Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 59 , Issue 11
Showing 1-50 articles out of 72 articles from the selected issue
  • Osamu Ikeda, Toyosei Kojima, Hideo Tamura
    1986 Volume 59 Issue 11 Pages 3335-3340
    Published: 1986
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Electrocatalysis of the heat-treated (5,10,15,20-tetraphenylporphyrinato)manganese(III) halides (MnIII(TPP)X, X:F, Cl, Br, I) for the O2 reduction in an alkaline solution has been studied by rotating ring-disc electrode technique, and the result was correlated with properties of the heat-treated MnIII(TPP)X, such as magnetic moment and electrical resistivity. The axial ligand X showed noticeable effect on the catalytic activity. The catalytic activity estimated from the overpotential changed in the following order: F>Cl>Br>I. The catalytic activity for reducing oxygen to OH was low, but the same order of activity as the above applies. The order was interpreted by the σ-donating ability of halide ion X to dz2 orbital. The active site of the MnIII(TPP)X heat-treated at 700 °C for O2 reduction is ascribed to the metal ion, coordinated to slightly degraded or perfect N4 center, but not degradation products of the relevant compounds.
  • Yosuke Kataoka
    1986 Volume 59 Issue 11 Pages 3341-3346
    Published: 1986
    Released: June 27, 2006
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    Constant-temperature constant-pressure molecular dynamics simulations of a two-dimensional aqueous solution-like system are performed at many temperatures under a constant pressure. The total number of molecules in the system is 576, and the mole fraction of the solute is 0.5. The mutual diffusion coefficient, the kinetic diffusion coefficient, and the velocity correlation between different molecules are thus obtained. The reduced kinetic diffusion coefficient has a maximum at an intermediate temperature under a constant pressure. This feature is consistent with the temperature dependence of the mean-square-concentration fluctuations. The lifetime of the local structure is estimated from the cross-correlation function of displacement, which is computed from the time-averaged configurations, where the average period is several times longer than the velocity-autocorrelation time. The correlation length of the local concentration fluctuations is obtained and compared with the snapshots of the configurations at several temperatures. The dynamical properties are qualitatively in agreement with those of an alcohol–water mixture.
  • Masao Ichinose, Takashi Yasuoka, Shunmei Mitsuzawa, Tsunetaka Sasaki
    1986 Volume 59 Issue 11 Pages 3347-3349
    Published: 1986
    Released: June 27, 2006
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    An electrolytic removal of potassium and sodium sulfates from aqueous solutions was worked out by using an active-charcoal cathode and a platinum anode with a porous porcelain septum between them. Maximum removal of nearly 99% was attained for these salts. The mechanism of removal was confirmed to be based on the facts that potassium and sodium ions are entrapped and concentrated as hydroxides in the pores of the active-charcoal cathode while sulfate ions are removed from the solution and concentrated as sulfuric acid in the anode chamber.
  • Kenji Okuyama, Hitoshi Watanabe, Masatsugu Shimomura, Kiyoshi Hirabaya ...
    1986 Volume 59 Issue 11 Pages 3351-3356
    Published: 1986
    Released: June 27, 2006
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    Azobenzene-linked, single-chain ammonium amphiphile (C12AzoC5N+Br), C33H54N3O3Br, was crystallized from their solutions in water and ethanol. The crystals are triclinic with the space group P\bar1, Z=2, a=3.4243(6), b=0.8525(1), c=0.6073(1)nm, α=73.45(1), β=88.03(1), and γ=93.32(1)°. The structure was solved by the direct method and refined anisotropically by the block-diagonal least-squares procedure: R=0.06 for 2917 observed reflections (2θ<105°, Cu Kα, λ=0.154184 nm). The crystal structure consists of regularly stacking bimolecular layers in which C12AzoC5N+Br molecules incline about 30° to the layer surface. As expected from spectroscopic analyses, the azobenzene chromophore shows a head-to-tail (J-like) aggregation between adjacent molecules. The pronounced planarity of the azobenzene chromophore found in this crystal structure enables parallel stacking of phenyl groups in the J-like aggregation.
  • Kazunori Maruyama, Yoshié Tanizaki
    1986 Volume 59 Issue 11 Pages 3357-3361
    Published: 1986
    Released: June 27, 2006
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    Dichroic spectra of polyenes –(CH=CH)n– produced in heat-treated poly(vinyl alcohol) [PVA] film were determined for two cases; stretch (at 85 °C) after heat (120 °C), (Δ,S), and heat after stretch, (S,Δ). The dichroic ratios Rdn of component polyenes (n=2–6) were estimated by means of simulation. In both cases (Δ,S) and (S,Δ), the relation of Rdn vs. Rs (stretch ratio) kept the theoretical equation of the dichroism analysis. The relative angles among the transition moments μn (n=2–6) were in accordance with those obtained by drawings of trans-polyenes. The idea of an azimuth vector in the stretched PVA substrate was justified. The relation of Rdn(Δ,S)>Rdn(S,Δ) was always observed at any Rs. This was explained by the thermal orientation-relaxation of polymer chains.
  • Kunio Esumi, Kazuaki Miyata, Fumio Waki, Kenjiro Meguro
    1986 Volume 59 Issue 11 Pages 3363-3366
    Published: 1986
    Released: June 27, 2006
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    Adsorption of tetrachloro-p-benzoquinone(chloranil) from basic and acidic solvents on metal oxides, such as alumina and titania was carried out to understand the acid-base interaction at the interface. The amount of chloranil adsorbed decreases with an increase of acid-base interaction between the basic solvent and chloranil and also decreases with an increase of acid-base interaction between the acidic solvent and electron donor sites of the metal oxides for both metal oxides. Furthermore, the change in concentration of chloranil radicals formed on their metal oxides by the adsorption is correlated with the acid-base interaction at the interfaces.
