bluuebunny/crossref_metadata_2025_split huggingface dataset:
Empirical Formula for Mass Transfer across the Boundary between Convections in a Two-layer System
Authors: Kamakura Katsuyoshi 
Published: July 2006

Abstract
When a two-layer system which consists of water (upper layer) and an aqueous solution (lower layer) is heated from one side and cooled from the opposite side, a convection starts in each layer and a sharp horizontal boundary is formed by the two flows in opposite directions. The empirical formula for the transfer of a solute across the boundary was obtained by measuring the change in the concentration of a solute in the upper layer. The flux, WA, of a solute, A, was expressed by
W A=a3(Δρ1–Δρ0)D0.5(ΔcI⁄Δρ2).
Here, a3 is the mass-transfer coefficient; Δρ1, the density difference between the liquid on the heated wall and that on the cooled wall; Δρ0, the value of Δρ1 at which the convections start; D, the diffusion coefficient of a solute; and ΔcI and Δρ2, the concentration difference and the density difference, respectively, between the solution of the upper layer and that of the lower layer.
Raman Spectra of Alkali Metal Oxalates in Aqueous Solution. Evidence for Ion-pair Formation
Authors: Kanamori Kan , Mihara Masamitsu , Kawai Kiyoyasu 
Published: July 2006

Abstract
Laser Raman spectra of aqueous solutions of lithium, potassium, and caesium oxalates have been obtained; their band contours were examined by curve analysis. The intensities of several bands show distinct concentration and cation dependences. This behavior is connected with the ion-pair formation of oxalate ions with alkali metal cations. The assignments of C=O stretching vibrations are also discussed.
Thermodynamic Study of the Self-association of 6-Methylpurine in Water-1,4-Dioxane Solvent
Authors: Morimoto Satoshi 
Published: July 2006

Abstract
Determination of the thermodynamic quantities of the self-association of 6-methylpurine in water(1)–1,4-dioxane(2) (x2=0–0.36) mixed solvent has been made from heat of dilution measurements in various organic contents, at 25 °C. It was confirmed experimentally that the dissociation process of associating purine bases in solution is very fast by dilution. It was characteristic of this solvent system that the standard enthalpy and entropy changes, ΔH° and ΔS°, of the association exhibited an abrupt behavior. These values decrease remarkably with 1,4-dioxane content up to a water-rich solvent composition below x2=0.012. After that, they approach their relatively high values for the pure organic component, at first with a steep slope, later more gradually. This behavior is related to the structural changes of the solvent in an extremely sensitive way. In the case of water (1)–methanol(2) (x2&lt;0.19) mixed solvent system which has been investigated for comparison with the above system, minimum values of the same kind were found in the vicinity of x2=0.12, at 25 °C.
Differential Determination of Tellurium(IV) and Telluriiim(VI) by Atomic Absorption Spectrophotometry after Hydride Generation. Combined Use of Titanium(III) Chloride as a Prereductant and Sodium Borohydride Solution
Authors: Jin Kazuo , Taga Mitsuhiko , Yoshida Hitoshi , Hikime Seiichiro 
Published: July 2006

Abstract
Sensitive determination of tellurium was investigated by atomic absorption spectrophotometry after hydride generation and differential determination of tellurium(IV) and tellurium(VI) in acidic solution was carried out. When sodium borohydride solution is used without any prereductant, only the signal from tellurium(IV) is obtained. On the other hand, when titanium(III) chloride solution is added before the addition of borohydride solution, total signal from tellurium(IV) and tellurium(VI) can be obtained; 30—60 s of prereduction is required. The effectiveness of the titanium(III) chloride-borohydride reduction system is shown in the interference study. The interference of selenium(IV) is eliminated up to 200 fold vs. 0.25 μg of tellurium(IV) in 20 cm3 of 3 mol dm−3 hydrochloric acid by the use of 2 cm3 of 5% w/v titanium(III) chloride solution as a prereductant. Tellurium in steel and sulfur (commercial reagent) can be determined satisfactorily without isolation of tellurium from matrix by this method. Detection limit of the method is 8 ng. The coefficient of variation of the method is 2.4% in the ten determinations of 0.25 μg of tellurium.
Studies of the Metal Complexes of Cyclohexane Derivatives. VI. The Thermal Transformation of Nickel(II) Complexes of 1,2-Cyclohexanediamine Isomers
Authors: Saito Reiko , Kidani Yoshinori 
Published: July 2006

