bluuebunny/crossref_metadata_2025 huggingface dataset:
An ENDOR Study of Diphenyl Nitroxide and Its Methyl Derivatives, The Effect of the Methyl Substitution
Authors: Yamauchi Jun , Okada Keiichi , Deguchi Yasuo
Published: July 2006

The ENDOR spectra of diphenyl nitroxide (DPNO) and its monomethyl derivatives were observed in ethylbenzene at −70 °C. The agreement between the ESR and ENDOR data is generally good. The MO calculations, however, indicate a few disagreements in the case of the m- and o-methyl DPNO derivatives. The methyl substitution at the meta-position destroys the equivalency of all protons at the meta-positions, which are divided into two sets of equivalent proton groups of the same number. The ortho-substitution weakens the coplanarity of the two benzene rings and increases the number of the equivalent proton groups, which are fully resolved in the ENDOR spectrum. The steric hindrance is taken into account in the MO calculation, which can predict these slightly different coupling groups-again except for those in the meta-positions. A satisfactorily simulated spectrum of the o-methyl DPNO is obtained on the basis of the ENDOR data.
Time-Resolved Unimolecular Reactions of Pyridine Ions by Means of Trapped-Ion Mass Spectrometry
Authors: Arakawa Ryuichi , Yoshikawa Yozaburo
Published: July 2006

The electron-impact ionization-efficiency curves for the C5H5N+·→C4H4+·+HCN dissociation have been measured as a function of the ion-source-residence time by means of trapped-ion mass spectrometry (TIMS). The ionization-efficiency curves for residence times of 5 and 700 μs were fitted by QET calculation, assuming dissociation-rate models. A kinetic shift of 0.3 eV was observed from the time-dependent appearance energy measurements. The fragmentation of metastable ions was first sampled for the ion-source residence time of 0–100 μs. The preferable rate model was determined by the analysis of the ionization-efficiency curves and the metastable ion fragmentations. Time-resolved kinetic energy releases for pyridine and perdeuteriopyridine have been explained in terms of excess energy drop of metastable ions with their lifetime.
The Structure of the Cyclodextrin Complex. XIX. Crystal Structures of Hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin Complexes with (S)- and (R)-Mandelic Acid. Chiral Recognition through the Induced-Fit Conformational Change of the Macrocyclic Ring
Authors: Harata Kazuaki , Uekama Kaneto , Otagiri Masaki , Hirayama Fumitoshi
Published: July 2006

Hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin (methyl-α-CDx) forms crystalline inclusion complexes with (S)-mandelic acid (S-MA) and (R)-mandelic acid (R-MA). Both crystals are monoclinic, and the space group is P21 with cell dimensions: a=13.123(2), b=23.187(4), c=13.113(2) Å, β=107.19(1)° for the S-MA complex, a=11.624(2), b=23.739(4), c=13.786(2) Å, β=106.56(1)° for the R-MA complex. The structures were solved by inspection of a Patterson map and the R-map method, and refined by the block-diagonal least-squares method to the R-values of 0.087 for the S-MA complex and 0.055 for the R-MA complex. In the S-MA complex, the methyl-α-CDx molecule, which has a pseudo two-fold symmetry, loosely includes the phenyl group of S-MA. The hydroxyl and carboxyl groups of S-MA protrude from the O(2), O(3) side of the methyl-α-CDx cavity and form hydrogen bonds with water molecules located outside the host cavity. The methyl-α-CDx molecule in the R-MA complex tightly binds the R-MA molecule which is deeply inserted into the host cavity. The hydroxyl group of R-MA is hydrogen-bonded to an O(2) oxygen atom of host methyl-α-CDx. The comparison of the two structures suggests that the complex formation induces the conformational change of the host molecule to accommodate S-MA or R-MA more suitably within the cavity.
The Vaporization of the Various Trace Components from Aluminoborosilicate Glass
Authors: Itoh Noriko , Nakamura Tetsur\={o}
Published: July 2006

