Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 57 , Issue 10
Showing 1-50 articles out of 74 articles from the selected issue
  • Michio Kobayashi, Toshiyuki Kasahara, Keihachiro Nakajima, Kazunori Ma ...
    1984 Volume 57 Issue 10 Pages 2695-2699
    Published: 1984
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Absorption spectra of a nematic liquid-crystalline molecule (4-butyl-4′-ethoxyazobenzene) were measured in sandwich-type cells with very thin gaps which ranged from 0.2 to 1.0 μm when the cells were empty. The intensity ratio of the first (354 nm) to second (240 nm) band in the liquid state (86 °C) decreases as the state changes into liquid-crystalline (LC) states (70 and 48 °C). According to results of dichroism analysis and MO calculation, the 354 nm and 240 nm bands are due to π-π* transitions polarized along the molecular long and short axes, respectively (with an angle of about 66°to each other). This finding coupled with an assumption that the molecular orientation of the liquid state is isotropic, allows a qualitative discussion on the orientation of molecule in the LC state, leading to a conclusion that the molecular long axis against the cell surface takes two kinds of orientation with respective tendencies to be parallel in the interface region and perpendicular in the bulk region.
  • Sanyo Hamai
    1984 Volume 57 Issue 10 Pages 2700-2702
    Published: 1984
    Released: June 27, 2006
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    Intrinsic fluorescence yields of exciplexes, φf0, have been determined for halogenated systems of anthracene (A)–N,N-dimethylaniline (DMA) in cyclohexane. By the substitution of a chlorine atom for a hydrogen atom in either A or DMA, φf0 is reduced to about 1/5, whereas by the bromine substitution it is reduced to about 1/80. When more than one halogen atom of the same kind are substituted in the A–DMA exciplex, the first substitution causes more prominent reduction in φf0 than the subsequent substitution does. Although there is a remarkable irregularity in the fluorescence quantum yields of halogenated anthracenes which were used as the electron acceptors in the exciplexes, φf0 varies regularly according to the kind and the number of the halogen substitutions. The internal heavy atom effect on φf0 is explained by the enhancement of the intersystem crossing rate to the triplet state.
  • Kazuyoshi Ueda
    1984 Volume 57 Issue 10 Pages 2703-2711
    Published: 1984
    Released: June 27, 2006
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    Reversing-pulse electric birefringence (RPEB) signals of poly(γ-methyl L-glutamate) (PMLG) were measured, for the first time, in hexafluoro-2-propanol at 25 °C and at 535 nm. Quantitative analyses were carried out on the steady-state birefringence and the field-free decay time (<τ>EB) in the wide field strength region and also on the rise, reverse, and decay portions in the low field strength region by taking into account the continuous molecular length distribution of a fractionated PMLG sample. The weight-average length (lw), permanent dipole moment (μw), polarizability anisotropy (Δαw), and the degree of polydispersity (lw/ln) were evaluated by two procedures: one from the analysis of the reverse-transient portion and the other from the field-free decay portion of RPEB signals. These two sets of the parameters should be identical with each other, if the electrooptical and hydrodynamic properties of PMLG do not change during the field-on and field-off processes. However, the length of the PMLG helix is shorter by about 18% in the presence of an electric field than that in the absence of the field. In order to explain this discrepancy, a new concept of reversible conformational transition under the external electric field is introduced.
  • Naohisa Kure, Hitoshi Nakatsuji, Takayuki Sano, Tatsuya Yasunaga
    1984 Volume 57 Issue 10 Pages 2712-2717
    Published: 1984
    Released: June 27, 2006
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    The interaction of Cu2+ ion with bovine serum albumin (BSA) was studied statically by equilibrium dialysis and ultraviolet spectrophotometric titration techniques, and kinetically by the stopped-flow method with transmittance detection at 255 nm. The static measurements showed the presence of one primary binding site and a number of weaker binding sites at pH 5.2. Stopped-flow measurements were undertaken in the pH region of 4–6.4 where a single reaction process was observed on the order of several seconds following the rapid absorbance change within the dead-time of the apparatus. This single reaction process was attributed to reaction of Cu2+ ion with the primary BSA site. The analyses of pH and concentration dependences of both the relaxation time and absorbance change confirmed the presence of two types of bound Cu2+ species to the primary binding site. One type formed during the dead-time of the apparatus is postulated as a square-planar complex formed between Cu2+ and the three N-terminal peptides of BSA. This reaction occurs with Cu2+ being exchanged for hydrogen ions on the N-terminal peptides. The second type of bound Cu2+, observed by stopped-flow method is thought to result from a bimolecular binding of Cu2+ ion a deprotonated imidazolyl group in the third position of the histidyl residue; the value of the molar extinction coefficient for this species, determined kinetically, suggests a further coordination of the β-carboxyl group to the bound Cu2+.
  • Michiko Yoshioka, Takashi Maekawa, Toshio Yokokawa
    1984 Volume 57 Issue 10 Pages 2718-2720
    Published: 1984
    Released: June 27, 2006
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    The Fe Kβ1,3 energy shifts in the binary sodium borate, silicate, and phosphate glasses containing small amounts of the iron ion were examined. The Fe Kβ1,3 energy decreases with an increase in the sodium oxide content in the borate and silicate glasses. The data are in accordance with those of previous studies that the coordination number of the Fe(III) ion is four in the borate and silicate glasses and six in the phosphate glasses. The structure of the coordination sphere around the Fe(III) ion in the borate glasses was also discussed.
  • Koichi Segawa, Katsumi Ooga, Yasuhiko Kurusu
    1984 Volume 57 Issue 10 Pages 2721-2724
    Published: 1984
    Released: June 27, 2006
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    The molybdenum peroxide (Mo-y) prepared by oxidation of molybdenum metal with hydrogen peroxide has been studied to determine its structure and thermal behavior. Temperature programmed decomposition has been used to study the thermal stability of Mo-y. Two distinct peaks, I and II, of decomposition processes are discernible in Mo-y. Peak I corresponds to the elimination of water of crystallization and peak II to the decomposition of a peroxide ion of Mo-y. IR and UV examinations support the results of the thermal analysis. The IR band at 931 cm−1 and the UV band at 381 nm show the same thermal behavior. Both bands are attributable to the peroxide ion of Mo-y. Spectroscopic studies show that Mo-y has the tetrahedral coordination derived from the single molybdenum complex, which has double bond oxygens attached to Mo atom and has a symmetric type of peroxide ion with one water of crystallization.
