bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotope Effect in Proton-Transfer and Association–Dissociation Reactions for Butylamine by Ultrasonic Relaxation Methods
Authors: Huang Hua , Nishikawa Sadakatsu , Dong Shaojun 
Published: November 2004

Abstract
Ultrasonic absorption coefficients were measured for butylamine in heavy water (D2O) in the frequency range from 0.8 to 220 MHz and at concentrations from 0.0278 to 2.5170 mol dm−3 at 25 °C; two kinds of relaxation processes were observed. One was found in relatively dilute solutions (up to 0.5 mol dm−3), which was attributed to the hydrolysis of butylamine. In order to compare the results, absorption measurements were also carried out in light water (H2O). The rate and thermodynamic parameters were determined from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength. The isotope effects on the diffusion-controlled reaction were estimated and the stability of the intermediate of the hydrolysis was considered while comparing it with the results for propylamine in H2O and D2O. Another relaxation process was observed at concentrations greater than 1 mol dm−3 in D2O. In order to examine the solution characteristics, proton NMR measurements for butylamine were also carried out in D2O. The chemical shifts for the γ- and δ-proton in butylamine molecule indicate the existence of an aggregate. From profiles of the concentration dependence of the relaxation frequency and the maximum absorption per wavelength of sound absorption, the source of the relaxation was attributed to an association–dissociation reaction, perhaps, associated with a hydrophobic interaction. The aggregation number, the forward and reverse rate constants and the standard volume change of the reaction were determined. It was concluded from a comparison with the results in H2O that the hydrophobic interaction of butylamine in D2O is stronger than that in H2O. Also, the isotope effect on this reaction was interpreted in terms of the solvent structure.
Calorimetric Studies on Antiferromagnetic and Structural Phase Transitions of the Metal-Assembled Complex MnCu(obbz)·5H2O
Authors: Asano Kaori , Inoue Kazuhiro , Nakano Motohiro , Miyazaki Yuji , Sorai Michio , Nakatani Keitaro , Kahn Olivier 
Published: November 2004

Abstract
Heat capacities of the molecule-based antiferromagnet MnCu(obbz)·5H2O (obbz = oxamidobis(benzoato)) have been measured at temperatures from 0.1 to 300 K by means of adiabatic calorimetry. A phase transition due to three-dimensional antiferromagnetic ordering was observed at 2.18 K, above which a heat capacity hump appeared, arising from the short-range ordering characteristic of a low-dimensional magnet. The enthalpy and entropy gained at the magnetic phase transition were evaluated to be 48.6 J mol−1 and 12.1 J K−1 mol−1, respectively. This entropy gain is close to the value R ln 5 ( = 13.4J K−1 mol−1) expected for the spin-manifold of the S = 2 ground state. The heat capacity hump above the magnetic transition temperature is explained well by the S = 2 one-dimensional ferromagnetic Heisenberg model with the exchange interaction J/kB = 0.75 K, where kB is the Boltzmann constant. These results confirm that the present complex behaves as a one-dimensional ferrimagnet, in which strong antiferromagnetic coupling exists between a pair of spins of Mn(II) (S = 5/2) and Cu(II) (S = 1/2) but the magnetic interaction is very weak between the pairs. A first-order phase transition was also found at 268.4 K. This transition may arise from orientational order–disorder mechanism of the crystalline water molecules in the complex.
Group-Theoretical Framework for Characterizing the Ring Flipping and N-Inversion of Piperidine Derivatives. Extended Pseudo-Point Groups and Subsymmetry-Itemized Enumeration
Authors: Fujita Shinsaku 
Published: November 2004

Abstract
The ring flipping (F) and the N-inversion (I) of piperidine are discussed by presuming a quadruplet of conformers as a model. After an extended pseudo-point group is defined, the concept of FI-energeticity is proposed. The flexible piperidine derivatives are enumerated on the basis of the model by the unit-subduced-cycle-index approach. The enumerated derivatives are classified into FI-isoenergetic (Types I, I′, and II) and FI-anisoenergetic (Types III and IV) by means of their extended pseudo-point groups.
Kinetics and Mechanism of Tris(pyridine-2-carboxylato)manganese(III) Reduction by Azide Ion in Sodium Pyridine-2-carboxylate–Pyridine-2-carboxylic Acid Buffer Media
Authors: Sen Gupta Kalyan Kali , Pal Biswajit , Bhattacharjee Nandini , Ghosh Saktiprosad 
Published: November 2004

