi Shoichi , Ando Reiko 
Published: July 2006

Abstract
Several surfactant-like zwitterionic hydroxamates were synthesized and their reactions with p-nitrophenyl acetate were studied in water in comparison with those of simple, anionic hydroxamates. The zwitterionic hydroxamates showed enhanced reactivities in cationic, zwitterionic and nonionic micelles: 20–100 times relative to the nomicellar rate at pH 8.9, 30 °C. The rate enhancement was attributed to lowered pKa values and to activation of the hydroxamate anion in the hydrophobic domain. The rate was suppressed in an anionic micelle because of the enhanced pKa value. Deacylation of the acetyl hydroxamate intermediate was hydroxide-catalyzed. The enhanced reactivity of the zwitterionic hydroxamate in organic media was less sensitive to the water concentration than that of the hydroxamate ion pair. These results can be explained in terms of “hydrophobic ion pair.”
A Rapid Esterification by Means of Mixed Anhydride and Its Application to Large-ring Lactonization
Authors: Inanaga Junji , Hirata Kuniko , Saeki Hiroko , Katsuki Tsutomu , Yamaguchi Masaru 
Published: July 2006

Abstract
A rapid and mild esterification method using carboxylic 2,4,6-trichlorobenzoic anhydrides in the presence of 4-dimethylaminopyridine was developed. The method was also successfully applied to the synthesis of large-ring lactones, including Dl-2,4,6-tridemethyl-3-deoxymethynolide.
Both Oxidation and Reduction of Aromatic Hydrocarbons by an Electrolysis Cell Designed for Low-temperature ESR Studies
Authors: Ohya-Nishiguchi Hiroaki 
Published: July 2006

Abstract
A simple two-electrode cell for low-temperature electron spin resonance (ESR) measurements has been designed. A helical gold wire, the working electrode with large surface area (12 cm2), generated intra muros enough positive or negative ions to measure the ESR spectra of unstable radical ions at low temperatures. To test the electrolysis conditions of the cell, the ESR spectra of about 20 aromatic compounds have been observed at temperatures as low as −90 °C. It has been shown that the cell can be applicable to the compounds with half-wave potential of 1.5 to −3.7 V SCE, provided that the ions produced are not reactive. The experimental conditions of the dimer cation generation have also been checked in polar or nonpolar solvents.
An Alternative Method of Solving the Rose-Drago Equation for the Determination of Equilibrium Constants of Molecular Complexes
Authors: Seal Bejoy K , Mukherjee Ashok K , Mukherjee Dulal C 
Published: July 2006

Abstract
An alternative method for solving the Rose-Drago equation for the determination of equilibrium constants of molecular complexes has been developed. It yields well-defined K values even for certain systems in which the Rose-Drago procedure for solving the R-D equation is not satisfactory. Our method is based on the transformation of the Rose-Drago equation into one involving three variables and using two linear plots. In applying the method to a wide variety of experimental data, the calculated values of the equilibrium constant have been found to be in excellent agreement with those computed by the well-known iterative procedure. With good data, the calculated values are in good agreement with those from the Benesi-Hildebrand or some other modified plots.
Pre-exponential Factor in Semiconducting Vitamin A (Alcohol and Acetate)
Authors: Mallik Biswanath , Ghosh Alpana , Misra T N 
Published: July 2006

Abstract
The semiconductive properties of vitamin A (alcohol and acetate) on adsorption of various vapors have been studied. The adsorbed vapors increase the semiconduction currents by several orders of magnitude and decrease the semiconduction activation energies. Such change depends on the chemical nature and also on the amount of vapor adsorbed. Semiconducting vitamin A follows the three-constant equation
σ(T)=σ0′exp(E⁄2kT0)exp(−E⁄2kT)
where the conventional pre-exponential factor σ0 has been replaced by σ0′exp(E⁄2kTo) (the so called compensation effect). Here T0 and σo′ are constants for the substance and T0 is called the characteristic temperature. Various methods used for evaluating these constants have yielded consistent results with T0≈402 K and σ0′≈2.8×10−9 Ω−1 cm−1 for vitamin A alcohol and T0≈335 K and σ0′1.5×10−10 Ω−1 cm−1 for vitamin A acetate. Excellent correlation obtained between the relevant parameters in semiconducting vitamin A indicates that σ0 and E are physically related. Various models for conduction mechanism leading to compensation effect have been discussed. The measured activation energies on adsorption of same amount of various vapors show a linear relationship with the ionization potential of the adsorbed molecules suggesting that charge-transfer interaction is responsible for the semiconductivity enhancement.
Scalar Coupling and Spin-rotation Interactions in the 13C Nuclear Magnetic Relaxation of Methyl-d3 Bromide
Authors: Yanagisawa Masaru , Yamamoto Osamu 
Published: July 2006

Abstract
13C NMR relaxation times have been obtained for methyl-d3 bromide at room temperature, from which the spin-spin coupling constant between 13C and 79Br has been extracted and found to be 41.6±2.0 Hz. The contribution of the spin-rotation interaction to the 13C relaxation is large in this molecule. This fact may be attributed to the presence of a methyl rotor, but cannot be satisfactorily interpreted in the framework of the present theories.
A Hydroxyl Proton Magnetic Resonance Study of 2-Cyclohexen-1-ols, 1-Tetralols, 4-Chromanols, and 4-Thiochromanols in Dimethyl Sulfoxide
Authors: Hanaya Kaoru , Kud\={o} Hideaki , Gohke Kazuo , Imaizumi Shin 
Published: July 2006

Abstract
The proton magnetic spectra in dimethyl sulfoxide of 2-cyclohexen-1-ols, 1-tetralols, 4-chromanols, and 4-thiochromanols have been determined. In all cases, the pseudoaxial OH proton resonates at a higher field than the pseudoequatorial one. The spin-spin coupling between the hydroxyl and carbinyl protons is found to be greater for the pseudoequatorial epimer.
A Comparative Study of Nickel and Cobalt Catalysts in the Hydrogenation of Substituted Acetophenones. Dependence of Hydrogenation Rate and Adsorption Strength on Substituents and Solvents
Authors: Kajitani Masatsugu , Suzuki Naoki , Abe Tsutomu , Kaneko Yoshimitsu , Kasuya Kazuhiko , Takahashi Kazunori , Sugimori Akira 
Published: July 2006

Abstract
The difference in the nature of nickel and cobalt catalysts has been investigated by a comparative study of the competitive hydrogenation of substituted acetophenones. The electronic and steric effects of substituents and the effects of solvents on the adsorption strength of acetophenones are greater for the reactions over R-Ni than for those over R-Co. On R-Co catalyst acetophenones substituted with electron attracting groups (3-methoxyl, 3-hydroxyl, and 4-fluoro groups with σ0&gt;0) are adsorbed more strongly than those with electron donating groups (2-, 3-, and 4-alkyl and 4-methoxyl groups with σ0&lt;0). Over R-Ni catalyst the adsorption of acetophenone is greater than that of any substituted acetophenones. The rates of hydrogenation over R-Ni are more susceptible to the effects of substituent and solvent than those over R-Co. Over both R-Ni and R-Co the rates of hydrogenation of unsubstituted acetophenones are greater than those of substituted acetophenones with either electron donating or electron attracting groups.