  • Kiyofumi Nagai, Reiko Nakamura, Mamoru Shimoi, Akira Ouchi
    1984 Volume 57 Issue 10 Pages 2725-2729
    Published: 1984
    Released: June 27, 2006
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    Five isomorphous lanthanoid(III) complexes were synthesized, and the structure of the terbium (1) and erbium (2) complexes were determined by the use of the single-crystal X-ray diffraction method. Crystals of 1 and 2 are monoclinic, with the space group P21/n, and the cell constants are: (1) a=25.076(8), b=15.446(3), c=14.579(8) Å, β=100.77(4)°; (2) a=25.036(20), b=15.228(4), c=14.805(19) Å, β=99.50(12)°. The structures were solved by the heavy-atom method and refined by the block-diagonal least-squares method. The final R values of 1 and 2 are 0.061 and 0.055 respectively. They consist of discrete complex cations and dithiophosphate anions. The central metal atom of the cationic complex is hepta-coordinated, and it is in a pentagonal bipyramidal geometry, where four sulfur atoms of two dithiophosphate ions and one oxygen atom of a benzamide ligand take the equatorial positions, while two benzamide oxygen atoms are in the axial positions.
  • Hiroshi Sawase, Yukio Koizumi, Yasuo Suzuki, Mamoru Shimoi, Akira Ouch ...
    1984 Volume 57 Issue 10 Pages 2730-2737
    Published: 1984
    Released: June 27, 2006
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    The M–O bond lengths and some bond angles of the acetato ligands in the title compounds were compared with each other using their structural data as obtained by the single-crystal X-ray diffraction method. With the increase in the atomic number of the central metal atom, the length of the weakest M–O bond in the bridge increases, even though all the other M–O bonds are shortened. This fact can be explained as follows: as the number of ligating oxygen atoms around the central metal atom is almost at a maximum in these complexes, the sharing space of the tenth coordinating atom on the coordination sphere decreases when the radius of the central metal atom is shortened as a result of the lanthanoid contraction effect.
  • Tetsu Kumagai
    1984 Volume 57 Issue 10 Pages 2738-2740
    Published: 1984
    Released: June 27, 2006
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    The distribution behavior of the zinc ion in sodium bromide and iodide solutions between the cation-exchange resin for forced-flow liquid chromatography and the absolute or aqueous ethylene-glycol phase was investigated radiometrically. From the experimental data, consecutive complex formation constants for zinc bromide and iodide in the glycol have been calculated by the nonlinear least-squares method. The results are as follows: in absolute glycol β1Br=2.60 and β2Br=3.91 for zinc bromide, β1I=2.36 and β2I=3.04 for zinc iodide; in 5 wt% aqueous glycol β1Br=2.30, β2Br=3.32, and in 10 wt% aqueous glycol, β1Br=1.87, β2Br=2.78, respectively.
  • Kenji Sano, Takakazu Yamamoto, Akio Yamamoto
    1984 Volume 57 Issue 10 Pages 2741-2747
    Published: 1984
    Released: June 27, 2006
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    Metal containing cyclic ester complexes, (Remark: Graphics omitted.)(L=1,2-bis(diphenylphosphino)ethane (dpe) or 2,2′-bipyridine (bpy); R1, R2=H or CH3) and (Remark: Graphics omitted.) (L=tricyclohexylphosphine (PCy3) or dpe; n=1 or 2), have been prepared by oxidative addition of cyclic carboxylic anhydrides to zero-valent metal complexes. These complexes have been characterized by elemental analysis and spectroscopies (IR as well as 1H-, 13C{1H}-, and 31P{1H}-NMR) and chemical reactivities. Rate of the oxidative addition of succinic anhydride to Ni(bpy)(cod) (cod=1,5-cyclooctadiene) is expressed by a second order rate equation, R=k[Ni(bpy)(cod)][succinic anhydride], and temperature dependence of k gives the activation energy of 68 kJ mol−1. The reaction of methylsuccinic anhydride with Ni(cod)2 in the presence of tertiary phosphine or bpy affords two isomers, (Remark: Graphics omitted.) and (Remark: Graphics omitted.), corresponding to two modes of C–O bond cleavage in methylsuccinic anhydride promoted by Ni; dependence of the ratio between the two isomers on the kind of ligand added and reaction conditions has been examined.
  • Tatsuya Sekine, Tohru Yoshikata, Takashi Saitou
    1984 Volume 57 Issue 10 Pages 2748-2750
    Published: 1984
    Released: June 27, 2006
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    The liquid–liquid distribution equilibria of perchioric, nitric, and picric acids between water and 4-methyl-2-pentanone or 4-methyl-2-pentanol have been determined at 298 K by measuring the concentrations of the anions in the two phases by spectrophotometry. The distribution ratio always increased on increase of the acid concentration; this was explained in terms of an increase in the degree of association of the acids in the organic phase. It was concluded from the analysis of the distribution data that the dissociation constant of perchloric acid was the highest and the value of picric acid was higher than that of nitric acid in 4-methyl-2-pentanone. The dissociation constant of picric acid was also higher in 4-methyl-2-pentanol than that of nitric acid; it was similar to that of perchloric acid. The differences of the dissociation constants were larger in 4-methyl-2-pentanone than in 4-methyl-2-pentanol.
  • Masutaro Suzuki, Osamu Arisato, Ken-ichi Okamoto, Hisahiko Einaga, Jin ...
    1984 Volume 57 Issue 10 Pages 2751-2756
    Published: 1984
    Released: June 27, 2006
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    Three kinds of cobalt(III) complexes with S-(2-aminoethyl)-L-homocysteinate (L-aehc) and a bidentate ligand (glycinate, oxalate, and ethylenediamine) were prepared and chromatographically separated into the quasi-enantiomeric isomers: ΔL-trans(Omer(N)-R(S), ΔL-cis(Omer(N)-R(S), ΛL-cis(Omer(N)-S(S), and ΛL-cis(Ofac(N)-S(S) for the glycinato complex, ΔL-trans(N)-R(S) and ΛL-cis(N)-S(S) for the oxalato one, and ΔL-R(S) and ΛL-S(S) for the ethylenediamine one. These isomers were characterized from their electronic absorption, CD, and 13C NMR spectra. The conformations of the six-membered N–S chelate ring in the L-aehc, of the chair for ΔL-R(S) and of the chair or skew-boat for ΛL-S(S), were suggested on the basis of the 13C NMR spectra. The CD spectra of the isomers are discussed in relation to their geometrical and absolute configurations.
