bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Spectrofluorometric Determination of 9,10-Phenanthrenequinone
Authors: Tachibana Masaki , Hayakawa Makoto , Furusawa Motohisa 
Published: July 2006

Abstract
9,10-Phenanthrenequinone (9,10-PQ) reacts with guanidine in an alkaline medium to form 2-amino-1H-phenanthro[9,10-d]imidazole. The reaction can be used for the fluorometric determination of 9,10-PQ, since the reaction product is fluorescent in an acidic solution. A dimethyl sulfoxide-methanol mixture is suitable as the solvent. A sample solution was allowed to stand for 15 min at room temperature after the additions of guanidine hydrochloride and sodium methoxide solutions, followed by the addition of hydrochloric acid. After the solution had been allowed to stand for 20 min, the fluorescence intensity of the solution was measured at 403 nm with excitation at 363 nm. The fluorescence intensity was stable for at least 8 h. The determination limit of 9,10-PQ was 50 ng.
The Stereochemistry of the Photochemical Rearrangement of 1-Substituted 1a,7b-Dihydro-1H-cyclopropa[a]naphthalenes under Sensitized Conditions
Authors: Kato Masahiko , Kobayashi Hisako , Yamamoto Hiroyuki , Seto Koji , Ito Satoru , Miwa Toshio 
Published: July 2006

Abstract
The photolysis of 1-substituted 1a,7b-dihydro-1H-cyclopropa[a] naphthalenes in the presence of Michler’s ketone leads principally to 5-substituted 5H-benzocycloheptenes as primary products via a stepwise mechanism. The reaction proceeds smoothly with inversion of the migrating carbon if there is no steric hindrance, but it proceeds predominantly with retention if the inversion course is severely suppressed by steric hindrance. The marked difference in the exo-endo ratio of the secondary photocyclization products depending on the irradiation conditions was also recognized for 1-methoxycarbonylmethyl derivative.
Formation of Intramolecular Hydrogen Bond in Hydroxy-substituted Nitroxide Radicals as Evidenced by Electron Spin Resonance
Authors: Kotake Yashige , Kuwata Keiji 
Published: July 2006

Abstract
The nature of the intramolecular hydrogen bond in hydroxysubstituted nitroxide radicals was examined. The hydroxysubstituted radical was produced by the spin trapping reaction of hydroxyalkyl radicals with α-phenyl-N-t-butylnitrone. The magnitude of the hyperfine splitting caused by β-hydrogen of the radical is strongly dependent on the composition of the solvent, which is attributed to the formation of the intramolecular hydrogen bond. The equilibrium constant of the intramolecular hydrogen bond in an aprotic solvent was determined by observing the magnitude of the hyperfine splitting of β-hydrogen as a function of the amount of added methanol. Based on the temperature dependence of the equilibrium constant, the standard entropy and the standard enthalpy of the formation of the hydrogen-bonded chelate ring was estimated. The same method of analysis was applied to the system of diastereomeric nitroxide and the difference of the internal energy of the chelate ring in the isomers was detected. Moreover, the difference was utilized to separate the ESR spectra of the diastereomers.
Synthesis, Electrical Resistivities, and Electronic Reflection Spectra of Alkaline-earth Metal Cation–TCNQ–Crown Ether Complexes
Authors: Matsumoto Tsuruyoshi , Nogami Takashi , Tanaka Hidekazu , Mikawa Hiroshi 
Published: July 2006

Abstract
Two types of alkaline-earth metal cation–TCNQ–crown ether complexes were synthesized: one is the simple salt, expressed as [M2+(TCNQ−)2]m(crown ether)n and the other is the complex salt expressed as [M2+(TCNQ−)2]m(TCNQ)n(crown ether)i. The electrical resistivities of the complexes were measured for compacted samples and single crystals. The resistivities of the simple salts were greater than 105 Ω cm, so they are much less conductive than the original TCNQ salts, M2+(TCNQ−)2. Most of the complex salts were more conductive than the original TCNQ salts, with the resistivities of 4–103 Ω cm.
Conformational Characteristics of Poly(vinylnaphthalene)s from Energy Contour Map
Authors: Seki Kazuhiko , Imamura Yoshio 
Published: July 2006