The simultaneous vaporization of dopants in aluminoborosilicate glass was investigated by means of mass spectrometry using a Knudsen cell. The detected chemical species were Na, K, Ni, Zn, Rb, Ag, Te, TeO2, and Cs in the temperature range of 650–800°C. Their vapor pressures were 10−6–10−4 Pa. The activation energy of vaporization was discussed in relation to the electrostatic force between the vaporizing specie and oxygen. However, lithium, alkali-earth metal elements, alomst all the transition metal elements (such as Fe, Cr, and Ru), and rare-earth metal elements were not detected in the vapor phase, though they were contained in the glass matrix.
The Solvent Extraction of Alkali and Alkaline Earth Metal Ions with Nonionic and Ionic Surfactants Having Poly(oxyethylene) Chain
Authors: Sakai Yukio , Shinmura Masahiro , Otsuka Hajime , Takagi Makoto
Published: July 2006

Extraction behavior of alkali and alkaline earth metal cations was investigated with a new extractant derived from polyethylene glycol mono[4-(1,1,3,3-tetramethylbutyl)phenyl]ether (Triton X-100; average number of oxyethylene group, 10) by introducing a phenolic(2-hydroxy-5-nitrobenzyl) group at the hydroxyl terminal of the polyethylene glycol chain. Alkali metal cations were extracted into 1,2-dichloroethane by forming 1:1 complex with the extractant. The overall extraction constant sequence was K+(10−9.15)>Rb+(10−9.26)>Cs+ (10−9.28)>Na+ (10−10.08)>Li+(10−10.36). The selectivity for K+, Na+, and Li+ was discussed by comparing the extraction behavior with a mixture of nonionic surfactant or dicyclohexano-18-crown-6 and a proton-dissociable lipophilic dye. For alkaline earth metal cations, the extractability decreased in the order Ba2+>Sr2+>Ca2+>>Mg2+. The metal extractability strongly depended on the nature of the anion in the aqueous phase.
Vapor-Phase Amination of Cyclohexanol over Silica-Supported Platinum Group Metal Catalysts
Authors: Hamada Hideaki , Kuwahara Yasushi , Sato Takahiro , Wakabayashi Katsuhiko
Published: July 2006

Vapor-phase amination of cyclohexanol with ammonia over silica-supported platinum and other platinum group metal (Ru, Rh, Pd, Ir) catalysts has been studied. Cyclohexylamine and aniline are the main products. Platinum is the most active metal, although there is not much difference in the activity between platinum and other metals. The reaction is suggested to proceed as follows. The first step, which is rate-determining, is the dehydrogenation of cyclohexanol to cyclohexanone intermediate, from which cyclohexylamine and aniline are formed in the parallel process via cyclohexylideneamine. From reaction-rate measurements on Pt/SiO2 catalysts with different Pt particle size, the amination reaction has been found to be structure-insensitive. The catalytic activity decreases with time on stream probably because of the deposit of carbonacious or polymeric materials on the catalyst surface.
ESR Studies of a New 3dz2-Type Copper(II)–Crown Ether Complex with Pentagonal Bipyramidal Geometry
Authors: Li Yong , Tajima Kunihiko , Ishizu Kazuhiko , Azuma Nagao
Published: July 2006

In the presence of the optimum amount of water, the copper(II) ion and 15-crown-5 (15C5) derivatives gave the dihydrated complex in boron trifluoride–diethyl ether (BF3–ether). Based on optical and ESR spectrometric titrations, we found that the crown ether captures the copper(II) ion in the equivalent metal/ligand molar ratio. The d–d band absorptions of the complexes were detected in the near-infrared region. The complexes revealed the characteristic ESR g-anisotropies (gz<gx, gy) which are typical of the copper(II) complexes with a 3dz2 ground-state doublet. The superhyperfine splittings due to the 17O isotope was successfully detected, and the fact of the axial ligation of the water molecule was demonstrated. The ESR parameters were determined by means of the computer simulation of the line shape, while the copper-ligand bonding parameters were estimated from the ESR parameters by means of Bleaney’s calculation.
Redox Reactions of cis-Dialkylcobalt(III) Complexes with Benzyl and Allyl Bromides, Induced by Thermal Cleavage of the Cobalt–Carbon Bond
Authors: Ishikawa Kunio , Fukuzumi Shunichi , Tanaka Toshio
Published: July 2006

