bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nucleophilic Aromatic Substitution on 1-Alkoxy-2-naphthoates with 1-Naphthyl Grignard Reagents. A Practical and Convenient Asymmetric Synthesis of 1,1′-Binaphthyl-2-carboxylates
Authors: Hattori Tetsutaro , Hotta Hiroki , Suzuki Takatsugu , Miyano Sotaro 
Published: August 2006

Abstract
1-Naphthyl Grignard reagents efficiently displace the 1-alkoxyl group of 1-alkoxy-2-naphthoic esters to provide an easy access to the corresponding 1,1′-binaphthyl-2-carboxylates in excellent yields; isopropyl ester is bulky enough to prevent the Grignard addition to the ester carbonyl function. High levels of asymmetric induction (up to 98% optical yield) have been achieved in the joining of the two naphthalene rings by using 1-(l-p-menth-3-yloxy)-2-naphthoates, while the reaction of chiral alkyl esters of 1-methoxy-2-naphthoic acid proceeded with appreciable to moderate stereoselectivity. The probable reaction mechanisms are discussed for the binaphthyl coupling and the asymmetric induction.
A Convenient Synthesis of 1,2-Dithietes and 1,2-Dithioxo Compounds Stabilized by Buttressing and Resonance Effects, Respectively, by Sulfuration of Alkynes with Elemental Sulfur
Authors: Choi Keun Soo , Akiyama Isao , Hoshino Masamatsu , Nakayama Juzo 
Published: August 2006

Abstract
Sulfuration of a series of alkynes by elemental sulfur was investigated. Alkynes carrying highly bulky substituents, 2,2,5,5-tetramethyl-3-hexyne (6a), 1,2-di-(1-adamantyl)ethyne (6b), 3,3-dimethyl-1-phenyl-1-butyne (6c), and 1-(1-adamantyl)-2-phenylethyne (6d), reacted with sulfur to give the corresponding stable 1,2-dithietes 7a—d in 46—65% yields. Less hindered alkynes reacted with sulfur to afford 1,4-dithiins and thiophenes as the final products which were derived from the initial products, 1,2-dithietes, via their tautomerization to the corresponding 1,2-dithioxo compounds, while extremely congested alkynes failed to react with sulfur even under forcing conditions. On the other hand, ynamines, a typical electron-rich alkyne, 1-diethylamino-2-phenylthioethyne (6o), 1-diethylamino-2-phenylselenoethyne (6p), and tetraethylethynediamine (6q) were sulfurated under milder conditions to afford resonance-stabilized 1,2-dithioxo compounds 19o—q as the principal products. Mechanism of the formation of 1,2-dithietes, 1,2-dithioxo compounds, and other products is discussed.
Trace Metals in Nigerian Crude Oils and Their Heavy-End Distillates
Authors: Olajire Abass A , Oderinde Rotimi A 
Published: August 2006

Abstract
Energy dispersive X-ray fluorescence spectroscopy was used to determine Fe, Hg, V, Cd, Pb, Mn, Ni, Zn, Cu, As, and Se in samples of crude petroleum and their heavy residual oils boiling above 387 °C (729 °F) from different oil producing companies in Nigeria. Vanadium, nickel, iron, and copper are the most abundant elements, and their concentrations ranged from 14 to 99 ppm; 5.0 to 11 ppm; 43 to 110 ppm and &lt; 0.05 to 54 ppm respectively. Other metals, i.e. Cadmiun and manganese were observed at the 2.4 to 8.9 ppm level while mercury, zinc, lead, arsenic, and selenium are present in very low level (0—1.4 ppm). An attempt was made to establish the distribution pattern of vanadium and nickel in the crude petroleum and their heavy residual oils.
A Computational Approach to the Structure of 4-Alkoxy-4′-cyanobiphenyl in Nematic Mesophase
Authors: Ono Isamu , Kondo Shoichi 
Published: August 2006