  • Jun Shimizu, Kengo Imamura, Takashi Nogami, Hiroshi Mikawa
    1986 Volume 59 Issue 11 Pages 3367-3373
    Published: 1986
    Released: June 27, 2006
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    Phase transitions of unsymmetric bis(quaternary alkyl bromide) salts of 1,4-diazabicyclo[2.2.2]octane (DABCO)(C10–DABCO–Cn–Br2, 11≤n≤22) were studied on the basis of measurements of differential scanning calorimetries, infrared absorption spectroscopy, and bromide-anion conductivities. The DSC measurements showed two transition temperatures (Tc1 and Tc2, Tc1>Tc2); this exhibits the existence of the metastable phase for the DABCO salts (C10–DABCO–Cn-Br2, 12≤n≤22). The metastable phase was converted to the stable phase within several days except for C10–DABCO–Cn–Br2 (n=12, 22). The temperature dependence of the infrared absorption spectra revealed that the band progressions due to two different alkyl chains disappeared at Tc1 and appeared again at Tc2. This shows that the trans-zigzag conformation of the alkyl chains in the low temperature phase is destroyed by the conformational change above Tc1 and then recovered again below Tc2. Abrupt increases in the bromide-anion conductivities by 100–1380 times were observed at around Tc2 for the samples annealed beforehand above Tc1. However, the virgin samples showed much broader increases in the conductivities below Tc1; no conductivity jump was observed. The conductivity increase was caused by the conformational change in the alkyl groups. The concomitant formations of the voids facilitate the bromide-anion transport.
  • A. K. Srivastava, Isao Kojima, Eizo Miyazaki
    1986 Volume 59 Issue 11 Pages 3375-3382
    Published: 1986
    Released: June 27, 2006
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    Complete neglect of differential overlap (CNDO) molecular orbital calculations using the method of Anno and Sakai for the evaluation of the valence orbital ionization potential (VOIP) were performed with the aim of studying the oxidation of carbon monoxide on nickel clusters. A cluster surface was assumed to be preadsorbed with oxygen and the variation of various bond energies with the approach of a carbon monoxide molecule was studied for different models. Various possibilities for the reaction path are discussed in the light of the theoretical findings and it is suggested that at a low coverage of oxygen the reaction may follow a Langmuir–Hinshelwood path, whereas at a high coverage, an Eley–Rideal path might be more probable.
  • Hazime Saitô, Ryoko Tabeta, Akio Kuzuhara, Tetsuo Asakura
    1986 Volume 59 Issue 11 Pages 3383-3387
    Published: 1986
    Released: June 27, 2006
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    An attempt was made to prepare [Ser-3,3-2H2]- and [Ala-3,3,3-2H3]-fibroins by feeding respective amino acids DL-[3,3-2H2]-serine (Ser) and [3,3,3-2H3]-alanine (Ala), respectively, to silkworms, Bombyx mori and Philosamia cynthia ricini together with daily artificial diet. We recorded 2H powder-pattern NMR spectra of [Ser-3,3-2H2]- and [Ala-3,3,3-2H3]-cocoons and fibroins (10–20% deuteration) by means of the quadrupole echo method. It was found that separation of the 2H quadrupole splittings is 125 and 39 kHz, respectively, for [Ser-3,3-2H2]- and [Ala-3,3,3-2H3]-cocoons and fibroins, respectively. Accordingly, it was concluded that side-cain reorientation of Ser residue is virtually frozen irrespective of differences in conformations of silk I and silk II, suggesting that the hydroxyl groups in these cases might be hydrogen-bonded to C=O or NH groups in intra or interchain. On the other hand, side-chain methyl group of Ala residue in [Ala-3,3,3-2H3]-fibroin turned out to undergo rapid three-fold rotation about the Cα–Cβ axis, as viewed from data of the quadrupole splittings.
  • Fujio Tanaka, Yoshiko Kawasaki, Shigeru Yamashita
    1986 Volume 59 Issue 11 Pages 3389-3392
    Published: 1986
    Released: June 27, 2006
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    The luminescence lifetime for Eu2(SO4)3 and EuCl3 in H2O and D2O has been measured at 0.01 and 0.001 mol dm−3 of Eu3+ and at various temperatures from 5 to 45 °C. The average number of water molecules coordinated to Eu3+ ion, q, is evaluated from the difference of the luminescence decay constants in the H2O and D2O solutions. By using the q value of 8.3 for aquaeuropium(III) ion in EuCl3 solutions, q values for Eu2(SO4)3 solutions were determined as a function of concentration and temperature. The average number of water molecules released from the primary hydration sphere by the inner-sphere complexation between Eu3+ and SO42− ions is given as Δq=8.3–q, and Δq value increases with concentration and temperature. From the values of Δq and the known equilibrium constants on the overall complexation, it is revealed that for both the unis(sulfato) and bis(sulfato) complexation the ratio of inner-sphere complex to outer-sphere complex increases with temperature and that about one water molecule is released from the inner hydration sphere surrounding Eu3+ ion on the formation of an inner-sphere unis(sulfato) complex. The coordination state of the unis(sulfato) complex and the thermodynamic quantities for the equilibrium between outer- and inner-sphere complexes are discussed.
  • Kiyofumi Murakami, Katsumi Mizuguchi, Yukio Kubota, Yasuo Fujisaki
    1986 Volume 59 Issue 11 Pages 3393-3397
    Published: 1986
    Released: June 27, 2006
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    The thermodynamics and kinetics of the dimerization of Acridine Orange (AO, 3,6-bis(dimethylamino)acridinium chloride) and its 10-alkyl derivatives in 0.1 M NaCl solution have been studied by spectrophotometry and temperature-jump method. Dimerization constants, which were determined spectrophotometrically, become large with an increase in the length of the introduced alkyl chain; this behavior is the same as that in water and a dilute HCl solution. The association and dissociation rate constants determined from the temperature-jump measurements also depend on the length of the alkyl chain. Especially, the rate constants for methyl–AO are unexpectedly small. Both the effect of added salt on the thermodynamic parameters and the kinetic results are discussed in view of the structure of hydration water surrounding dye molecules. 1H NMR data for AO and methyl–AO suggest that the planes of two component molecules in a dimer are parallel to each other. This result is consistent with the spectrophotometric and kinetic data.
  • Kiyofumi Murakami, Yukio Kubota, Yasuo Fujisaki, Takayuki Sano
    1986 Volume 59 Issue 11 Pages 3399-3403
    Published: 1986
    Released: June 27, 2006
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    The complex formation between pyridoxal 5′-phosphate (PLP) and bovine serum albumin at pH=7.0 and 25 °C was characterized by four relaxation processes. The dependence of the reciprocal relaxation times upon reactant concentrations was found to be consistent with a mechanism in which a rapid bimolecular binding step is followed by three sequential isomerization steps. The eight rate constants for this mechanism were determined and then combined to calculate an overall equilibrium constant which is in agreement with the literature value. Absorption spectra of the complexes formed by the two faster steps were determined from absorbance changes associated with them; the spectrum corresponding to the first complex has two bands at 330 nm and 360 nm and an additional 410 nm band, while the spectrum corresponding to the second complex has a large single band at 375 nm. Comparing these spectra with those reported for other PLP-enzyme systems, we speculate that four steps in the proposed mechanism may correspond to the rapid formation of a carbinolamine, which is in very rapid equilibrium with a Schiff base form, followed by the deprotonation of the ring nitrogen, the formation of an ionic hydrogen-bonded Schiff base, and the final formation of a nonionic hydrogen-bonded Schiff base.
