Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 71 , Issue 4
Showing 1-27 articles out of 27 articles from the selected issue
  • Ei-ichi Negishi, Tamotsu Takahashi
    1998 Volume 71 Issue 4 Pages 755-769
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Dialkylzirconocenes in situ generated such as Cp2Zr(n-Bu)2, Cp2ZrEt2, and Cp2Zr(t-Bu)(i-Bu) are thermolyzed to afford zirconocene-alkene complexes. In the cases of Cp2Zr(n-Bu)2 and Cp2Zr(t-Bu)(i-Bu), Cp2Zr-alkene complexes generated from them tend to act as a “Cp2Zr” equivalent, since the initially generated alkene is often replaced by another π-bond containing compound. In the presence of alkynes, for example, alkyne complexes may be generated. On the other hand, Cp2Zr(ethylene) tends to serve as an intermediate since the ethylene moiety is often incorporated in the final organic products. Ring expansion and contraction, ligand substitution, transmetallation, migratory insertion, stereoisomerization, regioisomerization, oxidative addition involving these Cp2Zr-alkene and Cp2Zr-alkyne complexes as well as their structures are reviewed.
  • Makoto Kuramoto, Koji Hayashi, Kohji Yamaguchi, Mika Yada, Tomoko Tsuj ...
    1998 Volume 71 Issue 4 Pages 771-779
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Norzoanthamine is a zoanthamine-type alkaloid from the colonial zoanthid Zoanthus sp. Norzoanthamine hydrochloride, which suppresses the decrease in bone weight and strength in ovariectomized mice, could be a good candidate for an osteoporotic drug. Although the relative configuration of norzoanthamine was established based on an X-ray crystallographic analysis, the absolute stereochemistry of norzoanthamine remains unclear. To investigate their biogenesis and mechanisms of biological action, we conducted chemical and spectroscopic studies to determine the absolute configuration of norzoanthamines.
  • Hideshi Nakamura, Yuko Kawase, Kyoko Maruyama, Akio Murai
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 781-787
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    In studies on the biogenesis of vasocontrictive macrolides, zooxanthellatoxins isolated from a symbiotic dinoflagellate Symbiodinium sp., we have investigated metabolites of the dinoflagellate cultured under different conditions. Four new compounds were isolated from 70% EtOH extract of the cells cultured in f/2 medium. Two betaines (zooxanthellabetaine-A and -B) were obtained from a neutral fraction of n-BuOH soluble portion and the structure of zooxanthellabetaine-A was determined as 4-(4-hydroxybenzoyloxy)-3-(trimethylammonio)butyrate. The EtOAc soluble portion afforded a new C-30 alkaloid, zooxanthellamine, and a new ceramide, symbioramide-C16. The structural similarity of zooxanthellamine to zoanthid alkaloids, zoanthamines, suggested an algal origin of these zoanthamines. Zooxanthellamine might be derived biogenetically from a polyketide chain presumably started from a glycine unit, like other marine toxins such as zooxanthellatoxin and palytoxin.
  • Yoshifumi Koide, Keigo Tsujimoto, Hideto Shosenji, Mizuo Maeda, Makoto ...
    1998 Volume 71 Issue 4 Pages 789-796
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Monomer-type functional surfactants, 2-(p-vinylbenzylamino)alkanoic acid (RnNAc) and N,N-dialkyl derivatives (RRnNAc), have been used as both a ligand and an emulsifier for the preparation of surface-template resins. The surfactants adsorbed at the toluene–water interface and emulsified divinylbenzene–styrene in a Cu2+ or Zn2+ solution. Emulsion polymerization using a K2S2O8 initiator (80 °C) or by irradiation with γ-rays gave fine particles of 200—800 nm in diameter. Metal-imprinted resins prepared with RnNAc and RRnNAc showed a high adsorptive capacity for the metal ion (surface-template effect). Cu-imprinted resins prepared with R8NAc were 2.69-times as effective for Cu2+ in competitive sorption from a Cu2+–Zn2+ mixture and Zn-imprinted resins were 1.84-times as effective for Zn2+, compared with unimprinted resins. Because of the great emulsifying power, metal-imprinted resins prepared with R8NAc showed the most metal-selective adsorption and the largest capacity among resins prepared with RnNAc and RRnNAc.