Abstract
The thermal transformations of the following three types of nickel(II) complexes were investigated by means of TG-DSC analyses: [Ni(t-chxn)2(H2O)2]X2, [Ni(c-chxn)3]X2·nH2O, and [Ni(t-chxn)3]X2·nH2O (X=Cl−, Br−, and NO3−), where c- and t-chxn denote cis- and trans-1,2-cyclohexanediamine respectively. The distorted octahedral [Ni(t-chxn)2(H2O)2]X2 complexes (X=Cl− and Br−) are thermally deaquated to form yellow complexes, which then turn into parental diaquabis-complexes in the air at room temperature. [Ni(t-chxn)2(H2O)2] (NO3)2 undergoes a thermal deaquation-anation reaction. The octahedral tris(c-chxn) complex is converted into a square planar bis(c-chxn) one by the evolution of one molecule of the ligand upon heating, whereas tris(t-chxn) complex became a distorted octahedral bis(t-chxn) one with anion coordination. In this paper, the stereochemical thermal changes of the complexes in the solid state will be discussed with regard to the steric configuration of the ligands.
Acetoxymethylation of Coumarins by Manganese(III) Acetate
Authors: Kurosawa Kazu , Harada Hironobu 
Published: July 2006

Abstract
The reactions of 4-methoxy-, 7-methoxy-, 6,7-dimethoxy-, and 7,8-dimethoxycoumarins with manganese(III) acetate in boiling acetic acid containing acetic anhydride gave 3-(acetoxymethyl) coumarins as the major product. The reactions of coumarin, and 6-methoxy- and 8-methoxycoumarins with manganese(III) acetate yielded a mixture of 3-(diacetoxymethyl)- and nuclear acetoxymethylated coumarins. The reaction of 7-methoxycoumarin with lead(IV) acetate gave 7-methoxy-3-methylcoumarin.
Electron-organic Chemistry. IV. Structure—Anodic Potential Relationship and Electron-transfer-induced Reactions of [2.2]Para- and -Metaparacyclophanes
Authors: Sato Takeo , Torizuka Koichi , Shimizu Motomu , Kurihara Yukio , Yoda Noriko 
Published: July 2006

Abstract
The anodic peak potentials of [2.2]para- and -metaparacyclophanes were found to be highly dependent on the solvent. A cleavage reaction occured when [2.2]paracyclophane was electrolyzed anodically, using acids or alcohols as nucleophilic solvents, whereas lead tetraacetate oxidation in trifluoroacetic acid–dichloromethane gave nuclear substitution products. The cathodic reduction in hexamethylphosphoric triamide–lithium chloride–acetic acid gave 1,2-di-p-tolylethane and its Birch reduction products. On anodic oxidation, [2.2]metaparacyclophane gave a rearrangement reaction product, 4-hydroxy[2.2]metacyclophane. Possible reaction pathways for these reactions were formulated.
A Study of Catalysis by Metal Phosphates. V. The Alkylation of Toluene with Methanol over Metal Phosphate Catalysts
Authors: Sodesawa Toshiaki , Kimura Isao , Nozaki Fumio 
Published: July 2006

Abstract
The side chain alkylation of toluene with methanol over the catalyst of Ca3(PO4)2 or K3PO4 supported on active carbon gave more ethylbenzene than that over MgO. It was found that there are correlations between the catalytic activities and acid-base properties.
Rayleigh Ratio for Benzene and Its Temperature Dependence
Authors: Kamata Toshio , Nakahara Hisae 
Published: July 2006

Abstract
The temperature dependence of the Rayleigh ratio for benzene was studied for the purpose of comparing various reported values obtained at different temperatures with each other. The following relationship was obtained for a wavelength of incident light of λ0=435.8 nm:
R 90=(0.1377t+43.06)×10−6cm−1
where t is temperature (°C). Light-scattering photometers were calibrated with benzene purified by a preparative gas chromatograph by using a value of the Rayleigh ratio for benzene of R90=46.5×10−6cm−1 (25 °C, λ0=435.8 nm). In order to verify the validity of the calibrations, molecular weight determinations were run on three standard substances: egg white lysozyme, raffinose, and sucrose. The temperature of benzene was directly measured by inserting the sensor of a thermistor thermometer into the benzene within the cell.
Emission Spectra of 1,4-Naphthoquinone and Its 2-Methyl Derivative in the Vapor Phase
Authors: Itoh Takao , Baba Hiroaki 
Published: July 2006

