bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Properties of Cobalt(III)–1,2-Bis(dimethylphosphino)ethane (dmpe) Complexes of the [Co(L)(dmpe)2]n+ Type
Authors: Ohishi Tomoji , Kashiwabara Kazuo , Fujita Junnosuke 
Published: July 2006

Abstract
Seven new cobalt(III)–phosphine complexes of the type [Co(L)(dmpe)2]n+ were prepared from trans-[Co(Cl or Br)2(dmpe)2]+, where dmpe denotes (CH3)2PCH2CH2P(CH3)2, and L is C2O42−, NH2CH2COO−(gly), NH2CH(CH3)COO−(ala), (C2H5)2NCS2−(dtc), (NCS−)2, (NCO−)2, or (CN−)2. Reactions of cis-[CoCl2(dmpe)2]+ with X− (X−=CN−, NCS−, and NCO−) yielded only trans-[CoX2(dmpe)2]+. Qualitative stabilities of the complexes containing a bidentate ligand in aqueous solution were found to decrease in the order L=CH(CH3CO)2−(acac), C2O42−, dtc&gt;CO32−&gt;&gt;gly, ala&gt;NH2CH2CH2NH2(en); the complexes containing O or S donor atoms are thermally more stable than those containing an amino donor group. The d–d absorption bands of the complexes were assigned by comparing the spectra with those of related Co(III)–phosphine and -en complexes. The IR and visible absorption spectra of the NCS− and NCO− complexes indicate an N coordination mode of these ambidentate ligands.
Preparation and Stereochemistry of Cobalt(III) Complexes with Ethylenediamine-N-acetate and 3-Azapentane-1,5-diamine or 3-Methyl-3-azapentane-1,5-diamine
Authors: Yasui Takaji , Shikiji Toshie , Koine Norio , Ama Tomoharu , Kawaguchi Hiroshi 
Published: July 2006

Abstract
Four geometrical isomers possible in each of [Co(edma)(dien)]2+ and [Co(edma)(mdien)]2+, where edma, dien, and mdien denote ethylenediamine-N-acetate, 3-azapentane-1,5-diamine, and 3-methyl-3-azapentane-1,5-diamine respectively, and facial isomer of [Co(edma)(NH3)3]2+ were prepared and resolved into optically active isomers by a column-chromatographic method. The structural assignments of these geometrical isomers were carried out on the basis of the absorption, 1H NMR, and 13C NMR spectral data. The absolute configurations of the optically active isomers containing facially coordinated edma were determined by 1H NMR measurements of the glycinate-ring methylene (–CHD–) of edma stereospecifically deuterated in a weak basic D2O. The relationship between the absolute configurations and the CD spectral behaviors of these isomers is also discussed.
A Formylcarbonium Ion Synthon. Synthesis of 3-Thio-Substituted 2-Amino Acids and Thio-Substituted Enamines from 2-Acyloxyacrylonitriles
Authors: Oku Akira , Hori-ie Naofumi , Harada Toshiro 
Published: July 2006

Abstract
The utilization of 2-acyloxy-3 -phenylthiopropionitriles (2) which were prepared by the Michael addition of thiophenol to 2-acyloxyacrylonitriles (CH2=C(CN)OCOR), as a formylcarbonium ion synthon, was demonstrated by the transformation of 2 into S-phenylcysteine and 2-phenylthio enamines.
Ethylene Glycol from Synthesis Gas by Homogeneous Ruthenium and Ruthenium–Rhodium Catalysts
Authors: Kiso Yoshihisa , Saeki Kenji 
Published: July 2006

Abstract
In the formation of ethylene glycol from synthesis gas, amines (especially imidazole and its derivatives) enhanced the catalytic activity of a ruthenium carbonyl mixed with alkali metal halides. A rhodium carbonyl complex further promoted the activity and selectivity of a ruthenium–alkali metal halide-imidazole catalyst.
Photoadducts of 4,6-Dimethyl- and 4-Methoxy-6-methyl-2-pyrones with Chloroethylenes and Their Dehydrochlorination
Authors: Shimo Tetsuro , Somekawa Kenichi , Wakikawa Yusuke , Uemura Hisako , Tsuge Otohiko , Imada Kiyohisa , Tanabe Kimiko 
Published: July 2006