Abstract
In poly(1-vinylnaphthalene)(P1VN) and poly(2-vinylnaphthalene)(P2VN), conformational energies of meso and racemic dyads were computed as functions of skeletal bond and side group rotations (0°(o) or 180°(π)). The calculation was carried out according to the truncation procedure proposed by D.Y.Yoon. The backbones in P1VN and P2VN were limited to just two rotational states, trans (t) and gauche (g) conformation. The steric interactions involving the bulky naphthyl group precluded \barg conformation; a similar situation occurs in polystyrene. Numerical results suggested these conclusions: the excimer forming site conformations for P1VN were meso : tt(ππ) and racemic : tt(ππ) states, and for P2VN were meso : tt(ππ), tt(oo), tt(oπ), and tt(πo) states. These conformations could also be correlated to the dual emissions observed in P1VN and P2VN.
Kinetic Isotope Effects in the H+C3H6→C3H7 Reaction
Authors: Watanabe Toshifumi , Kyogoku Takeshi , Tsunashima Shigeru , Sato Shin , Nagase Shigeru 
Published: July 2006

Abstract
The absolute rate constants of the addition of H and D atoms to propylene-d0 and -d6 have been measured by means of the pulse radiolysis-resonance absorption technique over the temperature range of 200–500 K. The rate constants obtained were well expressed by these Arrhenius equations: k(H+C3H6)=(3.00±0.38)exp[−(1612±66)⁄RT], k(H+C3D6)=(2.55±0.57)exp[−(1509±128)⁄RT], k(D+C3H6)=(1.99±0.05)exp[−(1550±15)⁄RT], and k(D+C3D6)=(2.20±0.27)exp[−(1587±67)⁄RT] in units of 10−11 cm3 molecule−1 s−1. The unit of activation energy is cal mol−1. Practically no isotope effects attributable to the difference between C3H6 and C3D6 could be observed. This is similar to the kinetic isotope effects previously observed in the rate constants of the addition of H and D atoms to isotopic ethylenes. The theoretical rate constants of the above reactions have been calculated by the conventional activated complex theory using the potential energy surface drawn by the ab initio method; however, no agreement with regard to the isotope effects could be obtained between experiment and theory because of the difference between C3H6 and C3D6. This also is similar to the isotope effects found in the H+C2H4→C2H5 reaction.
Studies on Mixed Chelates. XIII. Formation and Electronic Spectra of 5-Coordinated Mixed Copper(II) Chelates Containing N-Alkylated Ethylenediamine, Acetylacetonate, and Halide Anions
Authors: Fukuda Yutaka , Kimura Hiroko , Sone Kozo 
Published: July 2006

Abstract
The visible absorption spectra of three new mixed chelates of copper(II), Cu(acac)(tmen)X (acac=acetylacetonate ion, tmen=N,N,N′,N′-tetramethylethylenediamine, and X−=Cl−, Br−, or I−) were studied in various organic solvents. The \ ildeνmax values of their d-d bands depend strongly on the nature of the solvent, similarly to the pseudohalide complexes reported in the preceding paper. These data show the existence of the equilibrium:
[Cu(acac)(tmen)X]\ightleftharpoons[Cu(acac)(tmen)]++X−
(5-coordinated) (4-coordinated, with axial solvation)
in such solutions, which is shifted to the right hand side with increase of the solvent polarity and with decrease of the coordination ability of the X− anion, i.e., in the order Cl−→Br−→I−.
The Mechanism of the Hydrolysis of Polyphosphates. VI. The Effect of Cations on the Hydrolysis of cyclo-Tri-and cyclo-Tetraphosphates
Authors: Watanabe Makoto 
Published: July 2006