Abstract
The kinetics and mechanism of the reduction of tris(pyridine-2-carboxylato)manganese(III) by azide ion in Na(pic)–picH [where Na(pic) = sodium salt of pyridine-2-carboxylic acid and picH = pyridine-2-carboxylic acid] have been studied. The reaction appears to proceed through the intermediate formation of a hepta-coordinated 1 : 1 complex between [MnIII(pic)3] and N3− ion, which then decomposes to give the free radical () and diaquabis(pyridine-2-carboxylato)manganese(II). The free radical further reacts with [MnIII(pic)3] to give nitrogen as the product of oxidation. During the reduction, pyridine-2-carboxylate ion is generated and the coordination sphere of the parent complex is altered, thereby indicating that the reaction takes place by an inner-sphere mechanism. The enthalpy change (ΔH°) and change in entropy (ΔS°) associated with the equilibrium step are −61 ± 4 kJ mol−1 and −169 ± 14 J K−1 mol−1, whereas the enthalpy of activation (ΔH≠) and the entropy of activation (ΔS≠) associated with the slowest step are found to be 91 ± 4 kJ mol−1 and 11 ± 14 J K−1 mol−1, respectively.
X-Ray Structural Characterization of [Eu(H2O)8]2[V10O28]·8H2O
Authors: Naruke Haruo , Yamase Toshihiro , Kaneko Masahiko 
Published: November 2004

Abstract
Europium decavanadate, [Eu(H2O)8]2[V10O28]·8H2O, crystallizes in triclinic, , a = 9.413(1), b = 9.885(1), c = 23.556(4)Å, α = 81.31(2), β = 82.08(2), γ = 89.51(2)°, V = 2145.8(5)Å3, Z = 2. There are two crystallographically independent [Eu(H2O)8]3+ cations and two centrosymmetric [V10O28]6− anions in a unit cell. Each [Eu(H2O)8]3+ cation achieves eight-fold coordination by aqua-ligands with an approximately square-antiprismatic configuration. The Eu–O distances for the [Eu(H2O)8]3+ cations were found to be 2.38(1)—2.54(1) Å (mean 2.44 ± 0.02 Å). The crystal structure consists of two crystallographically inequivalent [Eu(H2O)8]2[V10O28] layers and interstitial water molecules, the former being piled up alternately along the c-direction, and the latter linking the two adjacent layers with hydrogen-bonds.
Molecular Structure of a μ-Oxo Chromium–Iron Complex: Rare Example of a Crystallographically Characterized μ-Oxo Heterometallic Porphyrin
Authors: Oyaizu Kenichi , Haryono Agus , Nishimura Yukio , Yamamoto Kimihisa , Tsuchida Eishun 
Published: November 2004

Abstract
The crystal structure of a μ-oxo heterometallic porphyrin [(pip)(tpp)CrIIIOFeIII(tpp)] (pip = piperidine) not only confirmed the proposed oxidation state of chromium and iron atoms, but also revealed a unique coordination environment around chromium(III), which is substantially protruded from the porphyrin plane.
Ion Association of Primary Ammonium Ions with Aromatic Anions by Capillary Zone Electrophoresis
Authors: Takayanagi Toshio , Wada Eiko , Oshima Mitsuko , Motomizu Shoji 
Published: November 2004