Abstract
Computer simulations were carried out to study the structural properties of the nematogens, nOCB (n = 5—8). The order parameters for the individual C–H bonds in the alkoxyl chain decreased stepwise along the chain in a manner similar to that determined by NMR techniques. A small difference in the ratio of molecular length to width for the compounds studied appeared according to the flexibility in the chain. The calculated densities and anisotropies in the self-diffusion coefficients were found to decrease with increasing number of carbons in the chain.
Effects of Metal Ions on Delayed Chemiluminescence Reaction of Luminol Catalyzed by Copper(II)
Authors: Kamidate Tamio , Ishikawa Atsushi , Watanabe Hiroto , Abe Shokichi 
Published: August 2006

Abstract
The delay time and chemiluminescence (CL) intensity in delayed-luminol CL catalyzed by copper(II) were remarkably affected by the presence of such metal ions as Cr(III), Mn(II), Co(II), and Ni(II). The variation of the delay time could be explained in terms of the effects of the metal ions on the oxidation rate of cysteamine by Cu(II). Meanwhile, all of the metal ions reduced the CL intensity compared with that by Cu(II) alone. This result could be ascribable to a deactivation of Cu(II) by the metal ions for the decomposition of hydrogen peroxide, thus decreasing the CL emission due to the peroxidation of luminol.
Determination of the Absolute Configuration of (−)-2,2,2-(Trifluoro-1-hydroxyethyl)ferrocene
Authors: Goto Midori , Yamazaki Yoshimitsu , Uebayasi Masami 
Published: August 2006

Abstract
The absolute configuration of the title compound produced by the microbial reduction was determined through the anomalous dispersion effect of the iron atoms. The crystals are monoclinic, space group P21, with a = 10.046(2), b = 8.844(1), c = 12.802(2) Å, β = 95.61(1)°, V = 1132(1) Å3, Z = 4, Dc = 1.666 g cm−3. There are two independent molecules in the asymmetric unit. Both of them have the same chirality of R configuration, though their molecular conformations are different.
Epoxidation of Polyolefin by Peroxy Acid Generated in situ
Authors: Kurusu Yasuhiko , Masuyama Yoshiro , Yanagi Keita , Morinaga Hiroshi , Yamamoto Shigeharu , Makanishi Mitsunori 
Published: August 2006

Abstract
The epoxidation of a new type polyolefin copolymer, poly(ethylene-co-1,9-decadiene) (PED) was carried out with performic acid produced in situ from formic acid and 35% hydrogen peroxide. The reaction was performed at room temperature or at 50 °C with conversion of vinyl group in the polymer chain and high selectivity to epoxide.
Formation of Aggregates of N-Acyl-l-amino Acids in Methanol Solutions. An Origin of CD
Authors: Mizuno Kazuko , Sirato Sohichiro , Inoue Kenji , Ogura Yasushi , Isa Kimio , Shindo Yohji 
Published: August 2006

Abstract
CD, UV, and FT-IR measurements were carried out on methanol solutions of N-dodecanoyl-l-glutamic acid and of N-dodecanoyl-l-valine over a concentration range of 5 × 10−3—1 × 10−1 M. A large positive CD band at 212 nm and a small negative one at 240 nm were observed. The positive CD decreased along with a simultaneous increase in the negative CD upon heating. Weak absorption due to a carboxylic carbonyl was found in the wavelength region where the CD bands were observed. The IR measurements reveal that carboxylic acid dimers are formed predominantly over the concentration range studied, and that an amide group does not take part in the formation of a hydrogen bond.
The two CD bands are explained in terms of the presence of two rotational conformers about the C1–C2 bond of the carboxylic group. This conclusion differs from the assignment of the positive CD band previously reported, which was ascribed to hydrogen bonding between the C*–COOH carbonyl and NH groups.
Rotational Excitation in the N2(C3Πu) and N2+(B2Σ+u) States Produced by Electron Impact of N2
Authors: Tokue Ikuo , Wang Jundong , Ito Yoshio&lt;FNR RID="N01"&gt; 
Published: August 2006

