bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Study of the Thermodynamics of Micellization of Hexadecylpyridinium Bromide
Authors: Shamsipur Mojtaba , Alizadeh Naader , Gharibi Hossein 
Published: June 2006

Abstract
A membrane electrode selective for hexadecylpyridinum bromide was used to study the micellization of the surfactant at various temperatures (25—50 °C). The thermodynamic parameters ΔH°m and ΔS°m were calculated from the temperature dependence of the equilibrium constants for micellization of the surfactant. It was clearly shown that the entropy of micellization obtained by the usual approximate method from ΔG°m = (2 − α)RTln Xcmc is much more positive than the corresponding exact value calculated from direct activity measurements.
Emulsification of Calix[4]arenes Bearing Four Chains and Transportation of Cesium Ion through Liquid Surfactant-Membrane
Authors: Koide Yoshifumi , Sato Hirotaka , Shosenji Hideto , Yamada Kimiho 
Published: June 2006

Abstract
Resorcinol-type calix[4]arenes bearing four alkyl side chains ([4]Ar-Rn) have been applied as a liquid surfactant-membrane in the concentration process of Cs+. [4]Ar-Rn formed a highly stable water-in-oil (w/o) emulsion for a mixture of toluene and HCl solution, and the w/o emulsion became a w/o/w emulsion by stirring it in a Cs+ solution. The Cs+ in the outer aqueous solution was transported through the liquid surfactant-membrane of w/o/w emulsion into the inner HCl solution. [4]Ar-R6 was the most effective emulsifier capable carrying Cs+ in the [4]Ar-Rn bearing alkyl chains of various lengths. The final amount of the transported Cs+ was 9 times as much as the molar of [4]Ar-R6 in 100 min at the initially 10 times molar Cs+ in the outer solution (turnover number: 9). Moreover, the Cs+ was transported selectively from a mixture of alkali metal ions (Cs+, Na+, and K+) by using 2 × 10−4 mol of [4]Ar-R6.
Electronic and Magnetic Properties of Activated Carbon Fibers
Authors: Nakayama Atsuko , Suzuki Kazuya , Enoki Toshiaki , Koga Kei-ichi , Endo Morinobu , Shindo Norifumi 
Published: June 2006

Abstract
Activated carbon fibers (ACF) consist of microporous carbon with a huge specific surface area (SSA) ranging from 700 m2 g−1 to 3000 m2 g−1, and a having random structures consisting of an assembly of micrographites with a dimension of ca. 20 × 20 Å2. The electrical conductivity and magnetic susceptibility were investigated for ACFs with SSA = 1000 and 2000 m2 g−1 in order to clarify the relation between the electronic properties and the structure of ACF having a random network of micrographites. The electrical conductivity is explained by the two-dimensional variable-range hopping conduction at lower temperatures and thermally activated conduction at higher temperatures. The introduction of N2 or O2 gas to a sample induces a change in the conductivity, which is considered to be caused by a structural change and a charge transfer between dangling bonds and O2 gas. The observed value of the orbital diamagnetic susceptibility is considerably small compared with that of a condensed polycyclic aromatic hydrocarbon having the same dimensions as that of the micrographite in ACF. This implies that the micrographitic domains have a deformed planar structure with the presence of defects.
Oxidation of a Dipeptide by Electrolytically Generated Manganese(III) in Aqueous Sulfuric Acid Medium: A Kinetic and Mechanistic Study
Authors: Bhat D Krishna , Sherigara B Sheena , Gowda B Thimme 
Published: June 2006

Abstract
The kinetics of oxidation of the simplest dipeptide, glycylglycine (GG) by electrolytically generated manganeseIII-sulfate in aqueous sulfuric acid has been studied. The rate shows first order dependence on [MnIII] and a fractional order each on [GG] and [H+]. The reduced product, MnII has no significant effect on the rate. An increase in ionic strength or decrease in dielectric constant of the medium increases the rate, while addition of complexing agents such as Cl−, F−, and P2O74− decreases the rate. A Michaelis–Menten type mechanism has been suggested to explain the results. The coefficient of the rate-determining step has been evaluated as a function of temperature, by measuring the rates at different temperatures. The corresponding activation parameters have also been computed. Evidence for transient existence of a free radical reaction intermediate has been given. The kinetics of oxidation of GG have also been compared with those of the monomer amino acid, glycine.
Stable β-Sheet Formation and Enhanced Hydrolytic Catalysis of a Sequential Alternating Amphiphilic Polypeptide Containing Catalytic Triads in a Serine Protease
Authors: Fukushima Yasumasa 
Published: June 2006

Abstract
The alternating amphiphilic copolypeptide poly(Asp–Leu–His–Leu–Ser–Leu) was prepared by the synthesis and polymerization of the respective hexapeptide in order to obtain a stable β-sheet polypeptide with hydrolytic catalytic activity, like that of a serine protease. The conformation and conformational transitions in aqueous solution and in water–organic solvent mixtures were determined by circular dichroism measurements. The polypeptide reveals a very strong tendency to adopt a β-sheet structure, which is accomplished at below pH 10.0, and even by adding sodium chloride or various alcohols. However, a partial α-helical conformation is observed in an aqueous solution at pH 12.0; also, an α-helix to β-sheet conformational transition occurs upon adding 1 M NaCl. The polypeptide is a more effective catalyst than the peptide hexamer, the amino acids mixture, or imidazole for the hydrolysis of p-nitrophenyl derivatives, and catalyzed the hydrolytic reaction of the substrates more effectively with increasing their hydrophobicity. It is likely that the enhanced hydrolytic catalyst of the polypeptide may be responsible for increasing the nucleophilicity by the electrostatic interactions or condensation effect of the substrates by hydrophobic interactions. The polypeptide would make good models for constructing novel proteins with catalytic properties involving β-sheet structures.
Gas Phase Basicities of Phenylacetylenes. Intrinsic Resonance Demand of the 1-Phenylvinyl Cation
Authors: Mishima Masaaki , Ariga Toshifumi , Matsumoto Takatsugu , Kobayashi Shinjiro , Taniguchi Hiroshi , Fujio Mizue , Tsuno Yuho , Rappoport Zvi 
Published: June 2006