Abstract
Sensitized photoreactions of 2-pyrones with chloroethylenes gave two kinds of [2+2]cycloadducts, 2-oxabicyclo[4.2.0]oct-4-en-3-ones (4, 8) and across the C3–C4 double bond in 2-pyrone, benzene derivatives, and/or cyclobutanecarboxylic acids: Their relative yields greatly depended upon the nature of the reactants. The dehydrochlorination of the cycloadducts 4 and 8 across the C5–C6 double bonds in the pyrones with triethylamine in ethanol gave 5-ethenyl-2-pyrones, whose structures were previously incorrectly assigned as oxocinones, via a symmetry-allowed ring opening of 2-oxabicyclo[4.2.0]octa-4,6-dien-3-ones. Some 5-ethenyl-2-pyrones possessing a chlorinated ethenyl group finally affords 5-ethynyl-2-pyrones by an anti-elimination of hydrogen chloride. The X-ray crystallographic analyses of 5-ethenyl- and 5-ethynyl-2-pyrones are also described.
The Effects of Catalysts on the Mean Structure of Solvent-Refined Coal in Coal Liquefaction
Authors: Chiba Koji , Tagaya Hideyuki , Sato Shimio , Ohgi Shinya 
Published: July 2006

Abstract
The effects of MoO3, Fe2O3, or SnO on the conversion and the solvent-refined coal (SRC) yield of Taiheiyo coal were small, whereas their effects on the structure of SRC were large. SRC was separated into four fractions by successive extraction in order to clarify the differences in SRC’s among the catalysts. The formation of SnO2 after the liquefaction was confirmed. It was considered that the oxygen-abstraction ability and the radicalstabilization ability of SnO prevented the retrogressive reaction of coal, SRC, and model compounds. MoO3 and Fe2O3 have a higher ability to hydrogenate and accelerate the hydrocracking of coal and coal-model compounds than does SnO, but their ability to suppress the retrogressive reaction producing heavier compounds is small.
Preparation, 1,3-Dipolar Cycloaddition, and Thermal and Photochemical Reactions of 3,5-exo- and 3,5-endo-7-Methylene-4-azatetracyclo[4.2.1.0.2,803,5]nona-9-ones
Authors: Kanomata Nobuhiro , Kobayashi Tadashi , Uetake Takashi , Okada Shuji , Nitta Makoto 
Published: July 2006

Abstract
The 1,3-Dipolar cycloaddition of phenyl azide with 1,3,5-trimethyl-6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-one occurred onto the endocyclic double bond to give the exo- and endo-adducts (7 and 8) in a similar ratio. Upon photoirradiation, 7 and 8 eliminated a nitrogen molecule to give 3,5-exo- and 3,5-endo-1,3,6-trimethyl-7-methylene-4-azatetracyclo[4.2.1.0.2,803,5]nona-9-ones (9 and 10) in good yields. The 1,3-Dipolar cycloaddition of 2,4,6-trimethylbenzonitrile oxide with 9 and 10 occurred onto the exocyclic double bond to give two stereoisomers in each case. The stereoselectivity of the reactions is discussed on the basis of the stereoelectronic factor of the aziridine ring. The thermal reaction of 9 and 10 as well as photoirradiation of 9 caused a simple C–N bond cleavage of the aziridine ring. However, photoirradiation of 10 or its dimethyl analogue caused an unusual skeletal rearrangement resulting in the formation of 9-methylene-6-phenyl-6-azatricyclo[3.3.1.02,8]nona-3-en-7-one ring system. Mechanistic pathways of the rearrangement were postulated.
Formulation of Enthalpy, Entropy, and Volume Changes Accompanying Association Reaction in Solution in Terms of Molecular Distribution Functions
Authors: Yoshimura Yosuke , Nakahara Masaru 
Published: July 2006