Abstract
The effect of cations on the rate of the hydrolysis of cyclo-tri- and cyclo-tetraphosphates was studied by adding metal chlorides to aqueous solutions of the ring phosphates. The concentrations of the phosphates and metal chlorides were 0.025 mol dm−3 and 0.1 mol dm−3 respectively. Alkali-metal cations retarded the hydrolysis of both the cyclo-phosphates in acidic media and accelerated it in basic media. The following sequence of efficiency resulted:
Li+&gt;Na+&gt;K+.
Magnesium, calcium, and nickel(II) cations retarded the hydrolysis of the cyclo-phosphates in the pH range of 1.0–2.0 or 1.0–2.7, while they accelerated it in the pH regions higher than 2.7 or 3.5. A copper(II) ion retarded the hydrolysis at pH 1.0, and accelerated it in the pH ranges higher than 2.0. An aluminium ion highly accelerated the hydrolysis of both the ring phosphates at pH 1.0 and 2.0.
Kinetics of the Ligand Substitution Reactions of Tetrahedral Complexes [Co(NN)(hmpa)2]2+(NN=2,2′-Bipyridine, 4,4′-Dimethyl-2,2′-bipyridine, or 1,10-Phenanthroline) in Hexamethylphosphoric Triamide, Nitrobenzene, Acetone, 1,2-Dichloroethane, and Nitromethane
Authors: Abe Yuriko , Wada Goro 
Published: July 2006

Abstract
The substitution reaction rates of hexamethylphosphoric triamide (HMPA) for NN (NN=2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), or 1,10-phenanthroline (phen)) on tetrahedral complexes [Co(NN)(hmpa)2]2+ were determined spectrophotometrically in pure HMPA or in nitrobenzene, acetone, 1,2-dichloroethane, and nitromethane at various concentrations of HMPA, for the purpose of clarifying the reaction mechanism and the effect of the bulkiness of HMPA. The ligand substitution reaction on bpy and dmbpy complexes proceeds simply via a dissociative mechanism in nitrobenzene. In inert solvents other than nitrobenzene, it proceeds in parallel via two simultaneous paths of both dissociative and associative mechanisms. In the case of the phen complex, the reaction proceeds only by a dissociative mechanism in pure HMPA and in all the inert solvents used. The activation enthalpies and the activation entropies of the dissociative mechanism of bpy and dmbpy complexes were (80–90) kJ mol−1 and approximately zero J K−1 mol−1, respectively, in all the solvents used. Those for the phen complex were (86–101) kJ mol−1 and (−16–+36) J K−1 mol−1, respectively, while those of the associative mechanism for bpy and dmbpy complexes in all the solvents used except nitrobenzene were (50–65) kJ mol−1 and large negative values, respectively. Whether the substitution proceeds by the dissociative mechanism or by the associative one, both the steric and the solvent effects appear seriously, because HMPA is a bulky ligand and had a large dipole moment.
Pyrolytic Sulfurization Gas Chromatography. XIII. Simultaneous Determination of the Atomic Ratio between C, H, O, and N in a Metal Organic Chelate Compound
Authors: Hara Tadashi , Fujinaga Kaoru , Okui Fujio 
Published: July 2006

Abstract
In order to clarify the effect of the coexistent elements on the determination of the atomic ratio between C, H, O, and N by the pyrolytic sulfurization gas chromatography (PSGC), compounds containing 25 kinds of elements were investigated. Only 7 of these interfered the determination of the atomic ratio. Several organophosphorus, lithium-, and boron-containing compounds were also analyzed. The results obtained by the present work are summarized in the periodic table together with those from previous work.
Multiple Conformations and Conformational Change in the Acetonitrile of Cation-binding Cyclic Tetrapeptide, Cyclo[Gly–l-Cys(Bzl(OMe))–Sar–l-Pro]
Authors: Shimizu Toshimi , Tanaka Yoshio , Tsuda Keishiro 
Published: July 2006