  • Hatsumi Mori, Shoji Tanaka, Takehiko Mori, Akiko Kobayashi, Hayao Koba ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 797-806
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Crystal structure analyses, band calculations, and electrical resistivity and magnetic susceptibility measurements have been carried out for new θ-type BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene; abbreviated as ET] salts, θ-(BEDT-TTF)2TlCo(SCN)4 and θ-(BEDT-TTF)2TlZn(SCN)4 [abbreviated as θ-TlCo and θ-TlZn], as well as crystal structure analyses of θ-(BEDT-TTF)2RbM′(SCN)4 [M′ = Co, Zn; abbreviated as θ-RbM′]. θ-TlCo and θ-RbM′ [M′ = Co, Zn] are isostructural to the previously reported θ-CsM′, and the metal-insulator transition temperature increases from 20 K (θ-CsM′ [M′ = Co, Zn]), 190 K (θ-RbM′) to 250 K (θ-TlCo) with decreasing the unit cell volume, namely, the inverse chemical pressure effect. A structural investigation for θ-RbM′ [M′ = Co, Zn] indicates a lattice a modulation at the metal-insulator transition temperature (190 K). For the other salt, θ-TlZn, a semiconductor–semiconductor transition has been observed at 165 K, where the behavior of the magnetic susceptibility, following the two-dimensional Heisenberg model, changes from J = −30 K to −57 K under a slow cooling condition.
  • Kazuchiyo Takaoka, Sigehiro Maeda, Hidetosi Miura, Kazunaka Endo, Dela ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 807-816
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Semiempirical HAM/3 MO program was used to obtain the theoretical valence X-ray photoelectron spectra (XPS) of the two leuco dyes (2′-anilino-6′-diethylamino-3′-methylspiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one (DEAMAF) and 3,3-bis(4-dimethylaminophenyl)-6-dimethylamino-1(3H)-isobenzofuranone (CVL)) and UV-visible adsorption spectra of the four leuco dyes (DEAMAF, CVL, 2′-chloro-6′-diethylamino-3′-methylspiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one (DEAMCF), and 3′,6′-bis(diethylamino)-spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one (Rhodamine B base). The calculated Al photoelectron spectra were obtained using Gaussian lineshape functions of an approximate linewidth 0.10Ek (Ek = Ek′ − WD), where Ek is the vertical ionization potential (VIP) of each MO and WD is a shift to account for sample work function, polarization energy and other energy effects. On the other hand, the absorption curves were simulated with Gaussian lineshape functions of a constant linewidth of 0.02 eV. The theoretical valence energy levels corresponded well to the spectra of two leuco dyes observed 0—40 eV, while the simulated adsorption spectra were shifted for a good fit with the experimental solution spectra in the range of 250—700 nm.
  • Yoshimi Sueishi, Hajime Inoue, Tetsuhito Oka, Hiroshi Tsukube, Shunzo ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 817-823
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The rate constants kex for the spin exchange of nitroxides with various kinds of cobalt(II) and nickel(II) complexes were determined from the EPR line-broadening of nitroxides. The rate constants estimated were in the range of 108—109 M−1 s−1 and this reaction was found to be diffusion-controlled. In order to distinguish cases of strong and weak spin exchange, we examined the pressure dependence of the spin exchange between nitroxide and the complexes. It was found that the ligand in the first coordination sphere of the complexes plays an important role for the efficiency of spin exchange. The presence of the coordinated halide ion provides strong exchange, regardless of any screening of the complex’s internal atoms by organic molecules. From the pressure dependence of kex, the J2fs values (the exchange integral J and the steric factor fs) for the spin exchange of nitroxides with cobalt and nickel complexes were estimated to be about 1020 s−2. Based on the results, the steric hindrance for the reaction of spin exchange is discussed.
  • Toshie Harazono, Etsuzo Yokota, Hiroshi Uchida, Tokuko Watanabe
    1998 Volume 71 Issue 4 Pages 825-829
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Luminous properties of a red phosphor, Eu–Y2O3 (Eu-doped Y2O3) have been studied by 89Y (nuclear spin 1/2)-static NMR. Pure Y2O3 showed an anisotropic pattern with the peak centered at 299 ppm assigned to the Y atom in the site, where none of the 12 nearest neighbouring Y atoms are substituted by an Eu atom. The signal became broader with increasing doped Eu content. Additionally, a shoulder peak assigned to the Y atom in the site where one of the 12 nearest neighbouring Y atoms was replaced by one Eu atom appeared around 100—110 ppm in the samples with more than 1 mol/% Eu content.
