bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass Spectrometric Studies of Some Carboxylic Acid Dimers Produced by a Nozzle Beam: HCO2H, CH3CO2H, C2H5CO2H, and n-C3H7CO2H
Authors: Mori Yoshihiro , Kitagawa Taiji , Yamamoto Tomoki , Yanada Kazuo , Nagahara Shigeru 
Published: July 2006

Abstract
Characteristic ions (M+1)+ and (M+45)+, assigned to be the protonated monomer ion MH+ and (M·CO2H)+ respectively, have been detected in the mass spectrometric measurements of the dimer molecules M2 and the higher clusters Mn of some carboxylic acids produced in their nozzle beams. It has been shown from the dependences of their relative intensities on the stagnation conditions that these ions are mainly formed through the fragmentation of the dimer ions. The MH+ ion plays the most important role in these fragmentation processes of the dimers, while no dimer ion M2+ was observed. These results are discussed in terms of the enthalpy changes for the unimolecular decomposition reactions of M2+.
Electron Spin Resonance Study of Cu(II)–Crown Ether Complexes with 3dZ2 Ground State Doublet in Solution
Authors: Ishizu Kazuhiko , Haruta Tokuhiro , Kohno Yuji , Mukai Kazuo , Miyoshi Kiyonori , Sugiura Yukio 
Published: July 2006

Abstract
Copper(II) chloride and crown ethers (12-crown-4, 15-crown-5 and 18-crown-6) formed orange or orangeyellow complexes in dry chloroform. We found that the ESR g-anisotropy of the complexes was greatly dependent on the numbers of donor oxygens and the ring-numbers. The complexes obtained from 12-crown-4 and 18-crown-6 showed g-anisotropy (g⁄⁄&gt;g⊥); these are well characterized by the 3dx2−y2, or 3dxy ground state. On the other hand, the complexes of 15-crown-5 and its benzo derivatives exhibited the reverse g-anisotropy (g⁄⁄&lt;g⊥); these are characterized by the 3dz2 ground state with S=1/2. The electron nuclear dipolar term and the Fermi’s isotropic term were estimated from the ESR parameters based on Bleaney’s calculation. The chlorine superhyperfine splittings were observed in the g⁄⁄- component. The MO bonding parameters were estimated by assuming the compressed octahedral, the trigonal bipyramidal, and pentagonal bipyramidal geometry at the paramagnetic site. The bonding nature was studied on the basis of the observed ligand spin densities.
The trans-cis Isomerization of the Diaquabis(malonato)chromate(III) Ion in Various Organic Solvent–Water Mixtures
Authors: Uchida Kengo , Takinami Yoshinobu 
Published: July 2006

Abstract
The kinetics of the trans-cis isomerization of [Cr(mal)2(H2O)2]− have been investigated in binary mixed solvents, including methanol-, ethanol-, dioxane-, and acetone-water mixtures. The first-order rate constant increases with a decrease in the volume percentage of the water, but is independent of the kind of organic solvent. The rate is not affected by the addition of any cation to an aqueous solution. These results are in contrast to those for the analogous oxalato complex, and are interpreted in terms of a dissociation mechanism in which the rate-determining step is the dissociation of the coordinating water molecule.
The Stereochemistry and Reactivity of Metal-Schiff Base Complexes. III. The Kinetic and Thermodynamic Stereoselectivities in the Formation of N,N′-Ethylenebis(α-methylsalicylideneaminato)cobalt(III)Complexes with l-Proline, Hydroxy-l-proline, and allo-Hydroxy-l-proline
Authors: Fujii Yuki , Shiono Katsuji , Ezuka Kuniko , Isago Takashi 
Published: July 2006