  • Osamu Sekiguchi, Nobuhiro Ohta, Hiroaki Baba
    1986 Volume 59 Issue 11 Pages 3405-3415
    Published: 1986
    Released: June 27, 2006
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    Emission characteristics of pyrimidine vapor which were measured after excitation into various S1 vibronic levels with relatively low excess vibrational energies (ΔE) below 2650 cm−1 were found to depend markedly upon ΔE. The emission from a vibronic level with ΔE<1000 cm−1 (e.g., 6a1 or 11) is sharp and attributable to the fluorescence from the initially prepared vibronic level (IPL), and that from a vibronic level with ΔE>1000 cm−1 (e.g., 121, 6a2, or 122) involves broad fluorescence besides the IPL fluorescence. At low pressure, the broad fluorescence consists of fast and slow components with lifetimes comparable to those for the corresponding components of the IPL fluorescence. The broad fluorescence exhibits another slow component which is characterized by a less tendency to undergo collisional quenching. The quantum yield of the slow component of the IPL fluorescence clearly depends upon molecular rotation, whereas that of the broad fluorescence appears to show little or no rotational-level dependence. On the basis of these observations, the broad fluorescence is assigned to the one originating from S1 vibronic levels that can be reached directly from the IPL through intramolecular vibrational redistribution (IVR) or indirectly via triplet levels. There exists no evidence to show that the IVR is affected by molecular rotation.
  • Hiroshi Sakai, Manabu Mizota, Yutaka Maeda
    1986 Volume 59 Issue 11 Pages 3417-3421
    Published: 1986
    Released: June 27, 2006
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    The Mössbauer effect of 129I has been applied to investigate tetrathiafulvalene–iodine (TTF–In) charge-transfer salts at 16 K. The electrically conductive TTF–I0.71 salt shows a broad single-line with the isomer shift of −0.36 mm s−1, suggesting that the iodine atoms on the average are not completely ionic (I−1.0) but are negatively charged by about 0.9 (I−0.9) in the low temperature phase. This is due to the weak interactions of the iodine atoms with the sulfur atoms of the TTF molecules. This fact is consistent with the crystallographic data and the electron spin resonance spectra of the salt. This salt is recognized as a partially oxidized mixed-valence compound. The spectrum of the TTF–I3 salt consists of two sets of quadrupole octets, corresponding to the central and terminal iodine atoms of the slightly distorted I3 ion. The charge density localized on each iodine atom of the I3 ion is close to that of the isolated I3 ion. That is, the salt is regarded as a simple ionic compound, for which a high electrical conductivity can not be expected. It is confirmed that a small amount of the TTF–I2 salt coexists in the TTF–I0.71 phase obtained from the solution of excess TTF and iodine. In the salt the iodine atoms exist as polyiodides consisting predominantly of I3 units.
  • Takeo Ohsaka, Kazuhiko Hirabayashi, Noboru Oyama
    1986 Volume 59 Issue 11 Pages 3423-3429
    Published: 1986
    Released: June 27, 2006
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    The kinetic study of the mechanism for the reaction of the initial stages of the electropolymerization of 1-pyrenamine (PA) in an acetonitrile solution was carried out by cyclic voltammetry (CV) and double potential-step chronoamperometry (DPSCA). The experiments were conducted at various time windows (i.e., at various scan rates of CV and various potential-step widths of DPSCA) and under the conditions of the presence or absence of the basic or acidic additives (pyridine, 2,6-lutidine, trifluoroacetic acid). As a result, it was found that the mechanism of the reaction of the initial stages of the electropolymerization of PA is an “ECE” mechanism, and that the chemical reaction interposed between successive electron transfers is considered as the radical–radical coupling reaction rather than the radical–parent monomer coupling reaction. The second-order rate constant for the radical–radical coupling reaction was estimated to be (1.0±0.8)×105 M−1 s−1 (1 M=1 mol dm−3). The cyclic voltammetric responses for the oxidation of PA were varied by the presence or absence of the basic or acidic additives. This can be explained considering the basicity of the additives and their influences in the deprotonation reactions following the heterogeneous electron transfer step.
  • Nobuyuki Fujii, Syuji Uchida, Hisaaki Sato, Shiro Fujimoto, Hajime Miy ...
    1986 Volume 59 Issue 11 Pages 3431-3437
    Published: 1986
    Released: June 27, 2006
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    The high-temperature reaction of NH3 with N2O in shock waves was investigated by measuring ultaviolet absoption of NH3 and OH, and infrared emission of N2O, in the temperature range of 1700–2300 K on the mixture of NH3–N2O diluted with large amount of argon. A comparison of the observed decays of NH3 and N2O and the formation of OH with those obtained by computer simulation behind the incident shock wave was carried out. From the comparison, the rate constants of the following elementary reactions were determined: NH3+O→NH2+OH[k4=1012.5exp(−25.5 kJ⁄RT) cm3 mol−1 s−1]; NH3+OH→NH2+H2O[k5=1012.5exp(−8.4 kJ⁄RT) cm3 mol−1 s−1].
  • Masashi Tanaka
    1986 Volume 59 Issue 11 Pages 3439-3442
    Published: 1986
    Released: June 27, 2006
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    The polarized reflection spectra of the crystal of (DBTTF)4·(BF4)2·EtOH complex were measured and the optical parameters were determined by the simulation of the observed reflection spectra. The theoretical analysis of the observed spectra shows that the electronic structure of DBTTF cation molecules is typical of the island type configuration. The 4000 and 11500 cm−1 bands polarized parallel to the stacking axis were assigned to the CT2 and CT1 bands, and the parameters U and t of the Hubbard Hamiltonian were estimated to be (U=8950 cm−1 and t=1250 cm−1.