    The spin–spin relaxation of the centered signal was mainly dominated by the dipole–dipole interaction mechanism between the 89Y nucleus and the paramagnetic electrons of Eu3+ with 4f6 electron configuration which substituted at the second nearest and further neighbouring Y. In conclusion, the line-broadening of 89Y signal at constant Eu content was correlated with the Eu distribution on the basis of the facts that the phosphor sample with higher brightness showed broader linewidth and the intensity of the ESR signal corresponding to the lattice defects has no relation to the brightness.
  • Akihito Imanishi, Toshihiko Yokoyama, Yoshinori Kitajima, Toshiaki Oht ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 831-835
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The surface structure and electronic properties of 0.07 ML thiophene (C4H4S) adsorbed on Cu(111) have been investigated by means of S K-edge X-ray-absorption fine structure measurements. The results are comparatively discussed with the previously studied C4H4S/Cu(100) case. It is found that C4H4S molecules are adsorbed with the molecular plane parallel to the surface, as in the Cu(100) substrate. The S–Cu distance is 2.50 ± 0.02 Å, which is significantly longer than that of Cu(100) (2.42 ± 0.02 Å), while the S–C bond distance is 1.71 ± 0.04 Å, somewhat shorter than the Cu(100) one (1.74 ± 0.04 Å). Correspondingly, a smaller amount of charge transfer of (0.5 ± 0.2) electron from the substrate to the C4H4S π* orbital is estimated compared to the Cu(100) case of (1.0 ± 0.2) electron. These findings indicate a considerably weaker interaction of thiophene with Cu(111) than with Cu(100), due to a more closely packed surface of Cu(111).
  • Yoshiyuki Morioka, Taka-aki Hisamitsu, Hidenari Inoue, Naoki Yoshioka, ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 837-844
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    A long-living metastable state is produced in FeII[Fe(CN)5NO]·xH2O by an irradiation of 488 nm light at 200 K. A strong near-infrared band of about 10000 cm−1 and a ν(CN) band at 2070 cm−1 that newly appear in the metastable state point to development of the mixed-valence state analogous to Prussian blue. An iron-to-nitrosyl charge transfer in pentacyanonitrosylferrate(2−), [Fe(CN)5NO]2−, explains the formation of the mixed-valence state, because the charge transfer causes a pair of iron(II) and iron(III) atoms bridged by CN that has the same local structure as Prussian blue. In addition to the formation of the metastable state, the prolonged irradiation causes an irreversible change of FeII[Fe(CN)5NO]·xH2O and leads to the formation of a photoproduct. The photoproduct also has infrared spectra characteristic of the mixed-valence state. Mössbauer spectra of the photoproduct show that a low-spin iron ion in pentacyanonitrosylferrate(2−) is divalent and a high-spin iron outside of pentacyanonitrosylferrate(2−) is trivalent. Therefore, the charge-transfer between the two non-equivalent iron ions is thought to follow the intra-molecular charge transfer in pentacyanonitrosylferrate(2−).
  • Masayoshi Nakano, Satoru Yamada, Kizashi Yamaguchi
    1998 Volume 71 Issue 4 Pages 845-850
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The static second hyperpolarizability (γ) for a symmetric open-shell system including nitroxide radical groups, nitronyl nitroxide radical, has been studied using ab initio molecular-orbital methods, including various electron-correlation effects. This system is predicted to exhibit a negative γ by our classification rule of γ based on symmetric resonance structures with inversible polarization (SRIP). A remarkable electron correlation dependence has been observed in the magnitude and sign of γ, which has been found to be negative by using high-order electron correlation methods. This tendency has also been investigated in terms of the second hyperpolarizability density, which is defined as the third-derivative of the charge density with respect to the applied electric field.
  • Motonori Matsuno, Hideo Takeuchi
    1998 Volume 71 Issue 4 Pages 851-857
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    UV resonance Raman intensities of indole ring vibrations were examined in solutions of different solvent properties to establish the correlation between the intensity and the environment of the indole ring, the main side-chain component of amino acid tryptophan. Each of the Raman bands that are enhanced through resonance with the Bb electronic transition gives the highest intensity when the indole NH site is hydrogen-bonded with a proton acceptor in hydrophobic environments. On the other hand, the Raman bands that gain intensity through resonance with the La transition are most enhanced when the indole ring is not hydrogen-bonded. Although these changes in Raman intensity result from small red and blue shifts of the Bb and La absorptions, respectively, the Raman intensity changes are much greater than the changes in UV absorption spectra. UV resonance Raman intensities are thus expected to be useful markers of hydrogen bonding and hydrophobic interactions of tryptophan residues in proteins.