  • Mitsuru Sano, Tetsuya Maruo, Hideo Yamatera
    1984 Volume 57 Issue 10 Pages 2757-2760
    Published: 1984
    Released: June 27, 2006
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    A laboratory EXAFS system with a curved crystal has been developed. This apparatus consists of a usual X-ray tube, a spectrometer with a Johan-type curved crystal, and two proportional counters detecting the X-rays. The resolution and performance tests have been carried out and excellent spectra have been obtained for NiO. With this system, aqueous solutions of ammine and ethylenediamine nickel(II) salts have been studied. The spectra were analyzed by the curve-fitting method by reference to the spectra of appropriate crystals containing the corresponding complexes. The values obtained for the Ni–N distances are 2.12±0.01 Å. These values are very close to those of the corresponding complexes in crystals.
  • Yoshihiro Shigemasa, Yoshihiro Sasaki, Nasuo Ueda, Ruka Nakashima
    1984 Volume 57 Issue 10 Pages 2761-2767
    Published: 1984
    Released: June 27, 2006
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    Dihydroxyacetone (DHA) was obtained in good yield from the selective formose reaction which was conducted with 2-(dimethylamino)ethanol and vitamin B1 in N,N-dimethylformamide (DMF). The major products were isolated from the formose and identified as dihydroxyacetone and 2-(1,2-dihydroxyethyl)-5-(2-hydroxyethyl)-4-methylthiazole by spectral data. Vitamin B1 suppressed the vaporization of formaldehyde from the reaction solution. Irrespective of the 2-(dimethylamino)ethanol concentration (above 0.1 M (1M=1 mol dm−3)), the maximum yield of DHA was 80–90 glc% at 1.0 M formaldehyde concentration, when the formaldehyde consumption was above 90%. Above 3.0 M formaldehyde concentration, selective formation of DHA (above 80 glc%) was obtained at the early stage of the reaction. The scheme for the formation of DHA in the formose reaction in the presence of vitamin B1 was also proposed.
  • Kyoji Furuta, Masaharu Ishiguro, Ryuichi Haruta, Nobuo Ikeda, Hisashi ...
    1984 Volume 57 Issue 10 Pages 2768-2776
    Published: 1984
    Released: June 27, 2006
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    The propargyltitanium reagents derived from 1-alkylpropyne condensed with aldehydes to give α-allenyl alcohol regioselectively, while the allenyltitanium reagents generated from 1-alky1-1-butyne derivatives gave threo-β-acetylenic alcohols with high regio- and stereoselectivities. The course of the reaction was determined by the substitution pattern of starting alkynes. The similar reactions of metallated 1,3-bis(trialkylsilyl)propyne or (trialkylsilyl)acetonitrile with aldehydes were also investigated.
  • Hiroaki Hiraoka, Kyoji Furuta, Nobuo Ikeda, Hisashi Yamamoto
    1984 Volume 57 Issue 10 Pages 2777-2780
    Published: 1984
    Released: June 27, 2006
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    The naturally occurring antibiotics asperlin and related fungal metabolites containing a 5,6-dihydro-2-pyrone moiety have been synthesized stereoselectively. The propargyltitanium reagent derived from 1-trimethylsilyl-3-(tetrahydropyranyloxy)propyne condensed with crotonaldehyde affords the corresponding erythro alcohol as the major product, which is converted to (±)-asperlin and the related three stereoisomers in seven steps.
  • Kyoji Furuta, Yoshihiko Ikeda, Noriyuki Meguriya, Nobuo Ikeda, Hisashi ...
    1984 Volume 57 Issue 10 Pages 2781-2790
    Published: 1984
    Released: June 27, 2006
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    [3-(Ethylthio)allyl]titanium reagent generated easily from allyl ethyl sulfides condensed with aldehydes to give erythro-β-hydroxy sulfides in highly regio- and stereoselective manner. In contrast, crotyl ethyl sulfide reacted with aldehydes affording δ-hydroxy vinyl sulfide exclusively. The substitution pattern of the starting sulfide can have a pronounced effect on the selectivity in this condensation reaction. erythro-β-Hydroxy sulfide obtained was transformed stereoselectively to the trans-vinyloxirane or 1,3-alkadiene.
  • Masaru Ohsaku, Takehiro Ichiishi, Akira Imamura, Michiro Hayashi
    1984 Volume 57 Issue 10 Pages 2791-2796
    Published: 1984
    Released: June 27, 2006
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    Ab initio self-consistent field MO calculations were performed on EtSH and EtOH, and the optimized geometries were obtained by the use of the STO-3G and STO-3G* basis sets. It was found that ab initio MO calculations reproduced the observed geometries of these molecules sufficiently well. The variation in the observed bond angle, α(CCX) (X=S and O), from the trans to the gauche rotamers, which was observed by means of microwave spectroscopy, was very reasonably reproduced from the results of these calculations. The total energy calculated gives a reasonable explanation of the stability between the rotational isomers.
  • Nobuo Nishino, Satoshi Morimoto, Masao Nakamura
    1984 Volume 57 Issue 10 Pages 2797-2801
    Published: 1984
    Released: June 27, 2006
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    This paper proposes a method by means of which the heat of solution at an infinite dilution of an organic compound in water, directly measured by means of calorimetry at a given temperature, is extended over a wide range of temperatures by the use of a phase diagram with water. The heat of solution at an infinite dilution in water over a temperature range from 290 to 350 K, which is estimated by this method for some alkanols and alkanoic acids, increases with a rise in the temperature and has a transition temperature from the exothermic region to the endothermic region which is close to the minimum dissolution temperature in the solubility curve in water for each substance. The increase in the heat of solution might be due to the breakdown of the iceberg formed around the alkyl group. The difference between the partial molar heat capacity at an infinite dilution and the molar heat capacity at the pure state, ΔScp\overset\ominus2, has its maximum at a certain temperature. The higher homolog shows a sharper curve with a lower maximum temperature. The curve of ΔScp\overset\ominus2vs. the temperature for 2- or 3-alkanol corresponds to that for the lower 1-alkanol. These facts reveal that a polar group, such as OH and COOH, would preferentially break the weaker structure of the iceberg within its breaking sphere, which structure should break down at a lower temperature.