  • Shuichi Hamada, Shin Niizeki, Yoshiyuki Kudo
    1986 Volume 59 Issue 11 Pages 3443-3450
    Published: 1986
    Released: June 27, 2006
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    Monodispersed α-iron(III) oxide (hematite) particles were prepared by aging iron(III) chloride solutions in the presence of glycine at elevated temperatures, 98–100 °C. An aqueous solution of glycinatoiron (III) complex directly gave monodispersed double spheres of hematite, ≈4 μm in size, under the specified conditions, for example, 2.0×10−2 mol dm−3 FeCl3, 0.60 mol dm−3 glycine, and 0.46 mol dm−3 HCl for 96 h. The hematite particles grew up through the polynuclear layers mechanism. By the forced hydrolysis in 2-propanol/water mixed solution of 30% by volume, monodispersed cuboidal hematite particles, 0.06–0.43 μm in size, were also obtained through the conversion of β-iron(III) hydroxide oxide previously deposited. The nucleation rate was markedly affected by acidity at the latter case. The formation processes of these monodispersed hematite particles are discussed.
  • Koji Kano, Masaru Yanagimoto, Shizunobu Hashimoto
    1986 Volume 59 Issue 11 Pages 3451-3457
    Published: 1986
    Released: June 27, 2006
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    The rate constants for photochemical processes of pyrene in perfluorohexane (PFH) and hexane containing N,N-dimethylaniline (DMA) have been determined by analyzing the rise and decay curves of the pyrene–DMA exciplex to study the interaction between electronically polar exciplex and an extremely nonpolar solvent, PFH. In PFH, the dissociation of the exciplex to the original pyrene in the excited singlet state and DMA was decelerated and the radiationless deactivation of the exciplex to the ground states was accelerated. In the case of the naphthalene–triethylamine exciplex system, the radiationless deactivation of the exciplex was also much faster in PFH than in hexane. These results suggest charge-transfer interactions between the polar exciplexes and PFH. The negative charges of the exciplexes may transfer to the strongly electronegative fluorine atom(s) of PFH. The deceleration of the back reaction and the acceleration of the radiationless deactivation seem to lead the efficient fluorescence quenching of pyrene and naphthalene by amines in PFH.
  • Masato Tazaki, Takashi Hayashita, Yasumitsu Fujino, Makoto Takagi
    1986 Volume 59 Issue 11 Pages 3459-3464
    Published: 1986
    Released: June 27, 2006
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    The isotachophoretic behavior of aromatic nucleus-containing quaternary ammonium ions was studied in the presence of a neutral ligand, α-cyclodextrin. Due to the interaction of cyclodextrin with the hydrophobic aromatic nucleus, isomeric ammonium ions containing, e.g., an o-, m-, or p-disubstituted benzene ring, were satisfactorily separated. In the absence of cyclodextrin, the separation of the isomers was poor. A theoretical approach was also used in order to evaluate the binding equilibrium constant (K) between the analyte ion and α-cyclodextrin through an isotachophoretic measurement. The binding constants (logK) with (o-, m-, and p-methylbenzyl)trimethylammonium ions were found to be 0.8, 1.1, and 1.6, respectively.
  • Yoshitsugu Hasegawa, Midori Kamikawaji, Kaname Sasaki
    1986 Volume 59 Issue 11 Pages 3465-3468
    Published: 1986
    Released: June 27, 2006
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    Copper(II)–dithiooxamide (rubeanic acid) complex was synthesized in the interlayer region of zirconium phosphate. The product, called ZP–CuLra, was chracterized by chemical analysis, thermal analysis, infrared spectroscopy, and X-ray diffractometry. The chemical composition of ZP–CuLra was represented as ZrCu(H2NCS)2(PO4)2·H2O or ZrCu(HNCS)2(HPO4)2·H2O. The interlayer distance of ZP–CuLra was found to be 9.0 Å. By analogy with Cu(II)–rubeanic acid complex prepared in a solution, a structural model of ZP–CuLra was proposed.
  • Hitoshi Watarai, Manabu Takahashi, Kiyoji Shibata
    1986 Volume 59 Issue 11 Pages 3469-3473
    Published: 1986
    Released: June 27, 2006
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    The interfacial adsorption of (E)-2′-hydroxy-5′-nonylacetophenone oxime and its role in the extraction kinetics of the nickel(II) ion with the oxime were investigated in heptane/aqueous phase systems by means of a high-speed stirring apparatus. The interfacial oxime concentration was correlated to the organic phase concentration, obeying the Langmuir isotherm. The interfacial activity of the oxime was also measured by means of interfacial tension measurements. The initial extraction rate of nickel(II) ion was linearly proportional to the interfacial concentration of the oxime (rather than to the bulk-phase concentration), to the nickel-ion concentration, and inversely to the hydrogen-ion concentration. These results supported the mechanism that the rate-determining step in the extraction is the 1:1 complex formation at the interface.
  • Katsuhiko Miyoshi, Shinji Izumoto, Hayami Yoneda
    1986 Volume 59 Issue 11 Pages 3475-3482
    Published: 1986
    Released: June 27, 2006
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    An association model has been proposed which accounts for how bis(μ-d-tartrato)-diantimonate(III) anion, [Sb2(d-tart)2]2− ion recognizes the chirality of [Co(en)3]3+ (en=ethylenediamine) and some related cation complexes in solution. In this model, two oxygen atoms of the chiral anion, i.e., the carboxylic oxygen atom (coordinated to the Sb atom) of one d-tartrate moiety and the alcoholic oxygen atom (coordinated to the same Sb atom) of the other d-tartrate moiety, are hydrogen-bonded to the two amine protons in [Co(en)3]3+ which are directed along either the C3 or C2 axis. When these hydrogen bonds are formed along the C3 axis (C3 association), [Sb2(d-tart)2]2− ion forms a more favorable ion pair with Λ-[Co(en)3]3+, whereas it does with Δ-[Co(en)3]3+ if the two amine protons directed along the C2 axis are utilized for hydrogen bonding to it (C2 association). This model is successfully applied to the interpretation of chromatographic behavior of some [Co(N)6]3+-type complexes as well as of their related complexes with amine or phosphine ligands.
  • Hidenari Inoue, Hiroko Nakajima, Takeshi Takahashi, Hiroshi Uchida, Ts ...