  • G. B. Kolekar, M. A. Anuse
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 859-866
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    A method is proposed for the extraction, separation and spectrophotometric determination of trace levels of tellurium(IV) from hydrochloric acid media with 1-(4-bromophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol (4-bromoPTPT) in chloroform. The yellow-colored complex absorbs at 440 nm and the system obeys Beer’s law in the 1—15 ppm concentration range. The molar absorptivity and Sandell’s sensitivity are 8.1 × 103 dm3 mol−1 cm−1 and 16 ng cm−2, respectively. The probable composition of the extracted species is TeL2. The interference of various ions was studied. Various parameters, such as the effects of the acidity, reagent concentration, equilibration time etc., have been established for the extractive spectrophotometric determination of tellurium(IV). The method has been applied for the determination of tellurium(IV) in various synthetic samples corresponding to alloys, and provides for the binary separation of tellurium(IV) from lead, bismuth, copper, gold, and antimony. It is also applicable for the simultaneous determination of selenium(IV) and tellurium(IV). The method is accurate, simple, rapid, and selective, and the overall process of extraction and determination takes about 15 to 20 min.
  • Masato Kurihara, Stephane Daniele, Kiyoshi Tsuge, Hideki Sugimoto, Koj ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 867-875
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    A series of [RuX(dioxolene)(terpy)] (terpy = terpyridine; X = Cl, OAc) and one-electron oxidized complexes were prepared. The molecular structures of [RuCl(O2C6H2-3,5-Bu2)(terpy)] (1) and [Ru(OAc)(O2C6H4)(terpy)] (3) were determined by X-ray crystallography. Crystal data for 1: monoclinic, space group P21/c, Z = 8, a = 11.548(1), b = 18.224(5), c = 30.002(8) Å, β = 96.51(2)°, and R = 0.077 (Rw = 0.068). Crystal data for 3: monoclinic, space group C2/c, Z = 8, a = 13.355(5), b = 12.131(4), c = 26.645(4) Å, β = 92.46(2)°, and R = 0.041 (Rw = 0.041). Although the binding mode of O2C6H2-3,5-Bu2 to Ru was not determined by the molecular structure of 1, the carbon–oxygen and carbon–carbon bond lengths of O2C6H4 in 3 were consistent with those of catecholato ligands. Electronic absorption spectra of [RuX(dioxolene)(terpy)] were explained by the electronic structure of [RuIIX(semiquinone)(terpy)] rather than [RuIIIX(catecholato)(terpy)], while the reverse assignment was deduced from the IR spectra. Moreover, ESR spectra showed hyper-fine structures due to the contribution of semiquinone superimposed on an axial pattern of the Ru(III) center, indicating a resonance equilibrium between [RuIIX(semiquinone)(terpy)] and [RuX(dioxolene)(terpy)].
  • Saisuke Watanabe, Hiroshi Hiraike, Hideo Kurosawa
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 877-881
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    [Pd{η3-CH2C(CH2Cl)CH2}(μ-SPh)]2 is spontaneously transformed, in MeCN, into [Pd{η3-CH2C(CH2SPh)CH2}(Cl)]2, which has a novel thioether-bridged dimeric structure. This transformation is suggested to proceed by an attack of the thiolate anion at the methylene carbon bearing a Cl substituent of an ionic intermediate, [Pd{η3-CH2C(CH2Cl)CH2}(MeCN)2]+. [Pd{η3-CH2C(CR2Cl)CH2}(μ-SPh)]2 (R = H, Me) reacts with PPh3 to give [Pd{η3-CH2C(CH2SPh)CR2}(Cl)(PPh3)]. This transformation proceeds via an attack of the thiolate anion at the terminal allyl carbon of an ionic intermediate, [Pd{η3-CH2C(CH2Cl)CH2}(PPh3)2]+, to give 2-phenylthiomethylallyl chloride, which undergoes an oxidative addition to the resulting Pd(0) complexes. [Pd{η3-CH2C(CR2Cl)CH2}(Cl)(PPh3)] (R = H, Me) reacts with Bu3SnCH=CH2 to give [Pd{η3-CH2C(CH2CH=CH2)CR2}(Cl)(PPh3)] through a reductive elimination–oxidative addition sequence, starting from an intermediate, [Pd{η3-CH2C(CR2Cl)CH2}(CH=CH2)(PPh3)].