Abstract
Under air-oxidation conditions, the reaction of [Co(α-Me-sal2en)] with l-aaH, where α-Me-sal2en represents the dianion of N,N′-ethylenebis(α-niethylsalicylideneaniine) and where l-aaH denotes l-proline, hydroxy-l-proline, or allo-hydroxy-l-proline, proceeded rapidly to yield Λ-cis-β2–[Co(α-Me-sal2en)(l-aa)] stereoselectively, followed by the slow isomerization of the Λ-cis-β2-isomer thus formed to give the corresponding Δ-cis-β2-isomer in a yield of almost 100% under equilibrium conditions. The complexes thus formed were isolated and characterized by the use of their absorption, circular dichroism, and 1H-NMR spectra. The preferential formation of the Λ-cis-β2-isomer in the initial reaction was found to be kinetic in origin. The kinetic stereoselectivity was determined to be 87% for l-proline, 56% for hydroxy-l-proline, and 23% for allo-hydroxy-l-proline by the measurement of the rotation at 435 nm of the reaction solutions. On the other hand, no kinetic differentiation was observed for the formation of the similar cis-β2-complexes with l-alanine, l-valine, l-methionine, l-phenylalanine, l-tryptophan, N-benzyl-l-alanine, and N-methyl-l-alanine. On the basis of these data, the mechanism of the initial complexation was discussed. The high thermodynamic stereoselectivity for Δ-cis-β2-isomer was explained in terms of the intramolecular steric interaction between the pyrrolidine ring of the coordinated l-aa and the distorted α-Me-sal2en ligand in the complex.
Configurations of Solvated Complex Ions of First Transition Metals in Hexamethylphosphoric Triamide as Inferred from Their Absorption Spectra and Stokes Radii
Authors: Abe Yuriko , Wada Goro 
Published: July 2006

Abstract
The absorption spectra and Stokes radii of solvated complex ions of first transition metals (Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)) were observed in hexamethylphosphoric triamide (HMPA) in order to determine their configurations. It seems that the Stokes radii of complex ions are sensitive to the configurational change, since the diameter of an HMPA molecule is very large as compared with the crystallographic diameters of central metal ions. As to the result, metal ions are tetrahedrally solvated in the cases of Mn(II), Fe(II), Co(II), and Cu(II), while in the case of Ni(II), equilibria are established among octahedral, square planar and tetrahedral solvated species. Zn(II) forms probably a complex ion solvated octahedrally by HMPA.
Anodic Stripping Semidifferential Electroanalysis of Mercury(II) at Gold Disk Electrode and Its Application to Environmental Analysis
Authors: Goto Masashi , Ikenoya Kazuhiko , Ishii Daido 
Published: July 2006

Abstract
Anodic stripping semidifferential electroanalysis using a gold disk working electrode was proposed for the trace determination of mercury(II) ion, theoretical predictions being verified. A gold electrode was steeped in aqua regia, activated electrochemically before use, and rotated during the course of pre-electrolysis. A hydroxylamine hydrochloride medium was selected as supporting electrolyte. The detection limit was found to be ca. 0.5 nM under the pre-electrolysis conditions of 10 min at 0 V vs. Ag/AgCl. The relative standard deviation was ca. ±4% for the measurement at 2 nM level. Removal of the oxygen dissolved in sample solutions was not necessary. Experiments were carried out to examine the feasibility of the technique to environmental analysis. The method consists of only the following procedure: sample acidification, standard mercury(II) ion addition, UV irradiation pretreatment, and medium exchange for stripping. It was successfully applied to river water and sea water to separately evaluate ionic mercury, mercury occluded in organic matter, and total mercury (excluding mercury occluded in inorganic matter).
The Reduction of Hexakis(urea)chromium(III) Ions at the Dropping Mercury Electrodes
Authors: Yamada Akifumi , Nakabayashi Yasuo , Yoshikuni Tadatsugu , Tanaka Nobuyuki 
Published: July 2006

Abstract
The polarographic reduction of hexakis(urea) chromium (III) ions at the dropping mercury electrode has been studied in various supporting electrolyte solutions. This complex exhibits two irreversible reduction waves; the first corresponds to Cr(III)→Cr(II), and the second, to Cr(II)→Cr(0). The kinetic parameters of the electrode reactions were determined in various supporting electrolyte solutions and at varied ionic strengths by means of Tast polarography. The differential-pulse polarographic characteristics of this complex are also given.
Preparation and Characterization of Dinuclear Cobalt(III) Complexes Bridged by Quadridentate Ligand with Thioether Donor Atoms
Authors: Yamanari Kazuaki , Shimura Yoichi 
Published: July 2006