    1986 Volume 59 Issue 11 Pages 3483-3488
    Published: 1986
    Released: June 27, 2006
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    A new type of the mixed ligand complex [Fe(bpy)(phen)(NCS)2] (bpy=2,2′-bipyridine and phen=1,10-phenanthroline) has been prepared by two different methods. The influence of the mixed ligand coordination of bpy and phen to a central iron(II) ion is studied by measurements of the temperature variation of magnetic moments and Mössbauer parameters. It has been demonstrated that the mixed coordination tends to make the 5T2(high-spin) \ ightleftharpoons 1A1(low-spin) transition more gradual. The spin-crossover transition temperature depends on the electronic property as well as the structure of the ligand coordinated to the central iron(II) ion.
  • Takashi Ito, Akihiko Takahashi, Shigeyoshi Tamura
    1986 Volume 59 Issue 11 Pages 3489-3494
    Published: 1986
    Released: June 27, 2006
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    Cationic carboxylatodihydridomolybdenum(IV) complexes, [MoH2(O2CR)(dppe)2]BPh4 (R=CH3, C2H5, CH2=CH, and CH2=C(CH3); dppe=Ph2PCH2CH2PPh2), were prepared by treating [MoH4(dppe)2] with RCOOH followed by anion exchange with NaBPh4, and characterized spectroscopically. A possible pathway of the reaction is discussed on the basis of the experiment using CH3COOD. Light irradiation of the EtOH solution of the cationic acetato complex in the presence and absence of CO afforded the known cis-[Mo(CO)2(dppe)2] and the neutral hydridoacetato complex, [MoH(O2CCH3)(dppe)2], respectively.
  • Hisashi Kinoshita, Akira Ouchi
    1986 Volume 59 Issue 11 Pages 3495-3499
    Published: 1986
    Released: June 27, 2006
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    The title complex was synthesized and its crystal and molecular structure were determined by the single-crystal X-ray diffraction technique. The crystal is orthorhombic with a space group P21nb, a=14.953(4), b=15.955(4), c=7.6838(9) Å. The crystal was solvent by means of the heavy-atom method and the final R value was 0.059. The mercury atom is in the tetrahedral geometry, coordinated with four sulfur atoms of the thiocyanate (SCN) ions, and the cobalt atoms is in the octahedral geometry, coordinated with four nitrogen atoms of SCN ion and two oxygen atoms of N-methylformamide which occupy the cis positions. Each pair of different kinds of metal atoms is bridged by an SCN ion and are in a three-dimensional network. Twenty-four membered rings of Co3Hg3(SCN)6, where the metal atoms are arranged hexagonally in a chair-form, are condensed two-dimensionally approximately parallel to the (100) plane. All mercury atoms on one plane are bridged by SCN ions to the cobalt atoms of the polymeric plane next to the [100] direction, while the cobalt atoms are linked by SCN ions to the mercury atoms on the next plane of the opposite side. The mfa ligands take their positions in vacancy of the network.
  • Takeshi Sakurai, Akitsugu Nakahara
    1986 Volume 59 Issue 11 Pages 3501-3504
    Published: 1986
    Released: June 27, 2006
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    The two type I copper sites of human and bovine ceruloplasmin (CP) were indirectly modified through the binding of N3 to types II and III copper ions. Based on the fact that the activities of CP’s modified with N3 were 85 and 47% for human and bovine CP, respectively, it was disclosed that the electronic and steric states of the “fast” type I Cu or “CuA” which is coupled with the types II and III copper ions was changed reversibly, whilst the “slow” type I Cu or “CuB” which is not coupled with the types II and III copper ions was changed to a type II copper ion and/or irreversibly reduced. On the other hand, the reaction of a limited amount of L-cysteine with CP gave the absorption and electron paramagnetic resonance spectra of CP whose CuB was selectively reduced. The treatment of this CP with 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline-4′,4″-disulfonate did not result in the selective removal of CuB.
  • Kiyohiko Nakajima, Masaaki Kojima, Junnosuke Fujita
    1986 Volume 59 Issue 11 Pages 3505-3510
    Published: 1986
    Released: June 27, 2006
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    The selenide (selenoether) complexes, [Co(β-dik)2(CH3SeCH2CH2NH2)]+ (β-dik: acac=2,4-pentanedionate, Clacac=3-chloro-2,4-pentanedionate, Meacac=3-methyl-2,4-pentanedionate, and dbme=1,3-diphenyl-1,3-propanedionate) were prepared and separated into two racemic pairs of the diastereomers (Δ(R)Λ(S) and Δ(S)Λ(R) isomers). The complexes in solution epimerize by inversion at the selenium atom, and the rates were followed by high-performance liquid chromatography in the temperature range of 30.3–55.0 °C in 0.05 mol dm−3 Na2SO4 (acac, Clacac, and Meacac complexes) or in methanol (dbme complex). The ΔG25°C\ eweq values for inversion of [Co(β-dik)2(CH3SeCH2CH2NH2)]+ decrease in the order β-dik=Clacac(108)>acac(106)>dbme(104)>Meacac(100 kJ mol−1), and the decrease in ΔG25°C\ eweq comes mainly from a decrease in ΔH\ eweq. The effect of substituents is electronic and the Hammett relationship was found to hold for the inversion rates of the acac, Clacac, and Meacac complexes.
  • Yosuke Koizumi, Hisanori Horita, Tetsuo Otsubo, Nobutami Kasai, Soichi ...
    1986 Volume 59 Issue 11 Pages 3511-3514
    Published: 1986
    Released: June 27, 2006
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    The molecular structure of the title compound has been determined by means of X-ray diffraction. C26H25Br, M 417.4, orthorhombic, space group P212121, a=12.713(1), b=14.998(1), c=10.156(1) Å, V=1936.3(1) Å3, Dm=1.43 g cm−3, Dc=1.432 g cm−3 for Z=4.
  • Takeshi Negoro, Yoshitsugu Ikeda
    1986 Volume 59 Issue 11 Pages 3515-3518
    Published: 1986
    Released: June 27, 2006
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    The bromochlorination of phenyl- and alkyl-substituted acetylenes with tetrabutylammonium dichlorobromate(1−) (1) in dichloromethane was found to be anti-stereospecific and nonregiospecific (regiospecific in the case of phenylacetylene). Whereas the addition of molecular bromine chloride (2) to phenyl-substituted acetylenes was found to give nonstereospecific and regiospecific adducts, the reaction of alkyl-substituted acetylenes gave anti-stereospecific and nonregiospecific adducts. These results suggest that the addition of 1 involves an attack of chloride ion to a three-centered π-complex in the product-forming stage, and that the addition of 2 to phenyl-substituted acetylenes involves a vinyl cation intermediate (but a bridged bromonium ion intermediate in the case of alkyl-substituted acetylenes).