Abstract
The equilibrium constant of the chemical reaction in solution is formulated by means of the distribution function at the semiclassical level. The equivalence of the present expression and the traditional one that is based on the standard chemical affinity is proved. The changes of the thermodynamic quantities (enthalpy, entropy, and volume) at constasnt temperature and pressure are expressed on the basis of the present formulation. They are composed of the following three terms: (i) the internal change, (ii) the translational change, and (iii) the solvation change. Each term is evaluated for the dimerization of nitrogen dioxide. It is shown that the volume change is a good measure for the solvation change because it does not contain the internal change. Since the solvation change is explicitly expressed by means of the radial distribution function and its temperature or pressure derivative in an explicit manner, it is useful for discussing the solvent effect on the chemical reaction from the point of view of the liquid structure.
Design and Synthesis of Amphiphilic Basic Peptides with Antibacterial Activity and Their Interaction with Model Membrane
Authors: Mihara Hisakazu , Kanmera Tatsuhiko , Yoshida Mutsuo , Lee Sannamu , Aoyagi Haruhiko , Kato Tetsuo , Izumiya Nobuo 
Published: July 2006

Abstract
Twelve peptides having 4 to 6 basic amino acid residues in the hydrophobic amino acid sequence were designed and synthesized by the solution method to find peptides with potential activity against Gram-positive and -negative bacteria. CD study of the peptides demonstrated that they formed α-helical structures in the presence of phospholipid liposomes consequently to have amphiphilic property along the axis of helix. The peptides also induced the leakage of the dye carboxyfluorescein from phospholipid vesicles, indicating that the peptides possess the ability to perturb the membrane structure. These peptides showed antibacterial activity against Gram-positive bacteria, and some of them were also active against Gram-negative bacteria. Relationships between the structure and antibacterial activity of the synthetic peptides were discussed.
Chlorination of Acyclic β-Diketones. Formation and Stability of β-Chloro-β,γ-unsaturated Ketones
Authors: Sugita Toshio , Ito Hiroshi , Nakajima Akihiko , Sunami Motoshi , Kawakatsu Atsushi , Suama Masakazu , Ichikawa Katsuhiko 
Published: July 2006

Abstract
Chlorination of acyclic β-diketones with triphenylphosphine–carbon tetrachloride and the other chlorinating reagents predominantly afforded β-chloro-β,γ-unsaturated ketones except the cases of the terminal alkyl group of the diketones was methyl or t-butyl. In these reactions, the isomerization of the β-chloro-α,β-unsaturated ketones to the β,γ-unsaturated isomers was involved; the isomerization was achieved by triphenylphosphine–carbon tetrachloride as well as by some acid catalysts.
(α-Ethoxyvinyl)tributyltin; An Efficient Reagent for the Nucleophilic Acetylation of Organic Halides via Palladium Catalysis
Authors: Kosugi Masanori , Sumiya Takashi , Obara Yukimasa , Suzuki Motohiro , Sano Hiroshi , Migita Toshihiko 
Published: July 2006

Abstract
(α-Ethoxyvinyl)tributyltin acts as a masked acetylating agent in the palladium catalyzed reaction with various organic halides, such as aryl bromides, vinyl bromides, benzyl chloride, and allyl chloride, giving, after hydrolysis of the resulting reaction mixture, good yields of the corresponding ketone product.
The Ring Opening Reaction of Cyclopolysilanes, (R2Si)n (n=3–6), with Iodine. A Kinetic Study
Authors: Watanabe Hamao , Shimoyama Hiromi , Muraoka Tsutomu , Kougo Yuichi , Kato Motohiko , Nagai Yoichiro 
Published: July 2006

Abstract
Reactions of a series of peralkylcyclopolysilanes with iodine were found to proceed via second-order kinetics. Rate constants show that, in general, the smaller rings react faster than larger rings. Values of the activation parameters, Ea and ΔG\eweq, decreased with the decreasing ring size and are parallel with those of the oxidation potentials and of the lowest transition energies.
Laser Flash Photolysis of Azocumenes. Direct Observation of Stepwise Decomposition
Authors: Sumiyoshi Takashi , Kamachi Mikiharu , Kuwae Yoko , Schnabel Wolfram 
Published: July 2006