Abstract
Ion associability of some alkylammonium-type ion association reagents with the positional isomers of aromatic anions has been examined in an aqueous solution through electrophoretic mobility changes of the corresponding anions in capillary zone electrophoresis. Ion associability of the alkylammonium ions was investigated for monovalent and divalent cationic groups, considering the hydrophilicity and hydrophobicity of cationic groups and the hydration of the ionic sites. When such monovalent cationic reagents as hexylmethylammonium, hexyltrimethylammonium, and hexyltriethylammonium ions were used, the ion associability increased with an increase in the number and bulkiness of alkyl groups of the cations. On the other hand, hexylammonium ion, a primary ammonium ion, showed different behavior: Higher ion associability was obtained with aromatic anions possessing two carboxylate groups at adjacent positions. Also ion associability of the primary diammonium ions with phthalate and naphthalene-2,3-dicarboxylate ions was the highest among their positional isomers, which was the reverse behavior from that obtained with quaternary diammonium ions. Such characteristic ion associability in the primary ammonium ions could be explained from the hydrophilicity of the ionic groups of the pairing ions: A primary ammonium group is more ion associable with hydrophilic anionic groups.
Synthesis of Tetracyano(S-2-aminomethylpyrrolidine) and Tetracyano(2-aminomethylpiperidine) Complexes of Fe(II) and Co(III): Stereochemistry and Comparison of Spectroscopic Properties of Isoelectronic Structures
Authors: Goto Masafumi , Tsuruda Nobuhiro , Fujioka Sachiko , Kurosaki Hiromasa 
Published: November 2004

Abstract
Sodium tetracyano((S)-2-aminomethylpyrrolidine = S-pyrda)ferrate(II) and -cobaltate(III) and tetracyano(2-aminomethylpiperidine = pipda)ferrate(II) and -cobaltate(III) were prepared. These complexes afforded well-separated 1H NMR spectra sufficient to delineate their structures in solution. The major conformation of the coordinated pyrda and pipda differs in the condensation mode of the five-membered chelate ring and the heterocycles, i.e. cis- and trans-, respectively, this leads to the different orientation of the heterocycle of the diamines. The comparison of the 1H and 13C chemical shifts and the electronic structure is described from the viewpoint of the isoelectronic structures with different electric charges.
Single Amino Acid Preferences for Specific Locations at Type-I α-Turns in Globular Proteins
Authors: Narita Mitsuaki , Sode Koji , Ohuchi Shokichi 
Published: November 2004

Abstract
Using both dihedral angles and hydrogen-bond definitions, 225 type-I α-turns were extracted from 125 analyzed proteins. The extracted α-turns were built up from 5% (1125) of the total amino acid residues (23286) found in the proteins. The type-I α-turn is an independent kind of secondary structural unit, although it has been frequently classified as (i, i+1) double β-turns. Both the nucleation of a helix with the type-I β-turn and its propagation with the repetitive addition of the type-I β-turn suggest that the origin of the helix in a globular protein might be the type-I β-turn. Single amino acid preferences for specific locations at type-I α-turns were compared to those at type-I β-turns and the ends of helices. The result indicates that the type-I α-turn, the type-I β-turn, and the helix are of similar kin. Similarities in the structure and amino acid preferences for specific locations among them suggest that the amino acid residues on defined positions along both turns could be properly assigned to the corresponding helix elements.
Synthesis of Two Possible Disulfide Bonds Containing Peptide Fragments (Cys6–Cys47, Cys48–Cys52 (Type I), and Cys6–Cys48, Cys47–Cys52(Type II) of h-IGF-I) for the Identification of Disulfide Bond Linkage in Recombinantly Produced h-IGF-I
Authors: Iwai Michio , Yamada Hisashi , Ishii Yoshinori , Tamura Kouichi , Niwa Mineo , Kobayashi Masakazu 
Published: November 2004

Abstract
The primary structure of human IGF-I, except for the disulfide bond system, has been reported by Rinderknecht and Humbel. IGF-I afforded the corresponding characteristic peptide fragments on V8 protease digestion, which contained Cys6, Cys47, Cys48, and Cys52. Two possible fragments, Type I with Cys6–Cys47 and Cys48–Cys52 and Type II with Cys6–Cys48 and Cys47–Cys52 of h-IGF-I(4-9,47-53), were chemically synthesized. The disulfide bond system of IGF-I was unequivocally determined to be the Type-II form along with Cys18–Cys61. Interestingly, the Type-I system was included in the disulfide bond isomer produced as the main by-product in the refolding step on IGF-I synthesis by the recombinant DNA method.
Palladium(II)-Catalyzed Aryl Coupling of Triarylbismuthines under Air
Authors: Ohe Toshiyuki , Tanaka Takumi , Kuroda Masashi , Cho Chan Sik , Ohe Kouichi , Uemura Sakae 
Published: November 2004