Abstract
From the reaction of (2-aminoethanethiolato)bis(ethylenediamine)cobalt(III)(2+) complex with α,ω-dibromoalkanes Br(CH2)nBr, a series of novel monobridged dinuclear cobalt(III) complexes [(en)2Co{NH2(CH2)2S(CH2)nS(CH2)2NH2}Co(en)2]6+ (n=1, 2, 3, 4, 5, 6, 8, and 10) were prepared and characterized on the basis of their absorption, circular dichroism, and infrared spectra and elemental analyses. In the case of n=2, two geometrical isomers, meso and rac, were isolated and identified.
Neighboring Group Participation in the Oxidation of Hydroxy Sulfides. Control of the Reaction Courses and Products
Authors: Ueno Yoshio , Miyano Tadaaki , Okawara Makoto 
Published: July 2006

Abstract
Oxidation of the hydroxy sulfides [PhS(CH2)nCH(OH)R] with hexabutyldistannoxane (HBD)–bromine system was studied in order to clarify neighboring group participation during the course of reaction. The oxidation products were found to be highly dependent on the positions of the two functional groups [sulfide and hydroxyl group]. Thus hydroxy sulfoxides [PhSO(CH2)nCH(OH)R] were obtained as the main product when n=1 or 2, bromo sulfones [PhSO2(CH2)nCHBrR] being predominant when n=3 or 4. Keto sulfoxide [PhSO(CH2)nCOR] was exclusively formed when n=6. The results are discussed in terms of the different intramolecular interactions depending on the positions of the two functional groups.
The Conformations of Several Aliphatic Alcohols. The General Occurrence of the Attractive Alkyl/Phenyl Interaction
Authors: Uzawa Jun , Zushi Shoji , Kodama Yoshio , Fukuda Yoshimasa , Nishihata Ken , Umemura Koshiro , Nishio Motohiro , Hirota Minoru 
Published: July 2006

Abstract
The conformation has been studied, by means of NMR spectroscopy, for diastereoisomeric pairs of a series of alcohols having the following general structure:
CH_3CH(C_6H_5)CH(OH)–R
where R is a methyl, ethyl, isopropyl, or a t-butyl group. It has been demonstrated that the alkyl group (R) is oriented close to the phenyl group in the most preferred conformations; this conclusion is essentially in accord with the results obtained for the structurally related sulfoxides. The general occurrence of an attractive interaction (the CH/π interaction) has, therefore, been suggested between an alkyl and a phenyl group.
Modification of Aminocyclitol Antibiotics. 8. Preparation of 5,6″-Dideoxykanamycin B
Authors: Suami Tetsuo , Nakamura Katsumi 
Published: July 2006

Abstract
In order to obtain an effective antibiotic against a resistant strain of bacteria, two hydroxyl groups on C-5 and 6″ of kanamycin B were removed. 5,6″-Dideoxykanamycin B thus prepared was subjected to antimicrobial tests, its structure being established by mass and 13C NMR spectroscopy.
Nucleophilic Substitution on Dialkoxy Disulfides. III. Reaction with Thioureas
Authors: Kagami Hiroaki , Hanzawa Takashi , Suzuki Nobuo , Yamaguchi Shoso , Saito Masami , Motoki Shinichi 
Published: July 2006

Abstract
1,3- and 1,1-Disubstituted thioureas reacted with diethoxy disulfide to give carbodiimides and 1,2,4-thiadiazoles respectively. 1,1,3-Trisubstituted thioureas and diethoxy disulfide afforded trialkyl(trialkylamidino)thioureas.
Studies of Unusual Amino Acids and Their Peptides. XIII. The Chemistry of N-(Carboxy methyl) amino Acids. II. The Synthesis of Peptides Containing N-(Carboxymethyl) amino Acids
Authors: Miyazawa Toshifumi 
Published: July 2006