The thermal cleavage of the cobalt–carbon bond of cis-dialkylcobalt(III) complexes, cis-[R2Co(bpy)2]+(R=Me, Et, and PhCH2; bpy=2,2′-bipyridine), was enhanced by the presence of benzyl and allyl bromide, inducing the C–C bond formation to yield mainly 1,2-diphenylethane and 1,5-hexadiene, respectively. In the cis-[(PhCH2)2Co(bpy)2]+-allyl bromide system, a comparable amount of the cross-coupling product (4-phenyl-1-butene) was obtained together with the homo-coupling products (1,2-diphenylethane and 1,5-hexadiene). The enhancement of the thermal cleavage of the cobalt–carbon bond of cis-[R2Co(bpy)2]+ by the reactions with benzyl and allyl bromides is caused by the high reactivity of the carbanion ligand of [RCo(bpy)2]+ produced by the homolytic cleavage of the cobalt–carbon bond of cis-[R2Co(bpy)2]+, which undergoes the exchange, coupling, and cross-coupling reactions with benzyl and allyl groups of the bromides. Based on the kinetics and the activation parameters, the cobalt–carbon bond dissociation enthalpy of cis-[(PhCH2)2Co(bpy)2]+ has been estimated to be 92 kJ mol−1.
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

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>CO32−>>gly, ala>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

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

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

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

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

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

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

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

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

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

(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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Excitation Wavelength Dependence of Phosphorescence and Hydrogen-Bonding Formation of Thioxanthone and 2,4-Diisopentylhioxanthone
Authors: Morita Hiroshi , Mori Shigeyasu , Yamaoka Tsuguo
Published: July 2006

Phosphorescence spectra of the ethanol solutions of thioxanthone(TX) and 2,4-diisopentylthioxanthone (DITX) exhibited excitation wavelength dependence at 77 K. In addition to the normal phosphorescence observed at 450 nm for TX and at 460 nm for DITX, a new red-shifted phosphorescence was resolved at 470 nm and 485 nm, respectively, when TX and DITX were excited at the absorption tail. The lifetimes and excitation spectra of the red-shifted phosphorescence were found to differ from those of the normal phosphorescence. Based on the study on UV absorption spectra and phosphorescence spectra measured with hydrated species of TX and DITX in ethanol–water solution at 77 K, the red-shifted phosphorescence is ascribed to the hydrogen-bonded species with water. In 2-methyltetrahydrofuran, phosphorescences of TX and DITX shift to the longer wavelengths and the lifetimes become longer when excited at the longer absorption tail, although the phosphorescence excitation spectra do not change appreciably.
Pressure-Induced Phase Transition and Superconductivity in Phosphorus
Authors: Shirotani Ichimin , Kawamura Haruki , Tsuji Kazuhiko , Tsuburaya Kazuhiko , Shimomura Osamu , Tachikawa Kyoji
Published: July 2006

The pressure-induced superconductivity in black phosphorus was measured along five different paths in a P–T phase diagram. The effect of the pressure on the superconducting transition temperature(Tc) depends strongly on the path in the P–T phase diagram. The results for several paths were compared with those obtained by Wittig et al. If black phosphorus was pressurized at the temperature of liquid helium, the Tc went up to 10.7 K and the onset temperature of transition was beyond 13 K at very high pressures. When red phosphorus was used as the starting material and pressurized at 4.2 K, Tc steeply increased with an increase in the pressure; it increased up to 13 K, while the onset temperature of transition reached 18 K at 30 GPa. This is the highest superconducting transition temperature among the elements. Pressure-induced phase transitions have also been studied by the X-ray techniques using synchrotron radiation at the temperature of liquid nitrogen. The pressure of the transition at 77 K was higher than that at room temperature. Two or three phases coexisted in a wide pressure (6–14 GPa) at 77 K.
Why Does the Hückel Rule Hold for a Variety of Monocyclic Conjugated Systems?
Authors: Aihara Jun-ichi , Ichikawa Hiroshi
Published: July 2006