Abstract
Triarylbismuthines readily reacted with a catalytic amount of palladium(II) acetate in methanol under air to give the corresponding biaryls in high yields. The presence of oxygen was indispensable for this catalytic coupling, biaryl formation being quite slow under nitrogen. Oxygen absorption was observed during the reaction and a Pd-oxygen complex prepared separately worked effectively as a reagent for this coupling even under inert gas.
Effect of Benzylic Methyl Groups on Kinetic Basicity of Amine Ligand in o-Boron Substituted N,N-Dimethylbenzylamines
Authors: Toyota Shinji , Asakura Mitsuhiro , Futawaka Tadahiro , Oki Michinori 
Published: November 2004

Abstract
Rates of the dissociation of the intramolecular B–N coordination bond in two series of phenylborane derivatives, the boronate and diethylborane complexes, with –CHMeNMe2 or –CMe2NMe2 group at the o-position were determined by the NMR lineshape analysis or saturation transfer method. The new organoboron compounds were synthesized from the corresponding organolithium compounds with appropriate boron reagents. Comparison of the kinetic data with those of the –CH2NMe2 compounds reveals that the barrier height to the dissociation, namely the kinetic basicity of the amine ligand, is increased as the molecule possesses more methyl groups at the benzylic position for both of the series of boron compounds. The X-ray structure of one of the boronate complexes and the NMR titration measurements of model amines indicate that the basicity of the amine ligand is not affected much by the methyl substitution in the coordinated form. Therefore, the substituent effect on the kinetic basicity is mainly ascribed to the destabilization of the transition state by the geminal dimethyl groups rather than to any inductive or steric effects at the initial state, especially for the –CMe2NMe2 compounds.
Synthesis and Electronic Properties of d8 Transition-Metal Complexes of Vinylene-Bridged Bis- and Tris(octaethylporphyrin)s
Authors: Higuchi Hiroyuki , Shinbo Masatoshi , Usuki Masanobu , Takeuchi Makoto , Hasegawa Yutaka , Tani Keita , Ojima Juro 
Published: November 2004

Abstract
Complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)–M and tris(OEP)–M) with d8 transition-metal ions (M = Ni(II), Pd(II), and Pt(II)) were synthesized. Metalation of (E)-bis(OEP)–H2 was carried out under the same conditions as for the corresponding octaethylporphyrin complex (OEP–M), to afford a mixture of complexes bearing the vinylene-linkages with (E)- and (Z)-configurations. On the other hand, metalation of tris(OEP)–H2 afforded the single product of which two vinylene-linkages remained holding the same (E,E)-configuration as that in the free-base. 1H NMR spectra varied more drastically for (Z)-bis(OEP)–M, with respect to those of OEP–M, while electronic absorption spectra did more drastically for the (E)-isomers. Their electronic properties at the ground state were examined, proving that the interaction between the constituent OEP rings through the vinylene-linkages is more intensive for tris(OEP)–M than for bis(OEP)–M and more intensive for the Ni complex than for the Pd and Pt ones.
Syntheses of Dialkali Metal Complexes of Tetrakis(dimethylsilyl)ethylene: [(HMe2Si)2C=C(SiMe2H)2]2−[M+(ligand)n]2. Evidence for SiH–Alkali Metal Agostic Interactions
Authors: Ichinohe Masaaki , Sekiguchi Akira , Takahashi Masae , Sakurai Hideki 
Published: November 2004

Abstract
A series of dialkali metal complexes, [(HMe2Si)2C=C(SiMe2H)2]2−[M+(ligand)n]2 (M = Li, Na, K, Rb, Cs), were prepared by the reaction of tetrakis(dimethylsilylethylene) with alkali metals. These complexes exhibit Si–H alkali metal agostic interactions and have been characterized by spectroscopic and structural methods. Spectroscopic evidence for the interaction of the hydrogen on the silicon atom with alkali metals include (1) an unusually small value of the silicon-hydrogen coupling constant (1JSi–H) in NMR spectra and (2) low-energy Si–H stretching frequency in the infrared spectra. The smallest cation, Li+, can interact with SiH most strongly.
Thiophene 1,1-Dioxide: Synthesis, Isolation, and Properties
Authors: Nagasawa Hidehiro , Sugihara Yoshiaki , Ishii Akihiko , Nakayama Juzo 
Published: November 2004