  • Masahiko Inamo, Kiyohiko Nakajima
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 883-891
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    A structural, thermodynamic, and kinetic study of a chromium(III) complex of 5,10,15,20-tetraphenylporphyrin, [Cr(tpp)(Cl)(L)], where L represents an imidazole ligand, is presented. The present study is aimed at elucidating the effect of a steric strain induced by the 2-methyl substituent of the imidazole ligand on the molecular structure and the dynamics of an axial ligand-substitution reaction. Crystals of the 1-methylimidazole complex [Cr(tpp)(Cl)(1-Meim)] (1) and 1,2-dimethylimidazole complex [Cr(tpp)(Cl)(1,2-Me2im)] (2) were obtained from a dichloroethane–toluene mixture containing a slight excess of imidazole ligand in the monoclinic space group Cc, Z = 4, a = 18.306(2), b = 13.311(2), c = 21.391(5) Å, β = 120.05(1)°, V = 4512(1) Å3, and in the orthorhombic space group P212121, Z = 4, a = 9.926(1), b = 17.902(3), c = 25.247(4) Å, V = 4486(1) Å3, respectively. The axial Cr–Nim bond lengths for 1 and 2 are 2.103(4) and 2.139(5) Å, respectively. A steric hindrance has been demonstrated by a 0.036 Å increase in the Cr–Nim bond length and a tilting and tipping of the imidazole ligand of 2 from the symmetrical position observed in 1. The substitution reaction of the axial pyridine ligand of [Cr(tpp)(Cl)(py)] by various imidazole ligands was studied spectrophotometrically in dichloromethane or in toluene. A steric effect due to the 2-methyl substituent of the imidazole ligand was observed along with an increase in the ligand-dissociation rate and a decrease in the binding constant of the imidazole ligand to the metalloporphyrin. These results were examined in terms of steric interactions between the axial ligand and the porphyrin core.
  • Masaru Kimura, Rie Ikawa, Yuko Shiota, Keiichi Tsukahara
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 893-897
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Although the chromate(VI) ions, CrO42− and HCrO4, which are described as CrVI herein, could hardly oxidize the iodide ion to iodine above pH 3.0, it was catalytically oxidized by adding traces of copper(II) ion. When a copper(II) solution of 10−7—10−5 mol dm−3 was mixed with an iodide solution, after a fast formation of iodine, the iodine concentration remained constant. After such an iodine formation had occurred, if a chromate solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2/3(d[I2]/dt) = −d[CrVI]/dt = k[CuI][CuVI], in which [CuI] is the steady-state concentration in the chain cycle CuI+/CuI. The rate of the chain reaction was independent of the time to add chromate, and the formation of iodine I2 (or triiodide ion I3) stopped at the time when all of the chromate was consumed by the chain reaction. The stoichiometry was 3I + CrVI → 1.5I2 + CrIII. The iodine formation was extremely inhibited by the presence of either radical scavengers or complex-forming reagents as well as by increasing pH. Although addition of alcohols to the reaction mixture extremely accelerated the iodine formation before adding chromate, it hardly affected on this process after the addition of chromate. The reaction mechanisms are presented in order to account for the observed results.
  • Rastko D. Vukicevic, Ljubinka Joksovic, Stanimir Konstantinovic, Zoran ...
    1998 Volume 71 Issue 4 Pages 899-904
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The acylation of some alicyclic and aliphatic alkenes by the electrochemical generation of a catalyst using a sacrificial aluminum anode was investigated. Substrates were electrolyzed in a dichloromethane solution of an appropriate electrolyte (tetraalkylammonium salts) in the presence of an acylating agent (acetyl chloride or anhydride). Thus, unsubstituted cycloalkenes, namely cyclohexene and cycloheptene, gave by that reaction conjugated ketones, i.e. the corresponding 1-acetylcycloalkenes, as the only unsaturated carbonyl compounds in moderate-to-good yields. Under the same reaction conditions their 1-methyl derivatives gave mixtures of the corresponding conjugated and β,γ-unsaturated isomeric ketones in which unconjugated compounds predominate. In both cases unsaturated ketones were accompanied by different amounts of side products. Terminal aliphatic alkenes (1-hexene, 1-heptene, and 1-dodecene) afforded only conjugated a ketone with a normal skeleton, but in lower yields. The acylation of cyclohexene was studied in more detail, altering the reaction conditions by changing the reaction temperature, the supporting electrolyte, the acylating agent and the electrochemical cell. Mechanistic considerations were made on the basis of the products distribution and some theoretical calculations being made by the MOPAC program package (version 7.0).