Abstract
The basic problems in the synthesis of peptides with N-carboxymethyl(Cm-)amino acids were investigated. Several kinds of N-protected derivatives of a free Cm-amino acid and the N-benzyloxycarbonyl (Z) derivative of its monoester were obtained by the conventional methods used for the parent amino acid. The peptide-bond formation at either carboxyl group of a Cm-amino acid proved to be achievable by the usual methods, such as the carbodiimide, dicyclohexylcarbodiimide–1-hydroxybenzotriazole, or mixed anhydride method, as illustrated by the examples using the Z–Cm-amino acid derivatives as the carboxyl components. On the other hand, a peptide using a Cm-amino acid diester as the amino component could not be prepared by the usual methods mentioned above. The desired compound was eventually obtained by the acid chloride method. A peptide containing a Cm-amino acid with the free imino group was also prepared by the condensation of a bromoacetylated amino acid ester with an amino acid or peptide ester.
The in Situ-generated Nickel(0)-catalyzed Reaction of Aryl Halides with Potassium Iodide and Zinc Powder
Authors: Takagi Kentaro , Hayama Naomi , Inokawa Saburo 
Published: July 2006

Abstract
The in situ-generated nickel(0) species, presumably atomic nickel, from nickel(II) salt and zinc powder has been proved to be an effective catalyst for the Finkelstein-type displacement reaction of aryl bromides with potassium iodide to give aryl iodides under mild conditions. This species was also effective for the Ullmann-type coupling of bromides or aryl iodides by the use of zinc powder to give biaryls. Furthermore, in the presence of excess nickel(II) salt, the coupling reaction proceeded smoothly, even at an ambient temperature, to give various biaryls in very good yields.
Synthesis of 2-Formylazulene and Its Derivatives by Oxidative Cleavage of 2-Styrylazulenes
Authors: Saito Motoyasu , Morita Tadayoshi , Takase Kahei 
Published: July 2006

Abstract
2-Formylazulene and its derivatives were prepared by the oxidative cleavage of styrylazulenes with NaIO4−OsO4. 1,2-Diformyl-, 1,2,3-triformylazulenes, and 5-formylazulene derivative were also synthesized. The reaction of dimethyl 2-methylazulene-1,3-dicarboxylate with p-nitroso-N,N-dimethylaniline in the presence of NaOR (R=Me or Et) gave the corresponding 3-alkoxycarbonyl-2-[p-(dimethylamino)phenyliminomethyl]azulene-1-carboxylic acids followed by hydrolysis with hydrochloric acid to give 3-alkoxycarbonyl-2-formylazulene-1-carboxylic acids. Acetylation of 2-formylazulene-1-carboxylic acids with acetic anhydride gave five membered lactol acetates.
The Effect of Fatty Alcohols on the Dodecane–Water and the Dodecane–SDS Solution Interfaces
Authors: Mieno Fumitake , Ogino Keizo 
Published: July 2006

Abstract
The effects of fatty alcohols (CmH2m+1OH, m=1–12) at the dodecane–water and the dodecane–sodium dodecyl sulfate (SDS)-solution interfaces has been investigated by measuring the interfacial tension and by observing the stability of the emulsion. The following results have been obtained: the addition of lower alcohols (m=1–3) increases the interfacial tenrion at the dodecane–SDS-solution interface, and they are considered as emulsion breakers. With regard to middle and higher alcohols, though, the interfacial tension decreases with the increase in the carbon number. They can thus be used as emulsion stabilizers.
Energy Transfer in γ-Irradiated Cyclohexane–Benzene Mixture Studied by Spin Trapping-ESR Technique
Authors: Doba Takahisa , Nishimura Susumu , Ichikawa Tsuneki , Noda Shoji , Yoshida Hiroshi 
Published: July 2006