Abstract
Rotational state distributions of N2(C3Πu) and N2+(B2Σ+u) produced by electron impact on N2 have been measured by observing the 0–0 band of the N2(C3Πu—B3Πg) and N2+(B2Σ+u—2Σ+g) emissions, respectively. The average rotational quantum number for N2(C) decreases with increasing impact energy up to 30 eV (so-called rotational excitation), reaches a minimum, and increases with impact energy above 45 eV. The rotational excitation has been observed in formation of N2(C) for the first time. This trend indicates the importance of multipole interactions between the target N2 molecule and the incident electron.
Solution and Solid State High Resolution 13C NMR Studies on Tetraphenylchlorins
Authors: Nozawa Tsunenori , Nishimura Mitsushi , Hatano Masahiro , Sato Mitsuo 
Published: August 2006

Abstract
High-resolution 13C NMR spectra in solid and solution states were observed for tetraphenylchlorin (TPC), tetraphenylbacteriochlorin (TPBC), and tetraphenylisobacteriochlorin (TPIBC). Chemical-shift assignments of the 13C NMR signals for TPBC were completed by a comparison of the 1H decoupled solution 13C NMR spectra with non-decoupled and solid state ones. The absence of signal number changes by temperature in the solution 13C NMR spectra and their comparison with those of the solid state ones suggested the absence of an NH tautomerism in the chlorin ring for TPC and TPBC, indicating the predominant stability of one tautomer over the other. On the other hand, for TPIBC the presence of temperature-dependent signal number changes in the solution 13C NMR spectra were observed. The rate constants of cross polarization (CP) (TCH) and the 1H spin-lattice relaxation time in the rotating frame (T1ρH) were determined based on the dependence of the NMR magnitude on the contact time.
Cycloreversion of Aryl-Substituted Cyclobutene by Direct Photolysis and Pulse Radiolysis
Authors: Nakabayashi Kenichi , Tahara Yasuhisa , Yasuda Masahide , Shima Kensuke , Takamuku Setsuo 
Published: August 2006

Abstract
The cycloreversion of 1,5-diphenylbicyclo[3.2.0]hept-6-ene (1) to 1,4-diphenyl-1,3-cycloheptadiene (2) has been studied by direct photolysis and radiolysis. The γ-radiolysis of 1 in benzene gave 2 quantitatively up to a stationary state where the ratio of 1 to 2 is 0 : 100. However, no isomerization of 2 to 1 occurred. The triplet state of 2 (λmax = 380—385 nm; τ = 2.7—2.8 μs) was formed by pulse radiolysis of 1 in benzene. It has been found that cycloreversion proceeds by an adiabatic mechanism via the triplet state. On the other hand, the quantum yield for the formation of 2 by the irradiation of 254 nm light to 1 was determined to be 0.64 in hexane. The fluorescence spectra of 1 and 2 also indicated that diabatic cycloreversion occurred. The singlet and triplet energy values of 1, as well as those of 2, were estimated to be 102, 78, 75, and 40 kcal mol−1, respectively. The energy difference between the ground states of 1 and 2 was determined to be 20 kcal mol−1 from DSC measurements.
Micellization of Sodium Dodecyl Sulfate in Sodium Acetate–Acetic Acid Buffer. A Conductivity Study
Authors: Paul Babul Chandra , Ismail Kochi 
Published: August 2006