Abstract
The mechanism of the decomposition of α,α′-azocumene and 2,2′-di-p-tolyl-2,2′-azopropane was studied by means of laser flash photolysis (λ=347 nm) and the optical absorption of 1-methyl-1-phenylethyl (α-cumyl) and α-cumyldiazenyl radicals was observed. The α-cumyl radicals were formed in two modes, a fast mode occurring during the flash and a slow mode after the flash. The ratio of the optical densities pertaining to the two modes depended on the absorbed dose rate. The higher the absorbed dose per flash, the more dominant was the fast mode. The transient band at λ=285 nm which decayed simultaneously with the grow- in of the α-cumyl radicals was assigned to α-cumyldiazenyl radicals. The experimental results strongly suggested the occurrence of the stepwise decomposition mechanism. The dose rate dependent kinetics of the slow formation process was explained in terms of the competition between the unimolecular decomposition and the dimerization of α-cumyldiazenyl radicals. The rate constants of the decomposition and the dimerization were estimated to be 1.1×105 s−1 and 5×109 M−1 s−1, respectively.
Reduction of Aromatic Nitro Compounds and Thioketones with Sodium Telluride under Aprotic Conditions
Authors: Suzuki Hitomi , Manabe Hajime , Kawaguchi Takashi , Inouye Masahiko 
Published: July 2006

Abstract
Sodium telluride, prepared by heating tellurium and sodium hydride in a 1:2 molar ratio in dry N,N-dimethylformamide, reduces aromatic nitro compounds to azo compounds and thioketones to hydrocarbons under mild conditions.
Electrogenerated Acid-Assisted Preparation of Ethers from Aldehydes and Ketones
Authors: Torii Sigeru , Takagishi Sadahito , Inokuchi Tsutomu , Okumoto Hiroshi 
Published: July 2006

Abstract
Symmetrical and unsymmetrical ethers are prepared from carbonyl compounds and alkoxytrimethylsilanes in the presence of hydrosilane by using an electrogenerated acid catalyst.
The Crystal Structure of a New Charge-Transfer Complex of Hexamethylenetetrathiafulvalene with Triiodide, HMTTF·I3
Authors: Honda Kazumasa , Goto Midori , Kurahashi Masayasu , Anzai Hiroyuki , Tokumoto Madoka , Bando Hiroshi , Ishiguro Takehiko 
Published: July 2006

Abstract
The crystal structure of bis(trimethylene)tetrathiafulvalenium triiodide (hexamethylenetetrathiafulvalenium triiodide) has been determined. The space group is P\bar1, with a=7.973(2), b=11.849(3), c=14.412(4) Å, α=82.86(2), β=89.13(3), γ=95.85(2)°, and Z=3. The crystal has intermolecular S…S contacts 3.36 and 3.37 Å shorter than the van der Waals distance of 3.7 Å.
The ESR Detection of N Atoms in Methane–Air Combustion Flames Doped with Nitrogen Compounds
Authors: Taniguchi Masayuki , Noda Shoji , Yoshida Hiroshi 
Published: July 2006

Abstract
The ESR spectra of nitrogen atoms were detected for the first time in the combustion flames of methane doped with ammonia. The dependence of the N-atom concentration on the flame conditions was examined. The results were then discussed with reference to the models of the reduction of NH3, leading to the NO formation.
Photochromism of Viologen Crystals
Authors: Kamogawa Hiroyoshi , Suzuki Tsuyoshi 
Published: July 2006

Abstract
Some viologen crystals bearing a p-toluenesulfonate anion as a counter ion were shown to exhibit reversible photoreductions (photochromism) either in air or under vacuum, whereas in a poly(N-vinyl-2-pyrrolidone) matrix all investigated viologens indicated reversible photocolor developments. Amphoteric ions such as 1,1′-bis(3-sulfonatopropyl)-4,4′-bipyridinium also developed colors with high stabilities.
Fast Cis-Trans Isomerization of Square-Planar Bis(diethyl sulfide)platinum(II) Complexes. Reaction of cis-Dichlorobis(diethylsulfide)platinum(II) with Mesityllithium
Authors: Tobita Hiromi , Habazaki Hiroki , Ogino Hiroshi 
Published: July 2006

Abstract
Reaction of cis-[PtCl2(SEt2)2] with a slight excess of mesityllithium in benzene–ether mixture afforded trans-[PtCl(Mes)(SEt2)2] (Mes=2,4,6-trimethylphenyl; SEt2=diethyl sulfide) as a major product. When mesityllithium reagent containing lithium bromide was used, trans-[PtBr(Mes)(SEt2)2] was obtained. Acceleration of cis–trans isomerization in the presence of mesityllithium was observed.
Stepwise Oxidation of the Heteroatoms in O-Protected Pyridoxine-Like Pyridinophane Containing Thio Groups in the Intramolecular Bridge Chain
Authors: Ando Makoto , Kuzuhara Hiroyoshi 
Published: July 2006