Abstract
The emission spectra of 1,4-naphthoquinone (NQ) and 2-methyl-1,4-naphthoquinone (MNQ) vapors have been investigated at various temperatures in the presence of added foreign gases (≈100 Torr). The results indicate that in both NQ, and MNQ, the emission consists of T1(n, π*)→S0 phosphorescence and weak E-type delayed fluorescence, S1(n, π*)→S0, the latter lying at higher frequencies. This new interpretation of the vaporphase emission spectra of the naphthoquinones, which is substantially different from the interpretations given by previous authors, is based on and consistent with the following observations: (1) When the temperature is raised, the ratio of the fluorescence intensity to the phosphorescence intensity increases; (2) the S1–T2 energy separations, 1365±60 and 1500±200 cm−1 for NQ, and MNQ, respectively, determined from the temperature dependence of the emission intensities agree with the corresponding values obtained from spectral data; (3) the emission lifetimes obtained by monitoring the fluorescence and phosphorescence are identical.
Resistmetric Study of the Potential-sensitive Surface Layer Formed on VO2 Electrode in a Neutral Solution
Authors: Nakamura Toyohisa , Haruyama Shiro 
Published: July 2006

Abstract
The formation of a potential-dependent surface layer on VO2 electrode has been investigated from the change in conductance of a thin VO2 film electrode by galvanostatic polarization. The VO2 electrode dissolved as vanadate with 100% current efficiency by anodic polarization. At potentials negative to the immersion potential, the VO2 electrode functioned as an insoluble electrode with the formation of the potential-dependent surface layers of the vanadium oxides by lower valence. The change in composition of the surface layers was traced by resistmetry and coulometry, and illustrated against the amount of electric charge passed, taking V7O13, V6O11, V5O9, V4O7, V3O5, and V2O3 as the possible oxides. The composition at vanadium oxides of outer-most layer was plotted against the electrode potential. The plot shows a multi-step figure as in the equilibrium partial pressures of oxygen on vanadium oxides at high temperatures, suggesting a model in which the composition of the outer-most layer of the oxide responds to the electrode potential applied.
Hydrogen-Deuterium Equilibration Reaction over Platinum Supported on Polyamide-6
Authors: Inoue Yasunobu , Hacho Seiji , Miyazaki Eizo , Yasumori Iwao 
Published: July 2006

Abstract
Catalysis by platinum supported on polyamide-6 was examined for the H2-D2 equilibration reaction at 0 °C in the pressure range of 5–20 Torr (1 Torr=133.3 Pa). Three kinds of polyamides with different molecular weights were prepared as support; the concentration of platinum varied from 0.5 to 2.7 wt%. With preadsorption of hydrogen at 0 °C, the rate of the reaction was found to increase up to 10 times as high as the original level. The rate km (HD molecule s−1Pt atom−1) showed a maximum, depending on surface area of the polyamides used, in the range 0.8–1.0 wt% of Pt content and its dependence on total pressure is represented by km=K1P⁄(1+K2√‾P)2 irrespective of Pt content. No significant isotope effect was observed at 0 °C. It was found that a linear relationship exists between the enhancement of km and the amount of hydrogen preadsorbed, indicating an important role of the preadsorbed hydrogen in activation of the catalysts. In contrast to km, the turn-over frequency kt (HD molecule s−1 site−1) was nearly independent of Pt concentration. The exchange reaction is explained in terms of the Bonhoeffer-Farkas mechanism. XPS spectra provided the evidence for the presence of Pt(II) complexes on the surface. The structure of active sites is discussed.
The Origin of the Polarity of a Radical in Hydrogen Abstraction Reactions
Authors: Shinohara Hiroyuki , Imamura Akira 
Published: July 2006