Abstract
Electrical conductivity of sodium dodecyl sulfate (SDS) in sodium acetate–acetic acid buffer solutions was measured as functions of concentration, temperature and pH. First and second critical micelle concentrations (cmc1 and cmc2) of these solutions were estimated. Plot of cmc1 versus pH passes through a minimum in the pH range 5.2 to 5.6. The decrease in cmc1 with increasing pH is shown to be due to the Na+ counterion and is described quantitatively by an analytical expression which also provides the value of counterion binding constant. The increasing tendency of cmc1 with increase in pH is, on the other hand, caused by the acetate co-ion. The enthalpy and standard free energy changes due to micellization of SDS were estimated. The slope of the specific conductivity versus concentration plot above cmc2 is found to decrease with increasing concentration of sodium acetate which is contrary to the trend reported in sodium chloride solution. This study has revealed the effect of the nature of co-ion on micellization.
On the Formation of Inorganic Colloid Particles
Authors: Lasic Danilo D 
Published: August 2006

Abstract
A qualitative model for the formation of inorganic colloidal particles is presented. The model is based on the symmetry of the complexes in solution and on the symmetry of distribution, i.e., position and orientation of the binding sites of the complexes. These factors determine the final particle shape when particles grow by crystallization, while in the case of additional secondary aggregation, it is controlled also by the factors which determine crystal habit and stability of colloidal particles. In addition, kinetic factors have to be considered also because the systems are normally driven through various phases far from themodynamic equilibrium.
Molecular Mechanics Studies on the Ligand Conformation of Chiral Ruthenium Tris(2,2′-bipyridine)-Type Complexes
Authors: Ishida Hitoshi , Hamada Taisuke , Fujishita Yu-ichi , Saito Yuri , Ohkubo Katsutoshi 
Published: August 2006

Abstract
Molecular mechanics (MM) calculations were performed for two chiral ligands, 4,4′-bis[R(or S)-phenylethylamino carbonyl]-2,2′-bipyridine (R(or S)-PhEtbpy) and 4,4′-bis(menthoxycarbonyl)-2,2′-bipyridine (Menbpy) by the MM2PRIME program with several new parameters. These ruthenium complexes have been already found to be efficient catalysts for photochemical and enantioselective electron transfer reactions. The bonded terms in the new parameters were determined by Hopfinger's method with molecular orbital (MO) calculations. The MO calculations were mainly performed with AM1 program, however some torsional parameters were also determined by ab initio MO methods to compare with the results derived by semi-empirical methods. The electrostatic parameters were determined with the AM1 program by using the electrostatic potential (ESP) method. To find the most stable conformation, the contour maps of the strain energy of the chiral ligands were drawn as a function of rotation of the chiral groups, and the favorable conformation obtained was supported by 1H NMR measurement. The structures of these ruthenium complexes were also discussed on the CD spectra of the complexes and the enantioselectivity of the reaction.
Dependence of Ni Corrosion with a (Li0.62K0.38)2CO3 Coating on the Temperature and Atmosphere
Authors: Ota Ken-ichiro , Kim Baek-un , Yoshitake Hideaki , Kamiya Nobuyuki 
Published: August 2006

Abstract
The corrosion of Ni coated with alkali carbonates was measured in a CO2/O2 atmosphere at 873—1173 K. The corrosion of Ni coated with carbonates generally obeyed a parabolic rate law under a 67% CO2–33% O2 atmosphere. The parabolic rate constant decreased with an increase in the temperature with a (Li0.62K0.38)2CO3 coating under a 67% CO2–33% O2 atmosphere. This was explained by the solubility of NiO that was formed on Ni metal during corrosion. Hot corrosion was observed several times with (Li0.62K0.38)2CO3 under low CO2 pressure at 1073 K. This hot corrosion could be explained by the dissolution/reprecipitation mechanism of the NiO scale, due to the solubility gradient in the carbonate film.
The Effects of Vapor Sorption in Polymers Observed by Positron Annihilation
Authors: Ito Yasuo , Sanchez Victor , Lopez Rafael , Fucugauchi Luz A , Tanaka Kazuhiro , Okamoto Kenichi 
Published: August 2006