Abstract
The conformations of the cyclic tetrapeptide, cyclo[Gly–l-Cys(Bzl(OMe))–Sar–l-Pro] (CGCSP), in solution, were studied by means of 1H-, 13C-nuclear magnetic resonance (NMR), and circular dichroism (CD). The CGCSP equilibrates among three conformers, M, m, and n, in acetonitrile, providing three sets of resonances for each proton in the 1H-NMR spectrum. An inspection of a CPK model indicated that the three structures were sterically allowed to occur by the cis-trans isomerism around the Cys-Sar and Sar-Pro peptide bond. The temperature dependence of the amide proton resonances in 1H-NMR suggested that one γ-turn (1←3 hydrogen bond from the Cys to the Pro) is present in the two conformers, M and m. Thus, the three conformations in acetonitrile were deduced from all of the spectral data. This cyclic tetrapeptide is capable of binding a monovalent cation, Li+, and divalent cations, Mg2+, Ca2+, and Ba2+. Its CD titration curves demonstrated that at least three types of complexes with Ca2+ and Ba2+ were formed. In contrast, Li+ and Mg2+ were shown to form the 1 : 1 complex with this pep tide. The NMR data suggest that the conformational change of the cyclic backbone takes place by changing the geometry of the peptide bonds around the Cys–Sar–Pro sequence on the addition of a metal cation.
The Photochemistry of the Host-Guest Complex. VII. The Photoreaction of Dicyanopyrazine Derivatives Having a Crown Ether Moiety
Authors: Tada Masaru , Hamazaki Hirohide , Hirano Hideki 
Published: July 2006

Abstract
The irradiation of 4′-(5,6-dicyano-2-pyrazinyl)benzo-15-crown-5 and 5,6-dicyano-2-(3,4-dimethoxyphenyl)pyrazine in the presence of a tertiary or secondary amine caused reductive decyanation to give 5-decyano derivatives, which in turn gave bis(decyano) derivatives on further irradiation. Free-energy changes upon single-electron transter from the amine to the excited state of dicyanopyrazine derivatives are exothermic for triethylamine and diethylamine, but endothermic for butylamine. The single-electron transfer was evidenced by the effect of the sodium ion on the quantum yields of the reaction products and the fluorescence quenching.
Synthesis of threo-3-Methylcysteine from Threonine
Authors: Wakamiya Tateaki , Shimbo Kuniaki , Shiba Tetsuo , Nakajima Kiichiro , Neya Masahiro , Okawa Kenji 
Published: July 2006

Abstract
threo-3-Methyl-d-cysteine as a moiety of β-methyllanthionine in the peptide antibiotic nisin was synthesized stereospecifically. The reaction of (2R,3R)-3-methyl-2-aziridinecarboxylic acid derivative prepared from d-threonine with thiobenzoic acid gave the β-mercapto α-amino acid derivative of the same configuration as the starting material. A stereochemistry of the product was retained as a result of double inversion mechanism through the reactions. Thus, we could prepare threo-3-methyl-d-cysteine, i.e., (2S,3S)-2-amino-3-mercaptobutanoic acid which is required for the synthetic study of nisin.
Brillouin Scattering and Ultrasonic Absorption Measurements of Chloroform–Eicosane Mixtures
Authors: Nomura Hiroyasu , Shimizu Hayao , Tanaka Yasuharu , Koda Shinobu , Okunishi Toshio , Kato Shigeo , Miyahara Yutaka 
Published: July 2006

Abstract
An apparatus for the accurate measurement of Brillouin scattering of liquids and solutions was constructed using a multi-pass Fabry-Perot interferometer. The Brillouin scattering spectra of chloroform–eicosane mixtures were obtained at various concentrations. The sound velocity dispersion curves of this system could be expressed by a single relaxation equation. With increasing concentration of eicosane, the relaxation frequency shifted to the higher frequency side, but the relaxation strength was independent of concentration. It is concluded that this relaxation was due to the vibrational-translational energy transfers of chloroform molecules due to the collisions between chloroform and eicosane molecules.
Structure of Tetra-μ-formatodiruthenium Bromide
Authors: Kimura Takashi , Sakurai Tosio , Shima Makoto , Togano Tadashi , Mukaida Masao , Nomura Terunosuke 
Published: July 2006

Abstract
X-Ray structural determination of Ru2(HCOO)4Br showed that the unit cell contains two crystallo-graphically independent formato bridged dinuclear units, Ru2(HCOO)4+, each of which is centrosymmetric. Two adjacent units are bridged by bromide ion to make infinity zigzag chains.
Homologation of Methyl Esters Catalyzed by Ruthenium–Cobalt Bimetallic Systems
Authors: Hidai Masanobu , Koyasu Yukio , Yokota Makoto , Orisaku Masami , Uchida Yasuzo 
Published: July 2006