Abstract
Racemic 14-Hydroxy-15-hydroxymethyl-O,O′-isopropylidene-2,8-dithia[9](2,5)pyridinophane, a model compound of our chiral pyridoxamine analogs, was oxidized under various conditions in order to examine the reactivities of the sulfur and the nitrogen atoms. Various degree of oxidized compounds, from monoxide to pentaoxide, including the desired S,S,S′,S′-tetraoxide, were obtained.
Electrochemical Reduction of exo-5-Acetyl-endo-6-trichloromethylbicyclo[2.2.1]hept-2-ene
Authors: Tsuboi Sadao , Ishiguro Yasuhiro , Takeda Akira 
Published: July 2006

Abstract
Electrochemical reduction of exo-5-acetyl-endo-6-trichloromethylbicyclo[2.2.1]hept-2-ene (2) using a mercury cathode gave chemoselectively either the corresponding monochloromethyl or dichloromethyl derivatives in high yields by selecting supporting electrolyte. The reduction of 2 using a lead cathode gave 2-acetyl-3-methylbicyclo[2.2.1]hepta-2,5-diene and cis-1-(4-vinyl-2-cyclopentenyl)-2-propanone together with by-products.
Hydrates of Organic Compounds. XI. Determination of the Melting Point and Hydration Numbers of the Clathrate-Like Hydrate of Tetrabutylammonium Chloride by Differential Scanning Calorimetry
Authors: Nakayama Haruo 
Published: July 2006

Abstract
A thermal analytic method using a differential scanning calorimeter has been applied to binary mixtures of water with tetrabutylammonium chloride. It has been found that this method can give the same results concerning the melting point (15.2 °C) and hydration numbers (around 30) of the clathrate-like hydrate of tetrabutylammonium chloride as those determined phase-diagrammatically. The apparent enthalpy of fusion of water which forms hydrogen-bonded water lattice in the clathrate-like hydrate has been observed to be 5.47 kJ mol−1, which is comparable with 5.20 kJ mol−1 determined by the direct calorimetric measurements of enthalpy of solution of the hydrate in water. It has been concluded that the proposed method can be applicable to many similar types of systems, including systems forming a hydrate which decomposes incongruently.
Surface Characterization of Silica Modified with Aminosilane Compounds
Authors: Kondo Seiichi , Ishikawa Tatsuo , Yamagami Naoki , Yoshioka Kiyotaka , Nakahara Yoshiko 
Published: July 2006

Abstract
Adsorption behaviors, IR spectroscopy and surface electric properties were studied on the surfaces of well-defined mesoporous silica gels modified with triethoxy(3-aminopropyl)silane (TAS) and [3-(dimethylamino)propyl]diethoxymethylsilane (DDS). Surface free silanol groups react with ethoxyl groups of these compounds rigidly. Isoelectric points and points of zero charge of modified silicas shift from pH 3 of pure material to alkali, but DDS-modified silica gels dissolve themselves in aqueous phase because of their strong alkali environment.
81Br Nuclear Quadrupole Resonance of Cs2ZnBr4 and Crystal Stability of Compounds of A2MX4 Type
Authors: Nakayama Hirokazu , Nakamura Nobuo , Chihara Hideaki 
Published: July 2006

Abstract
The temperature dependences of 81Br nuclear quadrupole resonance frequencies and quadrupolar relaxation times of Cs2ZnBr4 were measured. The librational motion of [ZnBr4]2− about the Zn–Br axis parallel to the a axis in the crystal is more active than those about the other axes. The reason why this compound shows no phase transition can be accounted for by the molecular packing, especially the packing of [ZnBr4]2− along the a axis. General examination of the relative size of cation/anion in the class of compounds of A2MX4 type led to a criterion which may be used to rationalize existence and absence of a phase transition.
Is Accurate X-Ray Analysis Worthwhile?
Authors: Dunitz Jack D 
Published: July 2006