Hückel’s 4n+2 rule is shown to be applicable to diverse monocyclic π systems by means of graph theory and frontier orbital theory. All monocyclic (4n+2)-π-electron systems are proved to have both kinetic and thermodynamic stabilities. They are predicted to be diatropic in nature.
Azoxy- and Azoferrocenes, and N-(Ferrocenylarylmethylene)anilines Formed via Aryliminodimagnesium(IDMg) Procedure. Effect of Ferrocenyl Group on IDMg Reaction and Molecular Structures of Products
Authors: Tsutsumi Toshiki , Okubo Masao , Yasuoka Noritake , Katsube Yukiteru
Published: July 2006

Some unsymmetrical azoxy- and azoferrocenes and N-(ferrocenylarylmethylene)anilines were obtained by the reactions of aryliminodimagnesium reagents (ArN(MgBr)2) with nitro- and aroylferrocenes. The types of products were same as those obtained in the similar reactions with nitrobenzenes and benzophenones. The different distribution of products arising from quite mild reactions was understood by the effect of bulky and electron-rich ferrocenyl group which retards the initial coordination and electron transfer processes, in comparison with that of phenyl group. The characteristic molecular structures of the new ferrocene compounds were studied by means of electronic absorption, 1H NMR, and X-ray crystallography. The results were summarized and discussed.
Heat Capacity of CH3D Adsorbed on Graphite at Monolayer Coverages between 0.3 and 7 K
Authors: Inaba Akira , Morrison James Alexander
Published: July 2006

Heat capacity measurements have been made on CH3D adsorbed on exfoliated graphite (Grafoil MAT) over the temperature range 0.3<T<7 K at two surface coverages near a monolayer, to evaluate predictions of the energy states of the adsorbed molecules, based on earlier studies of the properties of bulk solid CH3D and other isotopic methanes. Two Schottky-type anomalies are observed with maxima at 2 and 0.1 K; these are consistent with the predictions in a general way.
Molecular Orbital Treatment of Some Amino Acids
Authors: Abu-Eittah R , Obaid A , Basahl S , Diefallah E
Published: July 2006

INDO-molecular orbital calculations have been performed on a number of amino acids, namely, alanine, phenylalanine, some tyrosines and histidine. Computations on N-acetylhistidine are included for comparison. The results obtained for the charge densities and dipole moments were used to get a “structurefunction” correlation.
Complete Computer Analysis of NQR Data
Authors: Nogaj Boleslaw
Published: July 2006

Theories explaining temperature dependences of frequency, line width and spin-lattice relaxation times in Nuclear Quadrupole Resonance (NQR) spectroscopy have been presented in the form of mathematical expressions. Hence a complete analysis of experimental data can easily be implemented on any microcomputer. This was demonstrated by the results obtained from 35Cl NQR studies of p,p′-DDT. The computer analysis allowed to separate different mechanisms of quadrupole relaxation and determine characteristic parameters: moments of inertia of the molecule, librational frequencies and activation energies of rotating molecular groups. Besides numerical values, the printer working with the computer can produce plots of experimental points in different coordinate systems as well as the fit curves.
Molecular Rearrangements. XXVIII. Thermolysis and Photolysis of Some Hydroxamic Acid Derivatives
Authors: Badr M Z A , Fahmy A M , Mahgoub S A , Aly M M
Published: July 2006

Thermolysis and photolysis of benzohydroxamic acid and some of its derivatives have been investigated. Thermolysis of benzohydroxamic acid (BHA) either by heating in air or in a sealed tube gives NH3, H2O, CO, benzil, aniline, o- and p-aminophenols, phenoxazine, benzanilide, and benzoic acid. Whereas, thermolysis of N-(benzyloxy)benzamide (BBA) affords toluene, benzaldehyde, bibenzyl, stilbene, phenanthrene, acridine, and o- and p-aminodiphenylmethane in addition to the previous products. Analogous products were also obtained on pyrolysis of phenylacetohydroxamic acid. Photolysis of BHA and BBA in acetonitrile gives similar results to those of pyrolysis. A free-radical mechanism involving homolysis at different sites was postulated to account for the formation of such products.
Pinacol–Pinacolone Rearrangement Promoted by Polyphosphoric Acid Trimethylsilyl Ester (PPSE)
Authors: Kakimoto Masa-aki , Seri Takuya , Imai Yoshio
Published: July 2006