Abstract
Reactions of methyl esters such as methyl acetate with synthesis gas have been investigated by use of the mixed clusters such as [Et4N][RuCo3(CO)12] and [Et4N][Ru3Co(CO)13] or a combination of Ru(acac)3 and Co2(CO)8 as catalyst and methyl iodide as promoter. In the homologation of methyl acetate, the catalytic activity for formation of ethyl acetate was much improved when both ruthenium and cobalt existed in the reaction system.
Chemical Systems Exhibiting Complicated Temporal Oscillations
Authors: Iwamoto Kazutoshi , Kawauchi Susumu , Sawada Kiyoshi , Sen\={o} Manabu 
Published: July 2006

Abstract
Two model systems exhibiting complicated oscillations were proposed and analyzed. One of them is a double oscillation system, which shows alternating oscillations of large and small amplitudes and the mechanism for appearance of the double oscillations is clarified. In the other system, either large or small amplitude oscillation appears depending on the parameter values, and the transition between the large and the small amplitude oscillation is very abrupt and sensitive to the change in external constraints.
A Potentiometric Study on Mixed Ligand Cadmium(II) Complexes with 2-Amino Carboxylic Acids
Authors: Matsui Haruo , Ohtaki Hitoshi 
Published: July 2006

Abstract
Formation constants of mixed ligand cadmium(II) complexes, CdLL′, were determined in aqueous solutions containing 3 mol dm−3 LiClO4 as a constant ionic medium at 25 °C by potentiometric titration, where the ligands HL and HL′ are 2-amino carboxylic acids such as glycine, α-alanine, 2-aminobutanoic acid, 2-aminopentanoic acid, and 2-aminohexanoic acid. Ten kinds of the mixed ligand cadmium(II) complexes were examined with the combination of five 2-amino carboxylic acids. The formation constant, βprs=[CdpLrLs′(2p−r−s)+]⁄([Cd2+]p×[L−]r[L′−]s), of the mixed ligand cadmium(II) complexes containing glycine as one of the ligands lie between those of the parent complexes, while the formation constants of the other complexes are larger than those of the parent complexes. No protonated mixed ligand complex has been observed. The small values of β111 of the Cd(gly)L complexes are due to the considerably small values of the first stepwise formation constants of the CdL+ complexes. On the other hand, the stepwise formation constants of the CdL+ complexes with glycinate ion are larger than the stepwise formation constants with 2-amino carboxylate ions and the second stepwise constant of the bis(glycinato)cadmium(II) complex. Interactions between the ligands through the central cadmium(II) ion are discussed. The b-values (b=log {(K110·K101)⁄(K120·K102)}, where K1rs denotes the stepwise formation constant of the complex CdLrL′s) of the mixed ligand cadmium(II) complexes containing glycinate ion as one of the components lie between 0.93 and 0.98, and are larger than those of the other complexes (b=0.83–0.90), the fact indicating that the mixed ligand glycinato complexes have larger inter-ligand interactions within the complexes than those within complexes containing other 2-amino carboxylate ions. The inter-ligand interaction may occur through the central cadmium ion within the complex.
NMR and CD Spectral Features of Thiaheterohelicenes. Effect of Intramolecular Overlap of Aromatic Rings
Authors: Yamada Koh-ichi , Tanaka Hisao , Nakagawa Hiroko , Ogashiwa Susumu , Kawazura Hiroshi 
Published: July 2006

Abstract
NMR and CD spectral features of a series of thiaheterohelicenes containing alternant thiophene and benzene rings were examined as associated with their helical structures. The terminal ring protons of the thiaheterohelicenes reflected the characteristics of intramolecular overlap of aromatic rings in 1H NMR spectra. With the progression of the helix a sudden chemical shift of the β proton in the end thiophene ring to the higher field occurred, in contrast to carbohelicenes in which the drift of the upfield shift of the corresponding terminal ring proton was gradually suppressed. The CD spectra of thiaheterohelicenes were quite different from those of carbohelicenes. The intensities of the α and β absorption bands weakened with the progressive annelation, whereas the intensity of the p absorption band gradually increased, accompanied by a successive increase in the anisotropy factor of the band. These facts suggest that the structures of thiaheterohelicenes differ from those of carbohelicenes in having a peculiar distortion of the helix.
Collins Oxidation of Methyl (+)-13β-Abiet-8-en-18-oate and Absolute Configuration of Suaveolic Acid
Authors: Matsumoto Takashi , Imai Sachihiko , Yuki Shuhei , Katayama Arata , Furutani Manabu 
Published: July 2006