Abstract
The electrophilicity of the H atom in hydrogen abstraction reactions was studied by the CNDO/2 method. The origin of the electrophilicity of the H atom was well understood using the stabilization energy due to the delocalization of electrons (SEDE) between the radical and substrate; this energy was calculated along the reaction path. The electrophilic energy (SEDE from the substrate to the radical) governs the relative reactivities of substrates, CH4&lt;CH3CH3&lt;CH3CH2CH3&lt;(CH3)3CH which correspond to the order of the increase in the electron density. The electrophilic energy is also important in hydrogen abstraction by the H atom from aliphatic alcohols. In the case of the Cl2− radical, the nucleophilic energy (SEDE from the radical to the substrate) determines the relative reactivities of substrates, CH3OH&lt;C2H5OH&lt;i-C3H7OH. The polarity of a free radical is tentatively clarified by using its ionization potential.
The Crystal Structure and Absolute Configuration of (−)589-Bis(2,4-pentanedionato)(1,3-propanediamine)chromium(III)Iodide Monohydrate
Authors: Matsumoto Keiji , Ooi Shun’ichiro 
Published: July 2006

Abstract
The crystal structure of (−)589-[Cr(acac)2(tn)]I·H2O has been determined from the X-ray diffraction data collected on a diffractometer. The crystal is orthorhombic, with the space group P212121 and with a=20.834(6), b=12.015(3), c=7.621(2) Å, and Z=4. Block-diagonal least-squares refinement for 1426 independent reflections with Fo2&gt;3σ(Fo2) converged to R=4.91%. The complex cation has the Λ absolute configuration. The 1,3-propanediamine ligand assumes a chair conformation. One of the 2,4-pentanedionato chelate rings is almost planar, while in the other the 2,4-pentanedionato plane is bent away from the plane defined by Cr and 2 O donor atoms because of the intramolecular repulsion, the interplanar angle being 9.4°. The interrelation between the absolute configuration and the circular dichroism was discussed for the [Cr(acac)n(tn)3−n](3−n)+-type complexes.
Quantification of Phenols in Gas from Rotten Liquid Swine Manure by Computer-controlled Gas Chromatography-Mass Spectrometry
Authors: Yasuhara Akio , Fuwa Keiichiro 
Published: July 2006

Abstract
Analytical studies on phenol, o-cresol, m-cresol, p-cresol, and p-ethylphenol from liquid swine manure were performed with selected ion monitoring in computer-controlled gas chromatography-mass spectrometry. Phenol, p-cresol, and p-ethylphenol in effluent gas from liquid swine manure and in the head-space gas over liquid swine manure were determined.
Pyrrolizidine Alkaloids. The Synthesis and Absolute Configuration of All Stereoisomers of Monocrotalic Acid
Authors: Matsumoto Takashi , Takahashi Makoto , Kashihara Yutaka 
Published: July 2006

Abstract
All stereoisomers (3a, b–6a, b) of monocrotalic acid have been synthesized. Methylation of (±)-cis-2,3,4-trimethyl-2-pentenedioic acid with diazomethane followed by cis-hydroxylation with potassium permanganate afforded two epimeric γ-lactone esters in a ratio of ca. 1:5. These esters were then hydrolyzed with dilute hydrochloric acid to the corresponding acids, (±)-3 and racemic monocrotalic acid (4). Optical resolution of (±)-3 with brucine afforded 3a (2R,3R,4S) and 3b (2S,3S,4R). The racemic monocrotalic acid was also resolved by means of brucine to give natural monocrotalic acid (4a: 2R,3R,4R) and its enantiomer (4b: 2S,3S,4S). Subsequently, (±)-trans-2,3,4-trimethyl-2-pentenedioic acid was resolved with cinchonidine to give 8a and 8b, whose stereochemistry was assigned respectively as S- and R-configuration by correlation to the known (R)-(−)-2-phenylpropanoic acid. Methylation of 8a followed by cis-hydroxylation and hydrolyses afforded γ-lactone acids, 5a (2R,3S,4S) and 6b (2S,3R,4S). Similarly, the enantiomer 8b was also converted into the corresponding acids, 5b (2S,3R,4R) and 6a (2R,3S,4R). The stereochemical course of the above hydroxylations with potassium permanganate was well explained by a modification of Gram’s rule of asymmetric induction. The CD spectra of 3a,b–6a,b were also discussed.
Super Exchange in Copper(II) Dimers. II. Synthesis, Characterization and Magnetic Properties of Binuclear Adducts of Copper(II) Halides with 1,2-Benzoquinone Dioximes. Ligandinduced Ferromagnetic Exchange Coupling
Authors: Bélombé Michel Megnamisi 
Published: July 2006