  • Takeshi Negoro, Yoshitsugu Ikeda
    1986 Volume 59 Issue 11 Pages 3519-3522
    Published: 1986
    Released: June 27, 2006
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    The bromochlorination of styrene derivatives with tetrabutylammonium dichlorobromate(1−) (1) in such protic solvents as acetic acid and methanol gives the corresponding bromo chloro adducts along with substantial amounts of solvent-incorporated products in a regiospecific manner (regioselective in the case of 3-nitro- or 2-chlorostyrenes). The reaction of 1-phenylpropenes with 1 gives nonstereospecific but regiospecific adducts. These results suggest that the addition of 1 to styrene derivatives in protic solvents involves an attack of chloride ion or solvent molecule to a bromonium ion intermediate.
  • Osamu Sakanaka, Takashi Ohmori, Shuji Kozaki, Tetsuo Suami
    1986 Volume 59 Issue 11 Pages 3523-3528
    Published: 1986
    Released: June 27, 2006
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    A conversion of 5-acetamido-5-deoxy-1,2:7,8-di-o-isopropylidene-3-o-methylthiomethyl-β-L-erythro-D-allooctofuranose-(1,4) and -L-talooctofuranose-(1,4) to 5-amino-3,7-anhydro-5-deoxyoctofuranose-(1,4) derivatives has been investigated as a preliminary study for a synthesis of the octose moiety of ezomycins.
  • Makoto Karatsu, Hiroko Suezawa, Kazuhisa Abe, Minoru Hirota, Motohiro ...
    1986 Volume 59 Issue 11 Pages 3529-3534
    Published: 1986
    Released: June 27, 2006
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    Isopropyl-2-d 1-(p-X-phenyl)ethyl ketones (where, X=H, NO2, Br, Cl, C2H5, CH3, and NH2) were shown to have two absorption bands in the C–D stretching region. The absorption band at the higher frequency (ca. 2177 cm−1) is assigned to the C–D···π approached conformer, and the high frequency shift is ascribed to the effect of steric compression. Weak C–D···π hydrogen bond was shown to occur by the measurement of the substituent effect on the formation constant and the relative enthalpy of the C–D···π approached conformer.
  • Munehiro Nakatani, Yuji Fukunaga, Hiroyuki Haraguchi, Makoto Taniguchi ...
    1986 Volume 59 Issue 11 Pages 3535-3539
    Published: 1986
    Released: June 27, 2006
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    Eight terminal acetylenic fatty acids from 5-hexynoic to 12-tridecynoic acids and their methyl, ethyl, and isopropyl esters were synthesized via o-nitrophenyl selenides. These acids and esters all showed inhibitory effect on lettuce seed germination and seedling growth. The effect was dependent on the number of carbon atoms in acetylenic chain. 8-Nonynoic acid showed potent activity, and its methyl ester was the most effective among the test compounds. In addition, the acids showed antifungal activity which increased as the number of carbon atoms increased.
  • Toshiro Sakaki, Shin Yoshimura, Takahiko Tsuyuki, Takeyoshi Takahashi, ...
    1986 Volume 59 Issue 11 Pages 3541-3546
    Published: 1986
    Released: June 27, 2006
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    Four new bitter quassinoid glycosides, yadanziosides K, M, N, and O were isolated from Brucea javanica (L.) MERR and their structures were determined by spectral measurement and chemical means. The aglycone of yadanzioside O was found to exhibit a significant antitumor activity against the murine P388 lymphocytic leukemia and this aglycone could be prepared from brusatol.
  • Mitsuaki Narita, Shizuko Isokawa, Masamitsu Doi, Ryuhei Wakita
    1986 Volume 59 Issue 11 Pages 3547-3552
    Published: 1986
    Released: June 27, 2006
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    In order to investigate the ability of the Pro residue to promote helical folding in oligopeptides, the IR spectroscopic conformational study of the oligo(Leu)s containing the Pro residue was performed in dichloromethane. Their IR difference spectra suggested the occurrence of successive-intramolecular hydrogen bonds just like incipient α-helical structures formed by one, two, three, and so forth ii–4 hydrogenbonding patterns, alluding to the ability of the Pro residue to promote helical folding in the peptides. However, the intensities of hydrogen-bonded absorption bands in the amide A region of each peptide strongly suggested that conformations of the peptides investigated were also contributed by other intramolecularly hydrogen-bonded folded structures, which had lower absorption coefficients. The initiation mechanism of successive-intramolecular hydrogen bonding in the peptides is apparently attributed to the disturbance of the β-sheet formation by the rotation of the tertiary peptide bond plane (Leu–Pro), that is, the restriction of the values of the backbone dihedral angles φ and ψ of the Pro residue due to the low flexibility of the pyrrolidine ring.
  • Mitsuaki Narita, Masamitsu Doi, Koji Kudo, Yusuke Terauchi
    1986 Volume 59 Issue 11 Pages 3553-3557
    Published: 1986
    Released: June 27, 2006
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    IR spectroscopic conformational analyses of Boc–Glyn–OBzl (n=3–7) and Boc–(β-Ala)n–OBzl (n=3–8) were performed in the solid state, suggesting the occurrence of the β-sheet structure in the higher oligomers (n=5–8). Solubility data indicate that insolubilities of Boc–Glyn–OBzl and Boc–(β-Ala)n–OBzl in high-polar solvents begin at hexa- and heptapeptide levels, respectively. Insolubility of protected homooligopeptides of Gly and β-Ala was estimated to be caused by β-sheet aggregation. The high potential for the β-sheet formation of Boc–Glyn–OBzl and Boc–(β-Ala)n–OBzl (n≥5) could clearly be attributed to the great freedom of the peptide backbone dihedral angles of each of the Gly and β-Ala residues in the β-sheet structure. The implications of a replacement of a few Gly residues with β-Ala residues in surface regions of proteins are also discussed.