Abstract
Following a brief introduction to X-ray analysis, three areas are discussed where accurate measurements can lead to results of interest to chemistry. These areas are: (a) molecular geometry, (b) molecular motions in the solid state, (c) experimental electron density distributions. As the technical possibilities for accurate X-ray analysis improve, important developments in all three areas can be expected.
Compensation Effects in the Activation Parameters for the Homolytic Dissociation of Transition Metal–Alkyl Bonds
Authors: Halpern Jack 
Published: July 2006

Abstract
Determining the activation enthalpies of the homolytic dissociation of transition metal–alkyl bonds constitutes one of the most useful methods of deducing such bond dissociation energies. For several series of organocobalt compounds it has been found that trends of increasing enthalpies of activation for homolytic cobalt–carbon bond dissociation (i.e., of cobalt–carbon bond dissociation energies) are accompanied by partially compensating trends of increasingly positive entropies of activation. Evidence is advanced that these compensation effects are genuine. A suggested explanation is that, with increasing endothermicity of the bond dissociation process, the transition state becomes more “product-like,” i.e., further along the path to dissociation.
Syntheses and Dynamic Behavior of Chiral Heptalenes
Authors: Hafner Klaus , Knaup Günter L , Lindner Hans Jörg 
Published: July 2006

Abstract
Cycloaddition reactions of azulenes with dimethyl acetylenedicarboxylate afford an excellent access to a large variety of substituted dimethyl 1,2-heptalenedicarboxylates. These can be converted into various methylheptalenes, which proved to be remarkably stable. This allowed for the first time a separation of the bond shift isomers as well as an optical resolution of derivatives of this axial chiral 12π-electron system. Kinetic studies of bond shifting and ring inversion provide information on the transition states of these dynamic processes.
Antioxidants
Authors: Scott Gerald 
Published: July 2006

Abstract
Antioxidants can be classified by the way in which they interfere with the process of autoxidation. Two main types can be identified; the chain-breaking antioxidants which either reduce the alkylperoxyl radical or oxidise the alkyl radical and the preventive antioxidants which either retard the breakdown of hydroperoxides (metal deactivators, UV absorbers) or destroy them by non-radical mechanisms. Synergism results from the complementary action of antioxidants when used together. Recent studies of antioxidant mechanisms have led to the discovery of “stable” redox systems which are able to catalytically scavenge alkyl and alkylperoxyl radicals in competition with the normal reactions of these species in autoxidation. The physical behaviour (solubility, volatility etc.) of antioxidants can dominate their behaviour under certain conditions and the development of polymer-bound antioxidants is believed to be a solution to antioxidant migration and loss.
Insertion of Carbon–Heteroatom Multiple Bonds into Bis(η5-cyclopentadienyl)titanacyclobutenes
Authors: Meinhart James Douglas , Grubbs Robert Howard 
Published: July 2006

Abstract
Titanacyclobutenes that are readily produced by the reaction of Tebbe reagent with disubstituted acetylenes react with a variety of heteroatom multiple bonds. The reaction with aldehydes and ketones is particularly clean and has been studied mechanistically. The aldehyde or ketone carbonyl oxygen coordinates to the titanium center in a preequilibrium step before ring expansion to the product metallaoxacyclohexenes.
Removal of Phosphates from Aqueous Solution by Active Charcoal Electrode
Authors: Ichinose Masao , Yasuoka Takashi , Mitsuzawa Shunmei , Sasaki Tsunetaka 
Published: July 2006

Abstract
The electrolytic removal of phosphoric acid and mono-, di-, and tripotassium phosphates from aqueous solution was attemped using improved active charcoal electrodes which proved more effective in removing these electrolytes than the previous one. The degree of removal of phosphoric acid and phosphates exceeded 90% after 80 min’s electrolysis, tending to 100% after sufficient time of electrolysis. The mechanism of removal of phosphoric acid and potassium phosphates was confirmed to be the entrapment and concentration of these substances as potassium hydroxide and phosphoric acid in the pores of the active charcoal. The processes of removal of phosphoric acid and phosphates were found to be complicated due to hydrogen and hydroxide ions formed by the dissociation of phosphoric acid and hydrolysis of phosphates respectively which explained the initial rate of removal of these substances decreasing in the order of phosphoric acid through potassium dihydrogen- to tripotassium phosphate. Regeneration of active charcoal electrode was further inferred.