Abstract
Oxidation of thiophene with dimethyldioxirane at −20 °C and removal of the solvent and volatile materials below −40 °C allowed the isolation of the parent thiophene 1,1-dioxide (1) as colorless crystals in pure form. The 1,1-dioxide 1, which had eluded isolation for a long time despite many efforts, melted at about 6 °C and the melt solidified at room temperature because of the dimeric and trimeric products formation. The structure of 1 was fully characterized by 1H- and 13C NMR, IR, Raman, UV/vis, and Mass spectroscopies. The decomposition of 1 in solution provided the dimer (7) as the principal product along with the trimer (9), whereas the decomposition of a neat sample furnished 7 and 9 in comparable amounts. The half-life of 1 is dependent upon the concentration of 1; 137 and 747 min at 25 °C in 0.12 and 0.025 M CDCl3 solutions (1 M = 1 mol dm−3), respectively. Kinetics of the dimerization of 1 in a dilute solution provided the activation parameters of Ea = 64.4 (±0.3) kJ mol−1, ΔH≠ = 62.0 (±0.3) kJ mol−1, and ΔS≠ = −59.8 (±1.0) J K−1 mol−1. Attempted reactions of 1 with a series of dienophiles and dienes all failed because the dimerization of 1 is much faster than reactions with these additives. An exception is the reaction with cyclopentadiene which gave the Diels–Alder adduct in good yield. The adduct of the dimer 7 with dimethyl acetylenedicarboxylate was found to undergo a retro Diels–Alder reaction to regenerate 1.
The Kinetics and Mechanism of Interaction of Fe40Ni40B20 Amorphous Metallic Alloys with Mineral Acid Media
Authors: Košturiak Adam , Valko Ladislav , Polavka Jirí , Brutovsky Milan , Morris Harry 
Published: November 2004

Abstract
The paper emphasizes the importance of amorphous metallic alloys thin films for magnetic coatings as well as their characterisation with respect to the mineral acid medium in a more qualitative way. The kinetics and mechanism of the interaction of Fe–Ni–B amorphous alloys films with various concentrations of mineral acids (o-phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid,) were studied. On the basis of the weighing method used we deduced that the overall physically and chemically complicated process consists of simultaneous formation of oxides on the surface of the thin films, their dissolution and moreover dissolution of the metal (Fe, Ni) and metalloid (B) elements through a tendency of all of them to react with hydrogen ions. It should be stressed that dissolution of the two-dimensional amorphous metallic alloys-ribbons significantly differs from such dissolution of the metal bulk systems.
Liquid Crystalline Phase Transition in Organophosphazenes with 4-Octyloxybiphenyl Mesogenic Groups
Authors: Moriya Keiichi , Suzuki Toshiya , Mizusaki Hiroshi , Yano Shinichi , Kajiwara Meisetsu 
Published: November 2004

Abstract
Cyclotriphosphazenes with the same 4-octyloxybiphenyl mesogenic side groups have been synthesized and were studied their phase transition and liquid crystallinity using DSC measurements and polarizing microscope observations. We found an enantiotropic smectic C phase in hexakis(4-(4′-octyloxy)biphenoxy)cyclotriphosphazene but no liquid crystalline phase was observed in octakis(4-(4′-octyloxy)biphenoxy)cyclotetraphosphazene. These may originate from each of the three side chains of the cyclotriphosphazene molecules pointed upwards and downwards perpendicularly from the cyclotriphosphazene ring, which helps the formation of the liquid crystalline layer structure. However, in the cyclotetraphosphazene, the eight side chains orient relatively at random and this prevents the formation of the mesogenic layer structure.
Photoinduced Electron Transfer Reaction of 3,3-Dimethyl-3H-pyrazoles: The Formation of Solvent Adducts through Cyclopropene Derivatives
Authors: Miyagawa Nobukazu , Karatsu Takashi , Kitamura Akihide 
Published: November 2004