  • Michiyo Suzuki, Yoshikazu Kimura, Shiro Terashima
    1986 Volume 59 Issue 11 Pages 3559-3572
    Published: 1986
    Released: June 27, 2006
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    The bromolactonization of the optically active acetals derived from 2-acetyl-5,8-dimethoxy-3,4-dihydronaphthalene and (R,R)-N,N:N′,N′-tetraalkyltartaramide was found to proceed highly diastereoselectively, giving mixtures of the seven-membered bromo lactones and the bromohydrins. The predominantly produced bromo lactones could be effectively converted to (R)-2-acetyl-5,8-dimethoxy-1,2,3,4-tetrahydro-2-naphthol, the AB ring synthon of optically active 11-hydroxyanthracyclinones, >95% ee, in one pot reaction. Application of the explored synthetic scheme to 2-acetyl-5,12-dimethoxy- and 2-acetyl-5-methoxy-3,4-dihydro-6,11-naphthacenedione similarly gave (R)-2-acetyl-2,5,12-trihydroxy- and (R)-2-acetyl-2,5-dihydroxy-1,2,3,4-tetrahydro-6,11-naphthacenedione, the advanced key synthetic intermediates of optically active 4-demethoxy- and 11-deoxy-4-demethoxyanthracyclinones, 94% ee and >99% ee, respectively, by way of mixtures of the seven- and six-membered bromo lactones.
  • Chung-gi Shin, Yasuchika Yonezawa, Masahiro Ikeda
    1986 Volume 59 Issue 11 Pages 3573-3579
    Published: 1986
    Released: June 27, 2006
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    The one-pot syntheses of N-protected Δ1- and Δ2-dehydrodipeptide esters by the coupling of N-carboxy α-dehydroamino acid anhydride (ΔNCA) with several kinds of C- or N-protected L-α-amino acids are described. In addition, it was found that a similar coupling of ΔNCA with both C- and N-protected α-amino acids also took place to give Δ2-dehydrotripeptide derivatives, involving eight kinds of important C-terminal segments of antrimycins and cirratiomycins. The configurational confirmation of the α-dehydroisoleucine residue of the antibiotics is also discussed.
  • Daiyo Terunuma, Masato Kato, Masanao Kamei, Hidekatsu Uchida, Satoshi ...
    1986 Volume 59 Issue 11 Pages 3581-3587
    Published: 1986
    Released: June 27, 2006
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    New optically active organosilicon compounds such as (benzylmethylphenylsilyl)acetic acid (1) and (ethylmethylphenylsilyl)acetic acid (2) were synthesized. Application of these acids as the optical purity determining agents for chiral amines and alcohols were successfully carried out. In addition, it was also revealed that optically active (benzylmethylphenylsilyl)methylamine (3) and [benzylmethyl(o-tolyl)silyl]methylamine (4) are able to be used as the optical purity determining agents for chiral carboxylic acids.
  • Takeo Akiyama, Yukihiko Kawaharada, Akira Kondo, Masatsugu Kajitani, A ...
    1986 Volume 59 Issue 11 Pages 3589-3596
    Published: 1986
    Released: June 27, 2006
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    1,4- and 1,3-Diferrocenylbenzenes (1a and 1b), 1,2,4- and 1,3,5-triferrocenylbenzenes (1c and 1d) can act as photocatalysts for photochemical hydrogen evolution from methanol in the 1–methyl viologen MV2+–triethanolamine-colloidal Pt-catalyst system under the irradiation with visible light. The order of the photocatalytic activities of 1 is 1d>1c>1a>1b. The catalytic activities of 1 can be correlated to the E1⁄2 values. 1 acts as a photocatalyst in the wavelength region of λ>440 nm, whereas it acts as a quencher for the formation of MV\underset.+ in the wavelength region of λ<440 nm. The highest quantum yield of the formation of MV\underset.+ catalyzed by 1(1d: QMV\underset.+=0.028, at 480 nm) was obtained in the wavelength region where the intensity of the solar light is the largest.
  • Gaku Yamamoto, Michinori Oki
    1986 Volume 59 Issue 11 Pages 3597-3603
    Published: 1986
    Released: June 27, 2006
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    Five singly peri-substituted derivatives of 9-(3,5-dimethylphenoxy)triptycene with F, OCH3, CH3, Br, and C(CH3)3 as the peri-substituent were synthesized and their dynamic NMR behavior was studied. In any of the compounds, two m-methyl groups in the phenoxyl moiety were anisochronous at low temperatures and the signals coalesced into a single peak on raising the temperature. Lineshape analysis afforded the energy barriers to the rate process ranging from 10.1 kcal mol−1 (1 calth=4.184 J) for the F compound to 17.6 kcal mol−1 for the C(CH3)3 one. Molecular mechanics calculations (MM2) were performed on closely related model compounds to obtain the relative steric energies of the ground states and the possible transition states. The results from the dynamic NMR and the molecular mechanics studies suggest the following: When the peri-substituent is small (F and OCH3), the complete gear rotational circuit with the passing of the aryl group over the peri-substituent as the rate-determining step is the lowest-barrier process, while when the peri-substituent is bulky (CH3, Br, and C(CH3)3), the “isolated” rotation of the aryl group at the ap site has a lower barrier and is responsible for the observed dynamic NMR behavior. In the 1,3-di-t-butyl derivative, restricted rotation of the 1-t-butyl group was observed below −75 °C, the free energy of activation being 9.5 kcal mol−1.
  • Toshiari Morita, Michinori Oki
    1986 Volume 59 Issue 11 Pages 3605-3610
    Published: 1986
    Released: June 27, 2006
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    Rates of dissociation of the C–N bond in substituted 1-(1,3-dithiolan-2-yl)pyridinium ions in the perchlorate forms were obtained by the dynamic NMR technique in nitromethane-d3 and for one case in acetonitrile-d3. The study of the substituent effects on the rates of dissociation revealed that the rates were linearly correlated with the pKa values of the substituted pyridines. The mechanism of the dissociation was postulated to be of SN2 type, the perchlorate ion acting as a nucleophile, from the kinetic data.
  • Masaru Sato, Kaoru Suzuki, Sadatoshi Akabori
    1986 Volume 59 Issue 11 Pages 3611-3615
    Published: 1986
    Released: June 27, 2006
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    1,5,9-Trithia[9]ferrocenophane was prepared by the reaction of 1,1′-bis(3-chloropropylthio)ferrocene with sodium sulfide. The complexes of 1,5,9-trithia[9]ferrocenophane, along with 1,4,7-trithia[7]ferrocenophane, with copper(I), silver(I), mercury(II), and palladium(II) salts were prepared. Some interaction between the iron atom and the metal atoms coordinated to the thia-crown moiety was suggested from their spectral data in the solution for the complexes of 1,4,7-trithia[7]ferrocenophane with mercury(II) and palladium(II) salts and the complex of 1,5,9-trithia[9]ferrocenophane with silver(I) tetrafluoroborate.