Abstract
Positron lifetime measurements were performed for two different kinds of polymers (low density polyethylene and a polyimide 6FDA-TMPD) during sorption of various vapors (hexane, cyclohexane, benzene, acrylic acid, methyl acrylate, water, and oxygen). The vapor sorption affected the long-lived component (ortho-positronium component) in a systematic way regardless of the kind of the vapor molecules, i.e. for the polyethylene both the lifetime and the intensity of the long-lived component were enhanced, while for the polyimide they were decreased significantly. These different effects are interpreted in terms of different states of sorbed molecules in rubbery (the polyethylene) and in glassy (the polyimide) polymers.
Photovoltaic Properties of Porphyrin Thin Films Mixed with o-Chloranil
Authors: Takahashi Kohshin , Horino Kenji , Komura Teruhisa , Murata Kazuhiko 
Published: August 2006

Abstract
By mixing Zntpp solid with o-chloranil, the rectification and photovoltaic properties of Al/porphyrin/Au sandwich-type cell are improved (Zntpp: 5, 10, 15, 20-tetraphenylporphyrinatozinc). The improvement may be mainly attributable to an increase in the hole concentration as the majority carrier because of the electron transfer from Zntpp to o-chloranil in the ground state. In addition, by mixing H2tpp solid with o-chloranil, the short circuit photocurrent of the sandwich-type cell increases although the rectification property is hardly improved (H2tpp: 5, 10, 15, 20-tetraphenylporphyrin). The fluorescence intensity, the short circuit photocurrent and its temperature-dependence for various porphyrin solids mixed with o-chloranil are measured in order to clarify the photogeneration mechanism of charge carriers. The results suggest strongly that an exciplex formed between H2tpp and o-chloranil molecules contributes to the photogeneration of charge carriers.
Fluorescence Spectra of Pyrene and Humidity Effects on Them during the Sol-to-Gel-to-Xerogel Transitions of Mixed Silicon–Aluminum Alkoxide Systems
Authors: Fujii Tsuneo , Murayama Kei , Negishi Nobuaki , Anpo Masakazu , Winder Edmund J , Neu Donald R , Ellis Arthur B 
Published: August 2006

Abstract
The fluorescence spectra of pyrene of four sol systems comprising silicon and aluminum alkoxides (Si : Al = 99.4 : 0.6 ; 93.6 : 6.4; 85.9 : 14.1; and 50 : 50) have been observed during sol-to-gel-to-xerogel transitions under at relatively low concentration, on the order of 10−4 mol dm−3, uncatalyzed, and constant temperature (300 K) conditions. The influence of relative humidity on the relative intensities of pyrene monomer and excimer-like fluorescence in the four xerogel states has also been observed. In three of the four systems studied (all but Si : Al = 99.4 : 0.6), fluorescence spectra revealed that excimer concentration increased with time and reached a maximum near 55 days after which it decreased. From our data, it is apparent that the ratio of the intensity of the excimer-like fluorescence to that of the monomer fluorescence increases with relative humidity.
Charge Recombination Process in X-Ray Irradiated Pyrene-Doped Polystyrene as Studied by Optically Detected Electron Spin Resonance and Magnetic Field Dependence of the Recombination Fluorescence
Authors: Okazaki Masaharu , Tai Yutaka , Toriyama Kazumi 
Published: August 2006

Abstract
The ODESR spectrum and magnetic field dependence on recombination fluorescence were observed for X-ray irradiated pyrene-doped polystyrene at temperatures of 242—348 K. The ODESR intensity as a function of the pyrene concentration, 0.1—8.9 wt%, showed an unusual minimum at about 1.0%. Two phases were separated in the magnetic field dependence of the fluorescence: one was sharp and saturates at fields of over 50 mT, while the other was broad with a dip at around 60—150 mT. The cause of this dip was naturally attributed to the ST−1 level crossing. The sharp magnetic field effect also showed a minimum at around a concentration of 1.0 wt%. These novel findings have been interpreted using a recombination model modified from the previous one for pyrene-doped ethylene–propylene rubber and polyethylene. The essential points of the present model are: (1) although electron hopping within the polystyrene molecule is rapid, electron transfer at the last step of recombination between the polystyrene anion and the pyrene cation proceeds at a moderate rate; (2) the hole-transfer rate in the polymer chain is moderate; (3) electron hopping between the doped pyrene molecules is very much dependent on the concentration; (4) hole hopping between the pyrenes is inhibited.
The Role of Zinc Cations in the Conversion of Isobutane into Aromatics over Mechanical Mixtures of ZnO and H-ZSM-5
Authors: Osako Kazuaki , Nakashiro Katusmi , Ono Yoshio 
Published: August 2006