  • Shin-ichi Fukada, Ryuichi Ikeda, Daiyu Nakamura
    1984 Volume 57 Issue 10 Pages 2802-2808
    Published: 1984
    Released: June 27, 2006
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    The temperature dependences of the 1H NMR spin-lattice relaxation time and of the second moment of 1H NMR absorptions in the temperature ranges of 90–400 K and 77–456 K, respectively, were studied for butylammonium bromide and its N-deuterated analog. There are three known crystalline phases in butylammonium bromide as a result of two phase transitions which are confirmed by the present differential thermal analysis (DTA) experiments. The transition temperatures determined in this study are 200 and 249 K for butylammonium bromide. In the low temperature phase of this salt, CH3 groups perform the C3 reorientation with a relatively low activation energy of 11.0 kJ mol−1. The asymmetric T1 curves observed suggest the existence of some kind of disorder in the crystal structure of this phase. In the intermediate phase, the C3 reorientation of NH3+ groups and the 180 ° flip motion of butylammonium chains are activated with the activation energies of 23 and 14 kJ mol−1, respectively. The present NMR results for the high temperature phase indicate the occurrence of the conformational melting of the cation chains. The mechanism of the phase transitions is discussed.
  • Ken-ichi Machida, Michio Enyo, Keisuke Oguro, Masanori Nakane
    1984 Volume 57 Issue 10 Pages 2809-2815
    Published: 1984
    Released: June 27, 2006
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    Hydrogen evolution reaction on a series of hydrogen absorbing Ni–V alloys, viz. Ni2V, NiV, and NiV3, before and after pretreatments with aq HF was studied in 1 M NaOH (1 M=1 mol dm−3) at 288–333 K by a galvanostatic overpotential transient technique. Results are related with the surface characteristics revealed by XPS techniques. It is concluded that the Ni in the Ni–V alloys is mainly responsible for their electrochemical properties and that the reaction proceeds via the Volmer-Tafel reaction route with mixed rate-determining characteristics: The activation heats are 7.7, 6.8, and kcal mol−1 (1 cal=4.184 J) for two elementary steps, Volmer and Tafel, and the overall reaction, respectively. The electrocatalytic activity of the Ni–V alloys, particularly NiV3, is drastically enhanced through the treatment with aq HF, and this is in parallel with the formation of porous Ni layers on their surface, namely the increase of the effective surface area. Potentiality of the alloys for water electrolysis cathode materials is indicated by a higher electrocatalytic activities of the Ni–V alloys over ordinary Raney nickel electrodes. Hydrogen absorbability of the alloys was also investigated: NiV3 stored hydrogen up to [H]/[M]=≤0.3 after a cathodic polarization at about −400 mV hydrogen overpotential, but that in Ni2V or NiV was far smaller.
  • Akira Kai
    1984 Volume 57 Issue 10 Pages 2816-2819
    Published: 1984
    Released: June 27, 2006
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    The influence of the culture conditions, such as the temperature of incubation and the pH of the culture medium, on the fibrillation of cellulose gels produced by Acetobacter xylinum was studied by means of electron microscopy. The incubation temperature did not show any influence on the fibrillation of cellulose gels as long as it was in the range between 10 to 28 °C. However, in the incubation at 5 °C the fibrillation occurred very slowly. When incubation was carried out at 5 °C, the fibril produced by the 5 °C incubation maintained an amorphous state for about 3h, and the microscopic fibrils appeared in the fibril only after incubation for 12h. However, the width of the microscopic fibril was not influenced by the temperature of incubation. The pH of the medium influenced the linear growth rate of a fibril. The rate increased with an increase in the pH, reached the maximum at pH 6.8, and decreased at higher pHs. The fibrillation occurred more rapidly at a constant temperature as the linear growth rate was lowered, but the width of a microscopic fibril was not influenced by the pH of the medium, just as it was not influenced by the temperature.
  • Kazuo Ito, Yutaka Tamaura, Takashi Katsura
    1984 Volume 57 Issue 10 Pages 2820-2023
    Published: 1984
    Released: June 27, 2006
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    The reaction of γ-FeOOH with the metal (Cd(II), Mg(II), or Zn(II)) and Fe(II) ions in solution gave the metal ion-bearing ferrites without oxidation. The ferrites obtained were the stoichiometric Mg(II)- and Zn(II)-bearing ferrites [Mg0.27Fe2.73O4.00 (pH 10.6), Zn0.38Fe2.61O4.00 (pH 10.5)] at pH 7.5–11.4, and the nonstoichiometric Cd(II)-bearing ferrites [Cd0.19Fe2.68O4.00 (pH 10.2)] at pH 7.5–10.5 (25 °C). The Cd(II)- and Mg(II)-ion content in the ferrites increases with an increase in the reaction pH, but the Zn(II)-ion content is almost constant at pH 7.5–10.5. This pH dependence of the metal-ion content in the ferrites agrees with that of the fractional adsorption of these metals on γ-FeOOH. This suggests that only the adsorbed metal ions are incorporated into the ferrites. The pH dependence of these metal-ion contents in the air-oxidation reaction is also similar to that in the transformation reaction from γ-FeOOH. This transformation reaction seems to be one process in the air-oxidation reaction.
  • Seiko Ito, Yoshiko Yano
    1984 Volume 57 Issue 10 Pages 2824-2828
    Published: 1984
    Released: June 27, 2006
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    The analysis of linewidth and shift data of the nitrogen-14 magnetic resonance gave the following activation parameters for the exchange reaction of pyridine (py) on CoA2(py)2 (A=acac, tfa, and tta) and Ni(acac)2(py)2 with a pyridine molecule as bulk solvent: ΔH\ eweq=41.4, 51.1, 48.3, and 47.2 kJ mol−1, ΔS\ eweq=18, 17, 3, and 10 JK−1 mol−1, and k1 (298K)=2.9×106, 5.3×104, 2.9×104, and 1.3×105 s−1. Here acac=acetylacetonate, tfa=trifluoroacetylacetonate and tta=thenoyltrifluoroacetonate. The electron-withdrawing power of substituent groups on the β-diketonate rings was correlated with more favorable activation of the exchange, that is, the stronger electron withdrawal causes less dissociative activation. This explains qualitatively even the negative ΔS\ eweq values observed for similar pyridine exchange in the cases of Co(hfa)2(py)2 (hfa=hexafluoroacetylacetonate) and Ni(tta)2(py)2.