Abstract
Cyclohexyl and phenyl radicals were detected in γ-irradiated cyclohexane-benzene mixtures by a spin trapping-ESR technique. The dependence of the radical yields upon mixture composition showed that energy transfer occurs efficiently from cyclohexane to benzene with the transfer efficiency of ca. 0.5 dm3 mol−1.
Optical Resolution of (2-Aminoethyl)butylphenylphosphine and the Absolute Configuration Assigned on the Basis of Circular Dichroism Spectra of Its Palladium(II) Complexes
Authors: Kinoshita Isamu , Kashiwabara Kazuo , Fujita Junnosuke 
Published: July 2006

Abstract
(2-Aminoethyl)butylphenylphosphine was resolved with (+)D-di-μ-chlorobis[(S)-N,N-dimethyl-α-methylbenzylamine-2C,N]dipalladium(II), and the absolute configuration of the chiral phosphorus atom was assigned on the basis of the circular dichroism spectra of dichloro palladium(II) complexes with the resolved aminophosphine.
Application of the MTPA Method to Determination of Abusolute Stereochemistry. The Hydroxymethyl-substituted Chiral Carbon of Carbocycles
Authors: Sugimoto Yayoi , Tsuyuki Takahiko , Moriyama Yoshihiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
Application of the MTPA method is extended to determination of the absolute configuration of primary alcohols such as furanoeremophilan-14-ol and 17β-(hydroxymethyl)androst-5-ene with a hydroxymethyl group on the chiral ring carbon atom of carbocycles.
Amine Base-catalyzed H-D Exchange Reaction of 2,3,4-Trimethyl-thiazolium Iodide in Methanol-d4
Authors: Yano Yumihiko , Tamura Yoshiharu , Tagaki Waichiro 
Published: July 2006

Abstract
The rates of amine base-catalyzed H-D exchange of 2-methyl hydrogens of 2,3,4-trimethylthiazolium iodide were measured in deuterated methanol by using following amines: α-picoline, imidazole, 2- and 4-aminopyridine. The results indicated that the reaction was subject to a general base catalysis. The solvent effect is also described.
Adsorption of Orthophosphate on a Synthetic Silica–Alumina
Authors: Tokunaga Shuzo , Shiokawa Jiro 
Published: July 2006

Abstract
The characteristics and mechanism of the adsorption of orthophosphate on a commercial synthetic silica–alumina, Neobead D, were studied. The adsorption rate increased with decrease in pH and increase in the dose of silica–alumina below the concentration of 4 g dm−3. The adsorption almost terminated in 24 h, but a very slow reaction was observed even after 3 d. The adsorption isotherm follows the Freundlich equation, the inflection in the log-log plot indicating difference in the adsorption mechanism between low and high phosphate concentrations. The adsorption capacity increased with decrease in pH, being the highest at an initial pH of 3.0. The silica–alumina exhibited buffer action, phosphate-free solutions of pH 4–10 showing pH of ca. 6 after 24 h. In coincidence with and in proportion to the adsorption, release of hydroxide, sulfate and silicate ions occurred in the reaction of initial pH of 4.7. The sum of the equivalents of the three anions released could well account for the moles of phosphate adsorbed. The adsorption thus proceeds mainly through the ion-exchange process between phosphate in solution and the anions on the solid, univalent phosphate ions taking part in the reaction.
Lifetimes of ortho-Positronium in Benzene Solutions of β-Diketonates of Iron(III) and Cobalt(III)
Authors: Endo Kazutoyo , Furukawa Michiaki , Yamatera Hideo , Sano Hirotoshi 
Published: July 2006

Abstract
The lifetimes of ortho-positronium (o-Ps) have been measured in benzene solutions of β-diketonates of iron(III) and cobalt(III). A trend in substituent effect on the acceleration of o-Ps decay has been found. A substituent such as trifluoromethyl, that tends to withdraw electrons from the chelate ring, greatly accelerated o-Ps decay; the greatest rate constant observed was 33.8×109 M−1 s−1 for tris(hexafluoroacetylacetonato)iron(III). An electron-releasing substituent such as t-butyl accelerated o-Ps decay to a lesser extent, e.g. 10.5×109 M−1 s−1for tris(dipivaloylmethanato)iron(III). The extent to which a complex accelerated o-Ps decay was largely related to the redox potential, which was observed by cyclic voltammetry. Complexes with phenyl substituents in the ligand showed slightly smaller effects than that suggested by their redox potentials.
Picosecond Spectroscopy Studies of the Intersystem Crossing of Aromatic Carbonyl and Nitro Compounds in Solution
Authors: Ohtani Hiroyuki , Kobayashi Takayoshi , Suzuki Kaoru , Nagakura Saburo 
Published: July 2006