Pinacols afforded the corresponding pinacolones in high yields in the presence of the polyphosphoric acid trimethylsilyl ester (PPSE) at a temperature above 80 °C. Tetraphenylethylene oxide, in addition to benzopinacolone, was obtained in the reaction of benzopinacol under milder conditions. The solvent effect suggested that the rearrangement proceeded via the carbonium-ion intermediate.
Reinvestigation of the Diastereoselectivity of Kinetic Aldol Condensation of Cyclohexanone Lithium Enolate with Benzaldehyde
Authors: Hirama Masahiro , Noda Takeshi , Takeishi Shoichi , Itô Shô
Published: July 2006

Aldol condensation of cyclohexanone lithium enolate with benzaldehyde has been shown to give a considerably higher stereoselectivity at low temperature than that reported previously.
Diverse Kinetic Behaviors of the β-Structure Formation. A Study on Poly(S-carboxymethyl-l-cysteine)
Authors: Fukada Kazuhiro , Hattori Hideyuki , Maeda Hiroshi , Ikeda Shoichi
Published: July 2006

The pH jump kinetics of random coil-to-β-structure convertsion of poly(S-carboxymethyl-l-cysteine) were examined on two samples of degree of polymerization (DP) of 330 and 560. Various kinetic behaviors were observed depending on polymer chain length and concentration: single exponential with or without a lag and two exponential behavior. In unbuffered solutions, the rate enhancement of β-formation was confirmed.
Spherical Aromaticity of Buckminsterfullerene
Authors: Aihara Jun-ichi , Hosoya Haruo
Published: July 2006

Aromatic stabilization of buckminsterfullerene is not large enough to guarantee isolation in macroscopic amounts. This does not rule out the possibility that such carbon clusters are formed in sooting flames and/or in dark interstellar space.
Absorption and CD Spectral Properties of Bis(ethylenediamine)cobalt(III) Complexes with O-Bonded Sulfoxide and Seleninate
Authors: Konno Takumi , Okamoto Ken-ichi , Hidaka Jinsai
Published: July 2006

The absorption and CD spectral behavior of [Co{OS(CH3)CH2CH2NH2}(en)2]3+ and [Co{OSe(O)CH2CH2NH2}(en)2]2+ was discussed. The O-bonded seleninato isomer, Λ-(+)500CD-[Co{OSe(O)CH2CH2NH2}(en)2]2+, showed racemization at the chiral selenium atom in an aqueous solution and a shift of the equilibrium between the (R) and (S) configurations of the chiral selenium atom through the protonation on the pendant oxygen atom.
Dehydrooligopeptides. IX. Syntheses and Conversions of α-Dehydroglutamine Derivatives to N-Carboxy-α-dehydroglutamine Anhydride and Δ1-Dehydroglutaminyldipeptides
Authors: Yonezawa Yasuchika , Takefuji Nobuo , Takahashi Nobuyuki , Shin Chung-gi
Published: July 2006

Various kinds of Cbz-α-dehydroglutamine derivatives were synthesized by the reaction of Cbz-α-dehydroglutamic acids with a few primary amines, including l-α-amino acid ester, and subsequently transformed to N-carboxy-α-dehydroglutamine anhydride and several Δ1-dehydroglutaminyldipeptides.
Electrophilic and Nucleophilic Substitutions of 2-Amino- and 2-Hydroxy-1,3-diazaazulenes
Authors: Ebine Seiji , Takahashi Kazuko , Nozoe Tetsuo
Published: July 2006

2-Amino- (2) and 2-hydroxy-1, 3-diazaazulenes (3) underwent smoothly electrophilic bromination under basic conditions to give 2-amino-4,6,8-tribromo- (4) and 6-bromo-2-hydroxy-1,3-diazaazulenes (7), respectively. Bromo derivatives 4 and 7 underwent some nucleophilic substitutions, e.g., 4 reacted with ease with sodium methoxide to give 2-amino-4,6,8-trimethoxy-1,3-diazaazulene (10).
The Study of Partition Coefficients. The Prediction of Log P Value Based on Molecular Structure
Authors: Kasai Kenji , Umeyama Hideaki , Tomonaga Atsushi
Published: July 2006

An effort has been made to determine the partition coefficients from the physical quantities based on the molecular structure. The quantities are representatives of energies which constitute the solvation energy of the solute molecule. The logP value is expressed with them as

logP=−1.26+3.78φct−0.72μ1−1.28μ2

(N=244, R=0.959, S.D.=0.54, F=934).