  • Nasser Iranpoor, Habib Firouzabadi, Mohammad Ali Zolfigol
    1998 Volume 71 Issue 4 Pages 905-908
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Fe(NO3)3·1.5N2O4 is a highly efficient reagent for the oxidation of various classes of hydroxy compounds in dichloromethane at room temperature, or in the absence of solvent. Cu(NO3)2·N2O4 oxidizes different hydroxy compounds in refluxing carbon tetrachloride and is a highly selective reagent for oxidation of primary benzylic alcohols in refluxing EtOAc.
  • Tomotaka Nakamura, Katsuhiko Takagi, Yasuhiko Sawaki
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 909-914
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The photochemistry of trans-cinnamic acid (trans-1) was studied in a cast film of dimethyldioctadecylammonium bromide (2), deposited from aqueous dispersions as a crystalline solid by the spontaneous vaporization of water. UV irradiation of the cast film resulted in a highly selective formation of the syn-Head-to-Head dimer, suggesting a parallel orientation of trans-1 within a bilayer film. Analyses with X-ray diffraction, differential scanning calorimetry, and IR spectra revealed the formation of a bilayer structure of 2 in which the molecules of trans-1 are dissolved to interact with 2 of the polar head groups. The photoreactivity of trans-1 in the cast film was found to be dramatically suppressed by heating at 40—60 °C, which is attributed to an improvement in the crystallinity of the bilayer.
  • Michinori Oki, Hiroshi Ikeda, Hiromichi Miyake, Hirohito Mishima, Shin ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 915-926
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Rates of topomerization in α-chlorobenzyl ethyl ether and its p-methyl as well as p-methoxy derivatives were determined in various solvents by the dynamic NMR method. The topomerization process was deduced to be ionic because the rates are enhanced in polar solvents as well as by electron-donating substituents. Concentration dependence study of the topomerization in carbon tetrachloride revealed that the observed process is unimolecular; the rates are not affected by concentration of the substrate if the concentration is lower than 0.2 mol L−1. The rates of topomerization are smaller for solutions in bulky solvents than in small solvents, the effects being clear for compounds with electron-donating substituents. The key feature of the kinetic parameters is that the entropy of activation is large and negative for all the solvents examined. The reaction mechanisms are discussed on the basis of these data. The effects of the molecular size of the solvent, dimensiosolvatic effects, are attributed to the effectiveness of the solvation in the formation of ion pairs. The results show that thermolyses of alkyl α-chlorobenzyl ethers are much slower reactions than the ionization. The nature of the reaction is discussed.
  • Shinro Yasui, Munekazu Tsujimoto, Mutsuo Okamura, Atsuyoshi Ohno
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 927-932
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Peak oxidation potentials of acyclic and cyclic phosphinites, phosphonites, and phosphites were measured by cyclic voltammetry. The inductive effect of the ligands attached to the phosphorus is a primary factor to determine of these compounds. The geometry of the compound is another important factor; is lowered when the compound adopts a geometry in which the phosphorus lone-pair orbital overlaps with the adjacent oxygen p-orbital. The stereoelectronic effects found here are interpreted in terms of the energy level of the highest occupied molecular orbital (HOMO) of these phosphorus compounds.
  • Wonchull Han, Mitsuhiro Hibino, Tetsuichi Kudo
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 933-937
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Two types of crystalline (NH4)10[H2W12O42]·10H2O were precipitated in sequence when an ammonia solution of peroxopolytungstate was neutralized with hydrochloric acid. It was found by X-ray diffraction that one of them is an unknown phase of ammonium paratungstate, and the other is the reported one. Heating the former, it turned directly to common triclinic WO3. On the other hand, the latter yielded the hexagonal form of WO3 (h-WO3) in the temperature range 350—370 °C. This is a new synthetic method of h-WO3, though the final precursor is a known compound. The color of h-WO3 thus formed was pale yellow and contained a small amount of residual ammonia (N/W = 0.017 in molar ratio). Its crystallographic c-axis (7.689 Å) was shorter than than the reported value (7.798 Å) for the same WO3 phase synthesized from 3WO3·H2O.