Abstract
The build-up time constants of Tn←T1 transition bands were measured with 4-hydroxybenzophenone, Michler’s ketone, 2-nitrofluorene, 1-nitropyrene, and 9-nitroanthracene in solution with the aid of picosecond spectroscopy. All the compounds exhibit fast build-up of the Tn←T1 absorption with the time constants smaller than 100 ps. The picosecond kinetics of these nonfluorescent compounds are interpreted in terms of the electronic structures of initial and final states relevant to radiationless transitions.
Ab Initio Calculation of Force Constants of Hydroxylamine
Authors: Hamada Yoshiaki , Tsuboi Masamichi , Umeyama Hideaki 
Published: July 2006

Abstract
Ab initio molecular orbital calculation has been applied to hydroxylamine molecule to reach a reliable set of force constants by the use of the 4-31G basis set. This approach was found to be an enlightening way to solve a problem of the so far undeterminable amino twisting frequency. For this, the value of 1250±100 cm−1 was estimated. A few comments are also given on the theoretical and experimental values of force constants.
Hydration Numbers of Sodium Chloride in Dioxane–Water Mixtures and the Volume Change Accompanying Hydration
Authors: Okuwa Tsunemichi 
Published: July 2006

Abstract
The density and the ultrasonic velocity were measured for dioxane–water solutions of sodium chloride at 25 °C. The hydration numbers of sodium chloride were estimated and were compared with those determined by electricalconductivity measurements. The difference between them was discussed. The volume change caused by the dissociation of sodium chloride in a 60 wt % aqueous dioxane solution was determined from the data of the apparent molal volume. This value is in good agreement with that calculated from the excess ultrasonic absorption.
Polar Fluorescent State of 1- and 2-Acylanthracenes. II. The Perturbation of Protic Solvents
Authors: Tamaki Takashi 
Published: July 2006

Abstract
The steady-state and time-resolved fluorescence spectra were measured for protic solutions of 1- and 2-acetyl- or 1- and 2-benzoylanthracenes at various temperatures. It has been demonstrated that the perturbation of protic solvents on the fluorescence spectra is caused by a combination of the orientational dipolar solvent-solute relaxation and the hydrogen bond interaction. Based on the time-dependent spectral shift and the temperature dependence of fluorescence polarization observed for 2-acylanthracene, the relaxation process of the excited solute has been supposed to involve the level inversion of dual fluorescent states, which respond differently to the solvation of the system.
Complex Formation and Ionization in 3,5-Dialkyl-4-hydroxybenzylidenemalononitrile in the Ground State, and Non-radiative Relaxation in the Excited State
Authors: Mizukoshi Hiroko , Itoh Michiya 
Published: July 2006

Abstract
The interaction of 3,5-dialkyl-4-hydroxybenzylidenemalononitrile (HO-BMN) with ethanol, pyridine, and triethylamine in hexane gives rise to a hydrogen bonding complex formation in a low concentration of ethanol (pyridine and triethylamine) at room temperature. For ethanol concentration &gt;5 mol dm−3, the H-bonded complex exhibits further interaction with another ethanol (pyridine and triethylamine) molecule leading to the formation of anion form of this compound. However, no excited-state proton transfer was observed in several solvents. HO-BMN is fairly fluorescent in a solid solution of boric acid glass at room temperature, as well as in the rigid organic solution at 77 K, but almost non-fluorescent in fluid media at room temperature (φ≈10−4). The non-radiative process of HO-BMN in fluid media is discussed in terms of torsional relaxation of the excited state.