For the practical use, the following equation is recommended:

logP=−1.36+3.89φct−1.09μ2−0.085UH+0.021UC−0.134UN−0.198UO

(N=244, R=0.976, S.D.=0.42, F=787).

Here, φct is the representative related to the charge-transfer energy and μ1, μ2, UH, UC, UN, and UO are those related to the electrostatic energy. The molecular structure of the solute molecule has been shown to be very important in the determination of the logP value. A logP value with a higher precision can be obtained by modifying the approximations used.
Conductive Salts of Tropylium Ions with Tetracyanoquinodimethan Anion Radical (TCNQ\ewdot) and Bisthiadiazolotetracyanoquinodimethan Anion Radical (BTDA–TCNQ\ewdot)
Authors: Yamashita Yoshiro , Hagiya Koji , Saito Gunzi , Mukai Toshio
Published: July 2006

Tropylium ions have been found to be good cations for forming highly conductive salts of TCNQ\ewdot. Tropylium ions with different reduction potentials were prepared. The first reduction potentials which are correlated with the substituent constants σp+ control the formation of the salts. The cations with higher reduction potentials underwent a reaction with TCNQ\ewdot to give neutral TCNQ and coupling products. The molar ratios of the initially formed salts are also dependent on the reduction potentials. The simple salts are only formed when the reduction potentials are lower than −0.43 V. This fact is rationalized by the difference in the ease of electron transfer from TCNQ\ewdot to tropylium ions which is determined by the reduction potentials. Some simple salts show significantly low electrical resistivities compared with usual TCNQ\ewdot simple salts. BTDA–TCNQ\ewdot also gave conductive salts of tropylium ions, indicating that BTDA–TCNQ is useful for forming organic semiconductors.
Dielectric Properties of the Hydrogen-Bonded Liquids. Steric Effects on Dielectric Properties in Isomeric Methylcyclohexanols
Authors: Takeshita Kimiya , Ikada Eiji , Ashida Michio
Published: July 2006

The dielectric properties of 2- and 4-methylcyclohexanols were studied in order to elucidate the molecular geometric dependences of the dielectric properties of alcohols. The Kirkwood correlaton factors g of the trans isomers are larger than those of the cis isomers. Especially the g of cis-2-methylcyclohexanol at 298 K is 0.75. The dielectric relaxation of all the methylcyclohexanols studied shows the characteristics of the Debye-like behavior frequently reported for primary alcohols. The activation energy of dielectric relaxation of 2-methylcyclohexanol is much larger than that of the other methylcyclohexanols. These facts are discussed in terms of the difference of the steric hindrance for the association through the hydrogen bond.
Proton Transfer and Aggregation Reactions in Aqueous Solutions of Isobutylamine and Isopentylamine Studied by Ultrasonic Methods
Authors: Nishikawa Sadakatsu , Yoshida Yukio , Nakano Ayumi
Published: July 2006

Ultrasonic absorption and velocity measurements have been performed in aqueous solutions of isobutylamine and isopentylamine at 25 °C. Two different relaxation phenomena are observed in these sample solutions. One of them, observed at a high frequency range, has been attributed to a proton transfer reaction of amines from the concentration dependence of the relaxation frequency and the maximum excess absorption per wavelength. The rate and thermodynamic constants have been determined for ion-pair formation and dissociation. The other, observed at a low frequency range becomes more striking as the hydrophobicity of the solute increases; it has been considered that the cause of the relaxation may be associated with a hydrophobic interaction. The formation of small aggregates has been speculated in both solutions. The rate and thermodynamic constants for the association and dissociation reactions of nonionized amine molecules have been estimated from the concentration dependences of the relaxation frequency and the maximum excess absorption per wavelength. Furthermore, the coupling effect of the two relaxation processes has been discussed briefly.