  • Yoshinori Ihara, Ryokichi Tsuchiya
    1984 Volume 57 Issue 10 Pages 2829-2831
    Published: 1984
    Released: June 27, 2006
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    The following ten nickel(II) complexes with meso- or dl-1,2-diphenyl-1,2-ethanediamine (abbreviated as meso-stien and dl-stien, respectively) were prepared, and their thermal behavior was investigated in the solid phase: [Ni(meso-stien)2]X2 (X=Cl, Br, I, NO3, or ClO4), [Ni(dl-stien)2]X2 (X=I or ClO4), and [Ni(H2O)2(dl-stien)2]X2 (X=Cl, Br, or NO3). The square planar bis(dl-stien) complex chloride, bromide, and nitrate obtained by thermal dehydration of their respective octahedral diaqua complexes were found by various techniques to be transformed, upon further heating, to the octahedral diacido bis(dl-stien) complexes. The complexes containing dl-stien have a stronger tendency to show such structural transformations than those containing meso-stien. The reason for this difference is discussed.
  • Shuzo Tokunaga
    1984 Volume 57 Issue 10 Pages 2832-2834
    Published: 1984
    Released: June 27, 2006
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    For the reduction of Cu2+ ions with Ca–Si alloy in aqueous solutions, the following elementary reactions were postulated:
    Ca0+Cu2+=Ca2++Cu0, (1)
    Ca0+2H2O=Ca2++H2+2OH, (2)
    Si0+2Cu2++3H2O=H2SiO3+2Cu0+4H+, (3)
    Si0+3H2O=H2SiO3+2H2. (4)
    From these reactions, amounts of SiIV species were estimated by using those of H2 and increments of H+ ions. Total equivalents of the reduction products showed good agreement with those of the oxidation products, indicating the validity of the elementary reactions. The remained problems of the stoichiometric disagreement and the phenomenon of pH decrease indicated in Part II could be solved by using these elementary reactions. At the beginning of the reaction, a small amount of Cu+ ions formed. Decomposition of water occurred subsequently to the Cu2+ reduction. A contribution of Si0 to the reaction became greater than that of Ca0 at higher Cu2+ concentrations than ca. 10 matom dm−3. Thus, it proved that Si0 in the alloy exhibits a great reducing effect.
  • Yoshihisa Yamamoto
    1984 Volume 57 Issue 10 Pages 2835-2838
    Published: 1984
    Released: June 27, 2006
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    The reactions of methylenetriphenylarsorane, (C6H5)3As=CH2 (L), with ZnCl2 or HgCl2 in the mole ratio 2:1 yield new monomeric compounds of bis(methylenetriphenylarsorane)metal dichloride, [(C6H5)3AsCH2–M–CH2As(C6H5)3]Cl2. The reactions of L with BeCl2 or MgCl2 in the mole ratio 2:2 yield dimeric trigonal compounds of di-μ-chloro-bis[(methylenetriphenylarsorane)metal] dichloride, (Remark: Graphics omitted.). The reactions of L with AlCl3 or InCl3 in the mole ratio 4:2 yield dimeric tetrahedral compounds of di-μ-chloro-bis[bis(methylenetriphenylarsorane)metal] tetrachloride, (Remark: Graphics omitted.). The reactions of L with (C6H5)3MCl (M: Sn and Pb) in the mole ratio 1:1 yield new monomeric compounds of (methylenetriphenylarsorane)triphenyl-metal chloride, [(C6H5)3AsCH2–M(C6H5)3]Cl. They are thermally stable complexes and their properties are compared with those of the methylenetriphenylphosphorane metal compounds.
  • Hiroshi Nakamura, Tsukasa Yoshida, Masaaki Todoko, Keihei Ueno, Makoto ...
    1984 Volume 57 Issue 10 Pages 2839-2846
    Published: 1984
    Released: June 27, 2006
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    Seven chelating agents were synthesized. The complexation properties of these reagents with divalent metals (Cu2+, Co2+, Ni2+, Zn2+) were investigated in dioxane–water (75% dioxane, 25% water), and the complex formation constants were compared with those of 8-quinolinol as a reference chelating agent. These sulfonamidoquinoline reagents formed ML and ML2 type complexes, and the order of complex stabilities followed Irving-Williams’ order except for 2-methyl substituted derivatives. With 2-methyl derivatives, Ni2+ complexes were less stable than Co2+ complexes. Structural characteristics of sulfonamides as chelating agent were discussed in detail.
  • Hiromichi Yamada, Kaoru Takahashi, Yukio Fujii, Masateru Mizuta
    1984 Volume 57 Issue 10 Pages 2847-2851
    Published: 1984
    Released: June 27, 2006
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    The extraction of copper(II) with decanoic acid in some ketone solvents was carried out at 25 °C and at 0.1 mol/dm3 (NaClO4) aqueous ionic strength. Organic solvents used are 2-pentanone, 3-pentanone, 2-hexanone, 4-methyl-2-pentanone, 5-methyl-2-hexanone, and 2-octanone. For all solvents, the extracted species are CuA2, CuA2HA, Cu2A4, and Cu2A4(HA)2 (HA: decanoic acid). The dimerization and adduct formation of copper(II) decanoates in each organic phase can be formulated as:
    CuA2+HA\oversetKad,monomer\ ightleftharpoonsCuA2HA,
    Cu2A4+2HA\oversetβad,dimer\ ightleftharpoonsCu2A4(HA)2,
    2CuA2\oversetKdim–1\ ightleftharpoonsCu2A4,
    2CuA2HA\oversetKdim–2\ ightleftharpoonsCu2A4(HA)2.
    The solvent effects on the dimerization of copper(II) decanoate can be interpreted in terms of the regular solution theory. It was proved that the number of solvent molecules liberated in the formation of the dimeric copper(II) decanoate in ketones was less than that in alcohols.
  • Kazuaki Yamanari, Norimatsu Takeshita, Yoichi Shimura
    1984 Volume 57 Issue 10 Pages 2852-2858
    Published: 1984
    Released: June 27, 2006
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    Several (diamine)(2,9-dimethyl-4,7-diazadecane-2,9-dithiolato)cobalt(III) complexes, [Co(SNNS)(diamine)]+ (diamine=1,2-ethanediamine and (R,R)-1,2-cyclohexanediamine), were prepared and characterized by the visible-UV absorption, circular dichroism(CD), and 13C NMR spectra. The above SNNS quadridentate ligand gave only the cis-β geometrical isomer, which was chromatographically separated into two diastereomers owing to the configurations of chiral nitrogen atoms. All the thiolato and the corresponding sulfinato complexes exhibited two CD bands of opposite signs in the Co(σ*)←S(σ) ligand-to-metal charge transfer band region. The sign pattern was found to be in connection with the absolute configurations of these complexes.