Abstract
3,3-Dimethyl-3H-pyrazoles were photolyzed, and in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate (TPP+) as a sensitizer in acetonitrile; in addition to cyclopropenes, 2H-pyrroles were obtained as solvent adducts to 1,3-radical cation intermediate.
Photolysis of C60 with Cyclic Amino Acids: Preparation of Dihydrofullerenes by Decarboxylation
Authors: Zhang Wen , Su Yang , Gan Liangbing , Jiang Jianfeng , Huang Chunhui 
Published: November 2004

Abstract
Photolysis of C60 with piperidinoacetic acid and morpholinoacetic acid results in the decarboxylation of the acids and formation of the 1,2-dihydrofullerenes C60(H)[CH2N(CH2)5] 1, C60(H)[CH2N(CH2CH2)2O] 2. Under the same conditions the reaction with the methyl esters of the two cyclic amino acids give the fullerropyrrolidine derivatives C60[CH(CH2)4NCHCOOCH3] 3, C60[CH(CH2OCH2CH2)NCHCOOCH3] 4.
Preparation of Sigmatropic 2-Acyloxy-5-perfluoroalkoxytropones: New Monocyclic Troponoid Liquid Crystals with an Enantiotropic Smectic A Phase
Authors: Mori Akira , Takematsu Shinji , Takeshita Hitoshi 
Published: November 2004

Abstract
Monocyclic sigmatropic troponoid liquid crystals with a 2-(perfluoroalkyl)ethoxyl group at C-5 showed an enantiotropic smectic A phase. They have higher melting and clearing points than the corresponding non-fluorinated compounds, which exhibit a monotropic smectic A phase.
Stereoselective Epoxidation of Acyclic Allylic Ethers Using Ketone-Oxone® System
Authors: Kurihara Masaaki , Ishii Kei , Kasahara Yoko , Kameda Mari , Pathak Ashish K , Miyata Naoki 
Published: November 2004

Abstract
The stereselective oxidation of acyclic allylic silyl ethers with dioxiranes generated in situ from Oxone® and ketones provided erythro epoxides.
Synthesis of Dipyridinyls and Terpyridinyls with Phenyl Spacers through Base Induced Ring Transformation Reactions
Authors: Ram Vishnu J , Goel Atul 
Published: November 2004

Abstract
A novel approach to the synthesis of dipyridinyls (3a,b, 5a,b, 6c,d) and terpyridinyls (6a,b, 7a,b) with phenyl and 1,3-terphenyl spacers is delineated by base induced ring transformation reactions of 6-pyridyl-3-carbomethoxy-4-methylthio-2H-pyran-2-ones.
Integrated Chemical Process. One-Pot Preparation of Acetylenes by Peterson-Sulfone Elimination
Authors: Orita Akihiro , Yoshioka Naonori , Otera Junzo 
Published: November 2004

Abstract
Integration of silylation of α-sulfonyl carbanion, addition of the anion of the resulting α-silyl sulfone to aldehyde, Peterson elimination, and sulfone elimination leads to one-pot synthesis of acetylenes.
Construction of a Novel Chemical Model for the Nerve Transmission System Using Self-Oscillating Multi-Phases Liquid Membrane System
Authors: Yoshihisa Hiroshi , Miyamura Kazuo , Gohshi Yohichi 
Published: November 2004

Abstract
A novel multi-phases liquid membrane system, which has two aqueous phases with surfactant, is found to exhibit a synchronisation of the oscillation. Detailed investigation revealed the resemblance of the system with the nerve transmission system.
Lanthanide Triflate-Catalyzed Three-Component Coupling Reactions of Aldehydes, Hydroxylamines, and Alkenes Leading to Isoxazolidine Derivatives
Authors: Shu Kobayashi , Akiyama Ryo , Kawamura Mikako , Ishitani Haruro 
Published: November 2004

Abstract
Three-component coupling reactions of aldehydes, hydroxylamines, and alkenes proceeded smoothly in the presence of a catalytic amount of a lanthanide triflate, to afford isoxazolidine derivatives in high yields with high diastereoselectivities. The asymmetric 1,3-dipolar cycloaddition using a chiral lanthanide catalyst is also described.