  • Takayoshi Yamauchi, Kaneaki Hattori, Shoichi Mizutaki, Kentaro Tamaki, ...
    1986 Volume 59 Issue 11 Pages 3617-3620
    Published: 1986
    Released: June 27, 2006
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    Selenium tetrachloride(SeCl4) reacts smoothly with alcohols in various nonpolar solvents to give the corresponding alkyl chlorides in 44–97% yield. Similar reaction also proceeds with tellurium tetrachloride (TeCl4), while the treatment of benzyl, 1-phenylethyl, and t-butyl alcohols with TeCl4 in aromatic solvents results in a high yield formation of alkylated aromatics instead of alkyl chlorides. Such Friedel-Crafts aromatic alkylation hardly occurs in the SeCl4 case. The chlorinating species is not chlorine which might be evolved by dissociation of SeCl4 or TeCl4, but the metal chloride itself. The conversion of optically active (R)-(+)-1-phenylethanol to 1-phenylethyl chloride proceeds with nearly complete racemization.
  • Tomomichi Ishikawa, Makoto Otsuki, Toshiaki Iwatsuki
    1986 Volume 59 Issue 11 Pages 3621-3624
    Published: 1986
    Released: June 27, 2006
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    The preparation and α-chymotrypsin-catalyzed esterolysis of polymeric substrates anchoring fungicidal biphenyl-2-ol are described. In order to obtain information regarding the influence of one type of polymeric backbone and the distance between a cleavable bond and a polymer main chain, poly(2-biphenylyl acrylate), poly(2-biphenylyl methacrylate), and poly(methacryloylamino acid 2-biphenylyl ester)s were studied. The esterolysis were evaluated by means of Michaelis constant Km and the catalytic reaction rate constant kcat. Poly(2-biphenylyl methacrylate) was a more suitable substrate than poly(2-biphenylyl acrylate). Poly[6-(methacryloylamino)hexanoic acid 2-biphenylyl ester] was the most suitable substrate in a series of polymers containing amino acid side chains with 2-biphenylyl ester terminal groups. The release rate of biphenyl-2-ol could also be controlled by using copolymers with an appropriate comonomer.
  • Teruo Umemoto, Ginjiro Tomizawa
    1986 Volume 59 Issue 11 Pages 3625-3629
    Published: 1986
    Released: June 27, 2006
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    The reaction of sulfides possessing α-hydrogen with various N-fluoropyridinium salts was examined. While the fluorinating power increased in the order of N-fluoro-2,4,6-trimethylpyridinium triflate 1<N-fluoropyridinium triflate 2<N-fluoro-3,5-dichloropyridinium triflate 3, the yield of an α-fluoro sulfide decreased in the order of 1>2, and 3 no longer produced the α-fluoro sulfide. Triflate 1 was more reactive than the corresponding tetrafluoroborate 4. Thus, it was shown that 1 satisfactorily fluorinated various kinds of sulfides under very mild conditions, giving α-fluoro sulfides. A two-step mechanism, oxidative fluorination of sulfur and Pummerer-type rearrangement, was proposed for the fluorination. The corresponding α-fluoro sulfoxide or sulfones were easily prepared from the sulfides by successive fluorination–oxidation procedure.
  • Otohiko Tsuge, Shuji Kanemasa, Shigeori Takenaka
    1986 Volume 59 Issue 11 Pages 3631-3635
    Published: 1986
    Released: June 27, 2006
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    Pyridinium or isoquinolinium methylides undergo highly stereo- and regioselective cycloadditions with olefinic dipolarophiles to form unstable tetrahydroindolizine derivatives. One of the two double bonds existing in the dihydro heteroaromatic ring of the cycloadducts reacts with nitrile oxides, in the same flask, in stereo-, regio-, and periselective fashions to lead to stable isoxazole-fused tetrahydroindolizines in good yields.
  • Takayoshi Uematsu, Masao Umino, Shogo Shimazu, Masatoshi Miura, Hidehi ...
    1986 Volume 59 Issue 11 Pages 3637-3642
    Published: 1986
    Released: June 27, 2006
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    The process of the ligand release and the reduction of [Pd(NH3)4]-form sulfonic resin has been studied by chemical analysis, X-ray photoelectron spectroscopy and adsorption techniques. The removal of ammonia ligands remarkably increased with hydrogen treatment above 353 K, and was complete at around 393 K. It is suggested that the released ammonia partly transfers to –SO3 groups to form –SO3NH4 groups as the reduction proceeds. The dispersion of the metal particles prepared by hydrogen reduction ranged from 0.11 to 0.31 depending on the loading concentration of the palladium cation. The metal particles are considered to be entrapped in the pores of the resin. The formation of cationic palladium sites by the low temperature reduction is also suggested.
  • Chunshan Song, Masakatsu Nomura
    1986 Volume 59 Issue 11 Pages 3643-3648
    Published: 1986
    Released: June 27, 2006
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    The catalytic effects of MoCl3–LiCl–KCl and NiCl2–LiCl–KCl molten salts were studied for the hydroliquefaction of Morwell brown and Taiheiyo subbituminous coals at 400 °C for 1 h in a batch reactor with an initial hydrogen pressure of 9.8 MPa. The conversion to pyridine-soluble materials and the yield of hexane-soluble materials (HS) with the MoCl3 catalyst were 82 and 42% for Morwell coal, and 84 and 61% for Taiheiyo coal, respectively. The conversion and HS yield with the NiCl2 catalyst were 87 and 43% for Morwell coal, and 82 and 56% for Taiheiyo coal, respectively. The HS yield of the catalytic runs was about 2.6–3.2 times higher than that of noncatalytic runs. This finding established the effectiveness of the two new catalysts for the hydroliquefaction of brown and subbituminous coals. Detailed analyses of the reaction products have revealed that these catalysts promoted a depolymerization of the coals and strongly catalyzed the hydrocracking of polynuclear aromatic structures of heavy products into hydroaromatic and aromatic structures with smaller ring sizes. Most of these smaller hydroaromatic and aromatic structures did not undergo much further ring-opening reactions. This accounts for the high HS selectivity of the catalysts.
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