  • Masato Nishizawa, Toshiro Yokoyama, Tetsuo Kimura, Toshishige M. Suzuk ...
    1984 Volume 57 Issue 10 Pages 2859-2862
    Published: 1984
    Released: June 27, 2006
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    Styrene–divinylbenzene copolymers containing –N(CH2CH2OH)2, –N(CH2CO2H)2, and –N(CH2PO(OH)2)2 moieties have been synthesized and applied to the selective adsorption of molybdenum and/or vanadium from aqueous solution. The equilibrium adsorption capacity vs. pH correlation and exchange kinetics of the resins for MoVI and VV have been studied. The resin containing bis(2-hydroxyethyl)amino group is particularly effective for the selective recovery of MoVI and/or VV by column operation due to its high adsorption capacity and faster exchange rate, whereas other resins required much longer time to attain adsorption equilibrium. The bis(2-hydroxyethyl)amino resin was used for the selective recovery of molybdenum from an acid-leaching solution of waste desulfurization catalyst.
  • Noriko Seki, Hiroyuki Ohno, Eishun Tsuchida, Shigeru Sasakawa
    1984 Volume 57 Issue 10 Pages 2863-2866
    Published: 1984
    Released: June 27, 2006
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    Human erythrocyte ghosts were taken into fragments by sonication. The average radius of the fragmented ghosts gradually decreased with the sonication time. The fragmented ghosts were obtained as spheres and reached to about 0.1 μm. In spite of the change in radius, their membrane fluidity was the same as that of the unsonicated ghost membrane. The [meso-α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato]iron(III)-mono (1-dodecyl-2-methylimidazole) complex was incorporated into the hydrophobic region of the fragmented ghost membrane. This hybrid showed a semistable oxygen adduct in pH 7.0 phosphate buffer solution.
  • Yoshihisa Watanabe, Yasushi Tsuji, Tatsuya Ohsumi, Ryo Takeuchi
    1984 Volume 57 Issue 10 Pages 2867-2870
    Published: 1984
    Released: June 27, 2006
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    Nitroarenes were transformed into the corresponding aminoarenes in high yields at 80 °C with carbon monoxide (an initial pressure 30–60 kg cm−2) and water in the presence of a catalytic amount of a platinum catalyst. The platinum catalyst was combined with tin(IV) chloride, triphenylphosphine and triethylarnine. This combination was essential for the high catalytic activity.
  • Katsuhiro Kawashiro, Shiro Morimoto, Hideyuki Yoshida
    1984 Volume 57 Issue 10 Pages 2871-2878
    Published: 1984
    Released: June 27, 2006
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    Trimethylsilylation of eight iminodicarboxylic acids (IDCAs) with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) or N,O-bis(trimethylsilyl)acetamide was studied under various reaction conditions. The IDCAs include iminodiacetic acid (1), 2- and 3-(carboxymethylamino)propionic acids (2 and 3), 2,2′-, 2,3′-, and 3,3′-iminodipropionic acids (46), N-methyliminodiacetic acid (7), and nitrilotriacetic acid (8). For 16, both bis- and tris(trimethylsilyl) (TMS) derivatives were formed under usual silylating conditions, although the proportion of amounts of the two derivatives varied depending on reaction conditions. This double derivatization was due to the steric hindrance of N-substituent group. However, under mild silylating conditions (BSTFA alone, 120 °C, 30 min), 16 yielded only the di-TMS derivatives. Upon electron impact at 20 eV, both the di- and tri-TMS derivatives showed simple spectra with a molecular (M+) ion and M −15 (loss of CH3). The α,α′-IDCAs (1, 2, 4, 7, and 8) are characterized by fragments M −43 (loss of CH3 and CO) and M −117 (loss of COOTMS) (base peak). On the other hand, the β,β′-IDCA (6) is characterized by fragments M −57 (loss of CH3, CH2, and CO) and prominent M −131 (loss of CH2COOTMS). The α,β′-IDCAs (3 and 5) exhibit both the fragments characteristic of α,α′- and β,β′-IDCAs, M −43, M −57, M −117, and M −131. However, base beaks are usually the fragment M −117 and not M −131.
  • Seiji Shinkai, Kazuyoshi Shigematsu, Yoshihiro Honda, Osamu Manabe
    1984 Volume 57 Issue 10 Pages 2879-2884
    Published: 1984
    Released: June 27, 2006
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    Photoresponsive crown ethers with heavy metal affinity were synthesized: They are the NS2O crowns bound to photofunctional azobenzene at 4,4′-positions via X(CH2 or CO) (1(X=CH2) and 1(X CO), respectively). They efficiently extracted heavy metal ions from aqueous phase to organic(dichloromethane) phase. The continuous variation method established that both trans-1 and photoisomerized cis-1 bind two Cu(II) ions forming 1:1 metal/NS2O crown complexes. The trans-1(X=CH2)·Cu(I)2 complex was irreversibly oxidized by O2 to the Cu(II)2 complex, whereas the cis-1(X=CH2)·Cu(I)2 complex bound O2 in a partly reversible manner like Osborn’s complex. Thus, a photoinduced change in the Cu(I)·····Cu(I) interatomic distance is responsible for the stability of the O2 complex. These results show that the extraction of heavy metal ions and the O2-complexation can be controlled by light with the mediation of photoresponsive NS2O crown ethers.
  • Masami Ishibashi, Shin Yoshimura, Takahiko Tsuyuki, Takeyoshi Takahash ...
    1984 Volume 57 Issue 10 Pages 2885-2892
    Published: 1984
    Released: June 27, 2006
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    Four new quassinoids, shinjulactones F, I, J, and K were isolated from Ailanthus altissima SWINGLE. The structure of shinjulactone F was established to be 1α,11-epoxy-1β,20-dihydroxy-5βH-picrasa-3,9(11)-diene-2,12,16-trione by X-ray diffraction analysis. The structures of shinjulactones I, J, and K were determined to be 11α-acetoxy-2α, 12α-dihydroxypicrasane-1,16-dione, 1β,12β-dihydroxypicrasane-2,11,16-trione, and 12α-acetoxy-2α,11α-dihydroxypicrasane-1,16-dione, respectively, by spectral and chemical means.