Abstract
Various 1,2-benzoquinone dioximes (bqdH) have been combined with CuCl2 or CuBr2 to afford the following new dimeric adducts: di-μ-chlorobis[chloro(1,2-benzoquinone dioxime)copper(II)], [CuCl2(bqdH)]2; di-μ-chlorobis[chloro(4-chloro-1,2-benzoquinone dioxime)copper(II)], [CuCl2(ClbqdH)]2; di-μ-chlorobis[chloro(4-methyl-1,2-benzoquinone dioxime)copper(II)], [CuCl2(MebqdH)]2; di-μ-chlorobis[chloro(4,5-dimethyl-1,2-benzoquinone dioxime)copper(II)], [CuCl2(Me2bqdH)]2; di-μ-bromobis[bromo(1,2-benzoquinone dioxime)copper(II)], [CuBr2(bqdH)]2; di-μ-bromobis[bromo(4-chloro-1,2-benzoquinone dioxime)copper(II)], [CuBr2(ClbqdH)]2; di-μ-bromobis[bromo(4,5-dimethyl-1,2-benzoquinone dioxime)copper(II)], [CuBr2(Me2bqdH)]2. These brown solids were characterized by variable-temperature magnetic susceptibility measured within 4.2–300 K, as well as by room temperature near infrared and electron spin resonance spectra from which the dimeric structure of the compounds was inferred. The intradimer magnetic exchange interaction was found to occur by a super exchange mechanism mediated by the valence p wave functions of the bridging halide ions. It was observed that the electrophilic character of the benzoquinonoid ligands affects the magnetic exchange via backbonding and through mesomeric π electron delocalization. It was found, most interestingly, that the tendency to ferromagnetic exchange interaction within a dimer is the stronger, the more electrophilic the bqdH ligands can be made.
Photoisomerization of Bis(t-butyl isocyanide)dichlorobis-(triphenylphosphine)ruthenium(II)
Authors: Tsuihiji Tamotsu , Akiyama Takeo , Sugimori Akira 
Published: July 2006

Abstract
UV-irradiation of bis(t-butyl isocyanide)dichlorobis(triphenylphosphine) ruthenium(II) brings about isomerization. The composition of the photo-stationary state is wavelength-dependent. A mechanism via the photoelimination of triphenylphosphine is proposed.
The Molecular and Crystal Structure of the Green Form of Bis(N-cyclohexylsalicylideneaminato)copper(II)
Authors: Tamura Hatsue , Ogawa Kazuhide , Takeuchi Akira , Yamada Shoichiro 
Published: July 2006

Abstract
Bis(N-cyclohexylsalicylideneaminato)copper(II) crystallizes in two forms: one is a brown crystal (Form I), and the other is a green one (Form II). The crystal structure of Form II has been determined by X-ray analysis. The green crystals are monoclinic; space group, P21/n. The cell dimensions are a=23.134(6), b=9.525(3), c=21.472(8) Å, β=99.42(1)°, and Z=8. The structure was deduced by the heavy-atom method and was refined to a final R value of 0.082 for 1883 observed reflections by the block-diagonal least-squares method. The molecular structure in Form II is dimeric, in contrast with the case of Form I, which is composed of a monomeric molecule. The two monomeric halves are joined by two Cu–O bonds with distances of 2.60(1) and 2.64(1) Å. Each copper(II) ion is penta-coordinated in a distorted square-pyramidal configuration. The molecular structures in Form I and II have been compared with those of the related Cu(II) compounds.
Kinetics of Ligand Exchange between Tris(acetylacetonato[2-14C])cobalt(III) and Acetylacetone in Acetonitrile, Evidence for SN1 Mechanism
Authors: Kido Hiroaki , Saito Kazuo 
Published: July 2006