Abstract
The oxidation of methyl (+)-13β-abiet-8-en-18-oate with Collins reagent yielded nine oxidation products. Their structures were elucidated on the basis of spectroscopic and chemical data to be methyl (−)-14-hydroxy-7-oxoabieta-8,11,13-trien-18-oate (1% yield), methyl (−)-11,14-dioxoabieta-8,12-dien-18-oate (1%), methyl (+)-11-oxo-13β-abiet-8-en-18-oate (18%), methyl (−)-8α,9α-epoxy-7-oxo-13β-abietan-18-oate (2%), methyl (+)-7-oxoabieta-8,11,13-trien-18-oate (2%), methyl (+)-11,14-dihydroxy-7-oxoabieta-8,11,13-trien-18-oate (2%), methyl (+)-7,11-dioxo-13β-abiet-8-en-18-oate (17%), methyl (+)-14-oxo-13β-abiet-8-en-18-oate (15) (4%), and methyl (+)-7-oxo-13β-abiet-8-en-18-oate (23%) respectively. It is noteworthy that oxygenation occurs not only at the C-7 and C-11 positions but also at the C-14 position. The oxygenated products obtained in this studies could be useful intermediates for the synthesis of the oxidized diterpenoids of abietane skeleton. To exemplify this, 15 was converted to methyl suaveolate and suaveolol. Hydrolysis of the former yielded suaveolic acid, thus confirming its absolute configuration to be 4R, 5R, 10S, 13S, and 14S.
Reaction of Haloazoxybenzenes with Sulfuric Acid
Authors: Shimao Ichiro , Fujimori Ken , Oae Shigeru 
Published: July 2006

Abstract
Treatment of 4,4′-dihaloazoxybenzenes with sulfuric acid afforded 4,4′-dihaloazobenzenes (6) as the major product and 5-halo-2-(p-halophenylazo)phenols, the Wallach rearrangement products as minor products, besides 2-halo-5-(p-halophenylazo)phenols, 2-halo-4-(p-halophenylazo)phenols, and 4-(p-halophenylazo)phenols as abnormal rearrangement products. The reaction of fluoro compound gave the azophenols (3a or 5a) in the best yields. However, the ratio of 3a to 5a was found to vary with the concentration of sulfuric acid. Treatment of 4-haloazoxybenzenes with sulfuric acid gave 4-(p-halophenylazo)phenols and 4-haloazobenzenes (13) as major products together with 2-(p-halophenylazo)phenols and 5-halo-2-(phenylazo)phenols as minor products. Yields of reduction products 6 and 13 increased as the halosubstituent became heavier in the following sequence: F→Cl→Br→I.
The Solvomercuration, Bromination, and Related Reactions of 1,5-Dimethyl-6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-one and Its Related Compounds
Authors: Nitta Makoto , Omata Akihiko , Sugiyama Hiroshi 
Published: July 2006

Abstract
The solvomercuration-demercuration reactions of 1,5-dimethyl-6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-one (1), its corresponding alcohol, and 5,8-dimethyl-9-methylenetricyclo[3.3.1.02,8]non-3-en-7-one (2) were investigated. In all cases, the solvent was stereospecifically incorporated on the exomethylene group, and the original tricyclic skeleton did not undergo rearrangement. Similarly, 1 and 2 underwent a stereospecific bromination on the exomethylene group by means of the reaction with pyridinium tribromide. These results suggest the stabilization of the formal cyclopropylcarbinyl cation intermediates by the adjacent acetoxymercury moiety or the bromine atom. On the other hand, the reaction of NBS–MeOH or NBS–H2O with 1 afforded an addition product on the exomethylene group, and 1,4-addition originated from the cleavage of the cyclopropane ring, while with 2 the reaction afforded only an addition product on the exomethylene group. The difference in this reaction mode is discussed on the basis of the solvent effect and the ring strain of 1.