  • Makoto Ojika, Hiroki Kuyama, Haruki Niwa, Kiyoyuki Yamada
    1984 Volume 57 Issue 10 Pages 2893-2896
    Published: 1984
    Released: June 27, 2006
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    The structure of miyaginin previously reported as p-vinylphenyl O-D-xylosyl-(1→6)-D-glucoside without stereochemical assignment of two glycosidic linkages was reinvestigated by spectral and chemical means and shown to be revised as p-allylphenyl O-β-D-xylopyranosyl-(1→6)-β-D-glucopyranoside (p-allylphenyl β-primeveroside). In order to confirm the revised structure, an unambiguous synthesis of miyaginin was performed.
  • Ryoichi Ando, Tomoo Sugawara, Makoto Shimizu, Isao Kuwajima
    1984 Volume 57 Issue 10 Pages 2897-2904
    Published: 1984
    Released: June 27, 2006
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    In the reactions with enolate anions, organoselenium moieties of aryl vinyl selenoxides and selenones have exhibited two important roles, e.g., activation of C=C bonds for conjugate addition reaction and behaviors as excellent leaving groups. Owing to such characteristic features, ketone enolates react with p-chlorophenyl vinyl selenoxide to afford the corresponding cyclopropyl ketones through an initial conjugate addition followed by substitution processes. On the other hand, use of vinyl selenones usually gives much better results with anionic species of active methylene compounds. Vinyl selenones bearing hydroxyl, ketone, and ester groups can also be employed equally well for this type of transformation.
  • Michio Kobayashi, Toshihiko Hoshi, Jun Okubo, Hiroshi Hiratsuka, Toshi ...
    1984 Volume 57 Issue 10 Pages 2905-2909
    Published: 1984
    Released: June 27, 2006
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    The electronic absorption spectrum of diphenylhexatriyne has been divided into two components polarized along the long and the short molecular axes by means of dichroism analysis using the stretched-polymer-film technique; i.e., a reduced polarization spectrum has been obtained. This reduced polarization spectrum can be explained by a modified PPP calculation including the interaction between mutually perpendicular π and π′ systems in the conjugated system. It has been clarified that the relative intensities of the first and second bands of diphenylhexatriyne reflect the magnitude of interaction between mutually perpendicular π and π′ systems, which is quite great. The magnitude of the electron-repulsion integral between π and π′ electrons is estimated to be about 20–30 per cent of that between ordinary π (or π′) electrons.
  • Yoshinobu Shiokawa, Shin Suzuki
    1984 Volume 57 Issue 10 Pages 2910-2913
    Published: 1984
    Released: June 27, 2006
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    The polarographic reduction of Gd, Yb, and Cf was investigated. It was found that the M(III)→Hg(M) reduction process in an aqueous solution, that cannot be detected by dc polarography, can be detected by radiopolarography. The polarographic behavior of Gd, Eu, Yb, and Cf in the presence of 1,4,7,10,13,16-hexaoxacyclooctadecane(18-crown-6) suggests that Cf(III) is reduced in two steps to Hg(Cf) in an aqueous solution.
  • Makoto Watanabe, Yoshio Morii, Shoji Sato
    1984 Volume 57 Issue 10 Pages 2914-2918
    Published: 1984
    Released: June 27, 2006
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    Calcium phosphoramidate monohydrate was made by adding an aqueous calcium chloride solution to an aqueous potassium hydrogenphosphoramidate solution at pH 9.0–9.5 below 5 °C. The product was stable at room temperature, but it was decomposed by heating. When the product was heated at 150 °C in air, the phosphoramidate decomposed to produce anhydrous calcium phosphoramide and also ortho- and diphosphates. The elimination of ammonia from amino groups to form a P–N(H)–P linkage was not observed at this temperature. The phosphoramidate decomposed in air to form ortho-, imidodi-, di-, and a small amount of higher polyphosphates at a temperature higher than 150 °C. Imidodiphosphate was decomposed to diphosphate by moisture in air. β-Calcium diphosphate was formed by heating the phosphoramidate at a temperature higher than 750 °C in air. When the phosphoramidate was heated in dried N2, it showed the same thermal reaction as that in air below 250 °C, while the amount of imidodiphosphate in the thermal product was larger than that in air at a temperature higher than 400 °C.
  • Reiko Nakamura, Kiyofumi Nagai, Mamoru Shimoi, Akira Ouchi
    1984 Volume 57 Issue 10 Pages 2919-2924
    Published: 1984
    Released: June 27, 2006
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    The new complexes indicated in the title have been synthesized, and the crystal and molecular structure of the neodymium(III) complex has been determined by the X-ray diffraction method. The crystal is monoclinic, with the space group C2/c, Z=16, a=28.887(4), b=28.913(5), c=24.814(5)Å, β=106.72(1)°. The final R value for 7761 reflections is 0.066. The central neodymium(III) atom of the complex is octa-coordinated and is in a dodecahedron geometry; three O,O′-diisopropyl dithiophosphato ligands, chelating by both of the sulfur atoms, span the two m edges of a trapezium as well as one a edge of the other trapezium, and two oxygen atoms of both the benzamide ligate at both tips of the base edge of the latter trapezium. The solid and the acetonitrile solution of the europium(III) complex are orange in color, and they show a charge-transfer band in their near-ultraviolet absorption spectra.
  • Yasuhisa Ikeda, Hiroshi Tomiyasu, Hiroshi Fukutomi
    1984 Volume 57 Issue 10 Pages 2925-2929
    Published: 1984
    Released: June 27, 2006
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    The exchange reaction of N,N-dimethylformamide(dmf) in [UO2(acac)2dmf](acac=acetylacetonato) has been studied by the NMR line-broadening method in CD3COCD3 and CD2Cl2. In CD3COCD3, the rate of dmf exchange is independent of the free DMF concentration. The rate constants(s−1) at 25 °C and activation parameters ΔH\ eweq(kJ mol−1) and ΔS\ eweq(JK−1 mol−1) are 1.19×103, 42.0±1.3, and −45.8±5.5, respectively. In CD2Cl2, the exchange rate depends on the free DMF concentration. The exchange rate constant (kex) is expressed by kex=k1+k2[DMF], where k1(25 °C)=1.90×102s−1, ΔH\ eweq=32.8±1.7 kJ mol−1, and ΔS\ eweq=−92.0±5.9 JK−1 mol−1, and k2 (25 °C)=5.66×103 M−1s−1(1M=1 mol dm−3), ΔH\ eweq=37.0±2.1 kJ mol−1, and ΔS\ eweq=−49.6±8.8 JK−1 mol−1. The D and I mechanisms are proposed for the dmf exchange in [UO2(acac)2 dmf].