  • Zhi-hong Zhao, Yoshikazu Sakagami, Tetsuya Osaka
    1998 Volume 71 Issue 4 Pages 939-945
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    The inhibitory capability of various low concentrations of six kinds of metal ions [silver(I), copper(II), cobalt(II), nickel(II), zinc(II), and dichromate] for pathogenic bacterial (gram-positive bacteria Staphylococcus aureus and MRSA, gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa) growth was quantitatively determined exactly. Residual metal-ion concentrations in a phosphate buffer solution after being incubated with pathogenic bacteria were then measured by an atomic-absorption spectrophotometer. We found that the inhibitory capability of metal ions correlated with the residual metal concentrations. Based on the biochemical and chemical situation, the mechanisms of the inhibitory capability of the metal ions are discussed. In addition, the determined minimum inhibitory concentration (MIC) values of metal ions on tested bacteria are considered.
  • Jie Wang, Noritaka Mizuno, Makoto Misono
    1998 Volume 71 Issue 4 Pages 947-954
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    A comparative study of NO and N2O decomposition over Cu/ZSM-5 and Cu/Y zeolites with various Cu loading levels has been carried out at 523—823 K. The Arrenhius plot of NO decomposition tended to level off above 773 K, as reported in the literature, while that of N2O decomposition was linear. It was noted that the reactivity of N2O decomposition rose much more sharply than that of NO decomposition with an increase in the level of the copper-ion exchange. The implications of these results on the reaction mechanism were discussed. In addition, the adsorption of NO on Cu/ZSM-5 and Cu/Y was measured by IR at 173—373 K and the results were compared with the catalytic decomposition results.
  • Hitoshi Nakajima, Hitoshi Tanaka, Mitsuhiro Hibino, Tetsuichi Kudo, No ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 955-960
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Reactions of nitrides of Mo, W, V, and Ti with hydrogen peroxide, especially Mo and W, were investigated. The reactions were characterized by elemental analysis, NMR, IR, Raman, XPS, TOF mass, and TG/DTA spectroscopy and titration of ammonia and peroxo group. The major oxometalate species in reaction solution for Mo and W were [MoO(O2)2(OOH)]22− and [W2O3(O2)4(H2O)2]2−, respectively. As for the nitrogen-containing species, ammonium ions were initially formed, followed by the nitrate ions. Protons formed by the reaction take part in the formation of ammonia. The removal of unreacted hydrogen peroxide and the evaporation to dryness resulted in the formation of isopolymetalates. The peroxooctamolybdate, peroxododecatungstate, and decavanadate were suggested to be formed. Among them, the peroxopolytungstate was the most thermally stable and provided homogeneous thin films. The films showed protonic conductivity and the logarithm of conductivity changed linearly with the relative humidity or the inverse of the temperature.
  • Shinzo Kohjiya, Hideki Tsubata, Kenji Urayama
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 4 Pages 961-971
    Published: 1998
    Released: February 01, 2006
    JOURNALS RESTRICTED ACCESS
    Copolymeric networks composed of two chemically different network chains, polydimethylsiloxane (PDMS) and polyethylene oxide (PEO), are prepared by the two synthetic methods: (1) Vinyl-terminated PDMS and PEO are end-linked with the multi-functional silane compounds; (2) Vinyl-terminated PEO and silyl-terminated PDMS are end-linked with each other. The compositions in the resulting two-component networks are determined by two independent methods: 1H NMR analysis of the extracted unreacted materials and thermogravimetric analysis of the network samples. The appearances of the copolymeric networks are transparent. The differential scanning calorimetry and dynamic mechanical analysis show that the copolymeric networks have the microphase separated structures composed of PDMS and PEO phases. Swelling experiments in various solvents clearly indicates the amphiphilic character of the copolymeric networks. The Li-doped copolymeric networks, which are obtained by immersing the gels in LiClO4, exhibit conductivity of the order of 10−6 S cm−1 at room temperature. The temperature dependence of the conductivity obeys the William–Ferry–Landel equation based on the free volume theory.
feedback
Top