Abstract
Tris(acetylacetonato[2-14C]) cobalt (III) undergoes ligand isotopic exchange with acetylacetone (Hacac) in acetonitrile at 85–100 °C without decomposition and solvolysis. The exchange rate is proportional to the complex concentration (0.002–0.007 M, 1 M=1 mol dm−3), the first-order rate constant ko being independent of [Hacac] (0.001–0.97 M). ko=1.6×10−5 s−1 at 93.2 °C. The activation enthalpy and entropy are 38±4 kcal mol−1 (1 cal= 4.18J) and 23±8 cal K−1 mol−1, respectively. Trichloroacetic acid (&lt;0.02 M) gives acid catalysis. The ratedetermining step should be the SN1 Co–O cleavage in a chelate ring to give a five coordinate intermediate.
Reaction Processes of Vanadium Bichloride Oxide and Vanadium Trichloride with Oxygen
Authors: Yajima Akimasa , Matsuzaki Ryoko , Saeki Yuzo 
Published: July 2006

Abstract
The products formed by the heating of VCl2O in an oxygen stream at various temperatures were examined by chemical and X-ray analysis. The reaction products between VCl3 and oxygen were examined in the same manner. The reaction process between VCl2O and oxygen may be represented as follows: VCl2O reacts with oxygen above ca. 170 °C to form V2O5 and VCl3O, 12VCl2O(s)+3O2(g)→2V2O5(s)+8VCl3O(g), and this reaction is accompanied by the reaction, 4VCl2O(s)+3O2(g)→2V2O5(s)+4Cl2(g). The reaction process between VCl3and oxygen may be represented as follows: VCl3 reacts with oxygen above ca. 100 °C to form VCl3O, 2VCl3(s)+O2(g)→2VCl3O(g), and this reaction is accompanied by the reaction, 2VCl3(s)+O2(g)→2VCl2O(s)+Cl2(g).
Catalytic Efficiency of Cationic Micellar Catalysts Bearing a Mercapto Group as the Reaction Center
Authors: Murakami Yukito , Nakano Akio , Matsumoto Kiyoshi , Iwamoto Kiyoshi 
Published: July 2006

Abstract
In order to clarify micro-environmental effects on the reactivity of mercapto groups in enzymes, cationic surfactants bearing a mercapto group, N-hexadecyl-Nα-(3-trimethylammoniopropionyl)-l-cysteinamide bromide (CM·Cys-1) and N-dodecyl-Nα-(6-trimethylammoniohexanoyl)-l-cysteinamide bromide (CM·Cys-2), were synthesized and their kinetic behavior investigated. The surfactants above their critical micelle concentrations markedly catalyzed the decomposition p-nitrophenyl hexanoate (PNPH) and acetate (PNPA), the concentrationrate profiles being found to be those for typical micelle-catalyzed reactions. The rate constants for the degradation of PNPH as catalyzed by CM·Cys-1 and -2 in the micellar phase are 0.482 and 0.197 s−1, respectively, in 9.8% (v/v)ethanol–1.0%(v/v)dioxane–1.0%(v/v)methanol-water at 30.0±0.1 °C, pH 8.65, and μ0.10 (KCl). The difference in catalytic activity can be attributed partly to the micro-environmental effect on the pKa value of the mercapto group lying at the reaction center. The rate constants for the thiolate anions (true reactive species) of CM·Cys-1 and -2 to react with PNPH were identical with each other irrespective of the nature of the surfactants. The electrostatic effect provided by the cationic charge in the Stern layer, which acts to reduce the pKa value of the reactive mercapto group, seems to play a more important role than the desolvation effect on the thiolate anion by the hydrophobic field.
Reaction of Diazo Ketones in the Presence of Metal Chelates. VII. 1,3-Dipolar Cycloaddition of 1-Methoxybenzo[c]pyrylium-4-olate with Acetylenic Dipolarophiles
Authors: Ibata Toshikazu , Jitsuhiro Kimiko 
Published: July 2006

Abstract
The Cu(acac)2 catalyzed decomposition of o-methoxycarbonyl-α-diazoacetophenone (3) in the presence of acetylenic dipolarophiles gave cycloadducts of the dipolarophiles with 1-methoxybenzo[c]pyrylium-4-olate generated by the intramolecular carbene-carbonyl reaction of the corresponding carbene. The direction of the cycloadditions of unsymmetrically substituted acetylenes has been determined on the basis of the NMR coupling pattern and chemical shift of the bridgehead methine protons of the adducts. Treatment of 3 with strong dipolarophiles such as dibenzoylacetylene or dimethyl acetylenedicarboxylate gave spiro pyrazoles by the direct cycloaddition of 3 and acetylenes followed by the elimination of methanol.