Abstract
Mechanical mixtures of ZnO and H-ZSM-5 show high activities and selectivities for the aromatization of isobutane. The temperature-programmed desorption spectra of ammonia and the infrared spectra of adsorbed pyridene revealed that a solid–solid ion-exchange occurs between ZnO and H-ZSM-5. The presence of Zn cations in the zeolite channels not only enhances the dehydrogenation, but also the C–C bond cleavage of isobutane. A mechanism for the activation of isobutane is proposed.
The Kinetics and Mechanism of the Reaction of Uranium(VI) with 8-Quinolinol and 8-Hydroxy-5-quinolinesulfonic Acid
Authors: Das Asim K 
Published: August 2006

Abstract
The kinetics of the reaction of uranium(VI) with 8-quinolinol and 8-hydroxy-5-quinolinesulfonate under the conditions of 1 : 1 chelate formation in the pH range 3.6—4.6 at different temperatures (20—30 °C) and ionic strength I = 0.1 mol dm−3 (KNO3) have been studied. A dual path mechanism involving both UO2(aq)2+ and UO2(OH)(aq)+ and the partially deprotonated ligand (LH,LH−) is consistent under the experimental conditions. The different rate constants under the condition of equilibrium have been determined. The results conform to kobs/B = k1[H+] + k2Kh;
where

K h = hydrolysis constant of UO2(aq)2+; Ka(1) = first deprotonation constant of the ligand, LH2 (charges are omitted); k1 and k2 are the second order forward rate constants of UO2(aq)2+ and UO2(OH)(aq)+ respectively and Q is the equilibrium constant of the reaction, UO22+ + LH UO2L+ + H+, where LH represents the partially deprotonated form of the ligand, 8-quinolinol and a similar reaction occurs for deprotonated 8-hydroxy-5-quinolinesulfonate (LH−). Thermodynamic parameters for each of the steps have been determined. The results have been compared with those of recent findings in the interaction of cerium(IV) and iron(III) with these ligands. UO2(aq)2+ has been argued to react through a dissociative interchange (Id) mechanism and its characteristic water exchange rate has been found as a rough estimate. Similarly for UO2(OH)(aq)+, a dissociative mechanism has been speculated.
Utilization of Adduct Formation and Masking Effect for Separation of Some Metal 4-(2-Thienyl)-4-thioxo-1,1,1-trifluoro-2-butanonates and 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedionates by Reversed Phase HPLC
Authors: Suzuki Tomohiro , Tsunoda Kin-ichi , Kawamoto Hiroshi , Akaiwa Hideo 
Published: August 2006

Abstract
The separation behavior of CoIII-, NiII-, CuII-, and ZnII-STTAs [4-(2-thienyl)-4-thioxo-1,1,1-trifluoro-2-butanone] and CoII-, NiII-, and CuII-TTAs [4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] in reversed phase high performance liquid chromatography was investigated when various additives were added to the mobile phase. The adduct formation or the masking effect was observed upon addition of additives. When trioctylphosphine oxide was added to the mobile phase, mutual separation of those metal chelates was especially remarkable due to the adduct formation. Moreover, the decomposition of some metal chelates in the HPLC column was also prevented by the adduct formation. On the other hand, 2,2′-bipyridyl and 1,10-phenanthroline showed the masking effect. Such effects of additives were consistent with their synergistic extraction constants in chelate extraction.