  • Kazuhiko Nakayama, Takashi Komorita, Yoichi Shimura
    1984 Volume 57 Issue 10 Pages 2930-2941
    Published: 1984
    Released: June 27, 2006
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    Mixed-ligand [Pd(N)n(O)4–n]-type complexes constituting a long systematic series (n=0–4) were synthesized. Ammonia, ethylenediamine, rac-propylenediamine, trimethylenediamine, glycinate, β-alaninate, acetate, oxalate, and malonate were employed as ligands. Their magnetic circular dichroism (MCD) and electronic absorption spectra were discussed together with the CD spectra of the corresponding optically active complexes. The results strongly suggest that the dispersion of MCD observed in the spin-allowed d-d region is primarily a composite of B terms. Moreover, the MCD in the charge transfer region was found to be qualitatively additive with respect to contributions by the constituent ligands. From a detailed examination of the spin-allowed d-d absorption bands, it is noted that the substitution of an N,O-ligand for an N,N-ligand largely affects neither the band area nor band width whereas that of an O,O-ligand for an N,O-ligand does.
  • Noboru Oyama, Hisao Yamamoto, Takeo Ohsaka, Masao Kaneko
    1984 Volume 57 Issue 10 Pages 2942-2946
    Published: 1984
    Released: June 27, 2006
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    Photoelectrochemical reaction of the Fe(CN)52− complex (PVP[Fe(CN)52−]n) coordinated to the unprotonated poly(4-vinylpyridine) (PVP) film on a graphite electrode was examined in an aqueous solution. It was found that the carbon electrode coated with the PVP[Fe(CN)52−]n generates the long-time responses of the photocurrents under irradiation of visible light and that the mechanism of its photochemical reaction is different from that for the photochemical reaction of [Fe(CN)6]3− in a bulk solution, where the dissociation reaction of [Fe(CN)6]3− to its aqua ion occurs.
  • Yuichi Fujimura, Minoru Arai, Nobuaki Nakashima, Keitaro Yoshihara
    1984 Volume 57 Issue 10 Pages 2947-2953
    Published: 1984
    Released: June 27, 2006
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    Expressions for the intensity of the time-resolved absorption (TRA) by molecules after radiationless transition have been derived. It is assumed that a non-equilibrium vibronic distribution is realized after the radiationless transition and relaxes to the equilibrium one. Two types of non-equilibrium distributions, Poisson distribution and canonical distribution with temperature higher than that of the heat bath are taken into account. The theory developed is applied to the TRA spectra (S3←S0) of benzene after the internal conversion S2\ ightsquigarrowS0 (N. Nakashima and K. Yoshihara, J. Chem. Phys. 79, 2727, (1983)). It is shown that the expression for the intensity in the Sulzer-Wieland model is involved in the expression derived using the canonical distribution.
  • Masataka Yokoyama, Kouichi Tsuji, Tsuneo Imamoto
    1984 Volume 57 Issue 10 Pages 2954-2956
    Published: 1984
    Released: June 27, 2006
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    Some 5-substituted pyrazoles and pyrimethamine were prepared from 3-methylthio-1-phenyl-4-phenylsulfonyl-2-buten-1-one (5a) or (E)-1-p-chlorophenyl-1-cyano-2-methylthio-3-phenylsulfonylpropene (6b) which could be easily synthesized from methyl phenyl sulfone.
  • Hiroki Kondo, Katsunori Takaki, Ryoichi Kuroki, Akihiro Tada, Kunihiro ...
    1984 Volume 57 Issue 10 Pages 2957-2961
    Published: 1984
    Released: June 27, 2006
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    The following two fluorescent peptides were prepared as substrates of the cyclic AMP-dependent protein kinase reaction: Leu–Arg–Arg–Ala–Ser–Leu–X; 1 (X= 2-(dansylamino)ethylamino or DAE) and 2 (X=4-methyl-2-oxo-7-chromenylamino or MCA). Both peptides were phosphorylated by ATP and the catalytic subunit of cyclidAMP-dependent protein kinase from bovine heart in a stoichiometric manner. Phosphorylation of peptide 1 is accompanied by a 10% increase in the fluorescence intensity at 550 nm. This enables one to assay peptide phosphorylation by fluorescence spectroscopy. The kinetic parameters obtained by this and the conventional phosphocellulose paper method for this phosphorylation were the following: Km 7.8 μM and Vmax 35 μmol·min−1·mg−1 for 1, and Km 7.4μM and Vmax 16 μmol·min−1·mg−1 for 2.
  • Akira Sekiya, Teruo Umemoto
    1984 Volume 57 Issue 10 Pages 2962-2964
    Published: 1984
    Released: June 27, 2006
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    The reaction of trifluoronitrosomethane 1 with arenesulfonohydrazides resulted in the formation of N-trifluoromethyl-N-hydroxyarenesulfonamides 3 which were characterized by spectral and elemental analyses. It showed a sharp contrast to the reaction of 1 with acyl- or carbamoylhydrazines, which afforded the corresponding trifluoromethylazo compounds. As an alternative route, 3 could be synthesized by the reaction of 1 with arenesulfinic acids or their salts. The sulfonamides 3 were converted to the corresponding methyl ethers or tosylates.
  • Mitsuhiro Fukuda, Shigeru Kunugi
    1984 Volume 57 Issue 10 Pages 2965-2970
    Published: 1984
    Released: June 27, 2006
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    Steady state and presteady state kinetic analyses were performed for thermolysin-catalyzed hydrolysis of chromophoric tripeptide substrates with free carboxyl terminal. The pH dependence of kcat showed fairly higher pKa (\simeq7) than that of the second-order rate parameter(kcatKm)(\simeq5) and the pH-dependence of Km resembled that of Ki for N-blocked dipeptidyl inhibitor observed before (S. Kunugi et al., Eur. J. Biochem. 124, 157 (1982)). These findings indicated that the reaction with this type of substrate involves a nonproductive binding mode. In a presteady state kinetic study by stopped-flow method, a burst process of 10–20 ms order was observed before the linear steady state at a relatively low pH and temperature. This process showed moderate pH dependence. Considering these experimental results coupled with those accumulated so far on this enzyme, a unified mechanism including a nonproductive binding and an isomerization process in prior to the cleavage of the peptide bond was proposed for the dipeptidyl carboxypeptidase activity of this enzyme.
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