Abstract
Gas-phase basicities (GB) of a series of substituted phenylacetylenes were determined by measuring the standard free energy changes of proton transfer equilibria using a pulsed ion cyclotron resonance mass spectrometer. The LArSR analysis of the substituent effect on the GB values gave an r+ value of 1.18 and a ρ value of −14.0. The r+ value is significantly larger than that obtained for the GB of α-methylstyrenes but is smaller than that for chloride ion affinities of benzyl cations, while the ρ value is similar in the three systems. This means that the 1-phenylvinyl cation has an intermediate resonance demand between those of the α-cumyl cation and the benzyl cation. Further, the r+ value of 1.18 for 1-phenylvinyl cation obeys the same “resonance demand vs. carbocation stability" relationship observed for a series of ordinary sp2-hybridized benzylic carbocations. This reveals that the π-delocalization mechanism in the vinyl cation system has no unique feature but it is a part of a continuous spectrum of resonance demands of varying benzylic carbocations characterized by r+ = 1.18. A comparison of the present GB values with the substituent effect for the acid-catalyzed hydration of phenylacetylenes in solution has shown that the r+ value is perceptibly smaller in the latter case. This suggests that the π-delocalization in the transition state differs considerably from that of the stable phenylvinyl cation intermediate. This is in contrast to the situation in the SN1 solvolysis where the r+ value is identical to the value characteristic for the formation of the fully developed carbocation.
Complex Metal Halide Oxides (1): Bismuth Chloride Oxides Having Various Structures as Catalysts for Oxidative Coupling of Methane
Authors: Ueda Wataru , Isozaki Toshio , Sakyu Fuyuhiko , Nishiyama Satoshi , Morikawa Yutaka 
Published: June 2006

Abstract
Bismuth chloride oxides having four distinct structural types and lanthanum-substituted bismuth chloride oxides were tested as catalysts for the oxidative coupling reaction of methane. Their catalytic properties were compared in relation with their structure. BiClO, which has a layer structure with a double chlorine sheet, so-called X2 type structure, was most active for the methane conversion but less selective for the formation of C2 hydrocarbons. The catalyst structure was quite unstable, so that the activity decreased markedly until reaching a constant level, while the selectivity increased. During these changes of the catalytic performance BiClO changed by liberating chlorine to Bi24Cl10O31, the so-called Arppe’s phase, and then finally to a highly stable and selective Bi3ClO4 phase which was constructed with a double metal oxygen sheet and a single chlorine sheet. When more chlorine was removed from Bi3ClO4, Bi12Cl2O17, which has quintuple oxide sheets and a single chlorine sheet, was formed as an intermediate phase to be less selective for C2 hydrocarbons and ultimately Bi2O3 was formed with no chlorine, to be nonselective. The substitution of Bi in Bi3ClO4 for La caused a decrease of the C2 selectivity, whereas the Bi3−xLaxClO4 catalysts treated with NaCl brought about a maximum yield of C2 hydrocarbons.
Characteristics of Iron Phosphate and Its Catalytic Activity for Oxidative Dehydrogenation of Isobutyric Acid
Authors: Muneyama Etsuhiro , Kunishige Atsuhiro , Ohdan Kyoji , Ai Mamoru 
Published: June 2006

Abstract
In the absence of oxygen, P/Fe = 1.2 catalyst samples are reduced by hydrogen or isobutyric acid to form Fe2P2O7 via Fe3(P2O7)2, while the P/Fe = 1.0 samples are reduced directly to Fe2P2O7; without passing through Fe3(P2O7)2. Fe2P2O7 is oxidized by air to an unknown compound (Y-phase), but not to Fe3(P2O7)2 nor FePO4. The Y-phase is reduced to Fe2P2O7. During the use in the oxidative dehydrogenation of isobutyric acid, freshly calcined catalysts are reduced to Fe3(P2O7)2, while the Fe2P2O7 catalysts are oxidized to Y-phase, though the rates are very slow. The catalytic activity and selectivity are scarcely affected by variation in the structure of the iron phosphate catalyst and in the oxidation states of iron ions. The P/Fe and Fe2+/(Fe2++Fe3+) ratios on the surface, which were measured from cooled catalyst samples, are almost the same as those in the bulk.
The Excimer Fluorescence of 2-Methylnaphthalene in β- and γ-Cyclodextrin Aqueous Solutions
Authors: Hamai Sanyo 
Published: June 2006

Abstract
2-Methylnaphthalene (MN) exhibits MN excimer fluorescence in both β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) neutral aqueous solutions. β-CD forms a 1 : 1 inclusion complex with MN, which self-associates to form a 2 : 2 inclusion complex emitting the MN excimer fluorescence. In 0.4 mol dm−3 NaOH solutions, no excimer fluorescence has been observed, indicating that the 2 : 2 inclusion complex dissociates to two 1 : 1 inclusion complexes because of an electrostatic repulsion between the negatively charged hydroxy groups of the two β-CD molecules contained in the 2 : 2 inclusion complex. For the γ-CD–MN system as well as the β-CD–MN system, the excimer fluorescence can be explained in terms of the formation of a 2 : 2 inclusion complex through a self-association of 1 : 1 inclusion complexes.
The Thermal Behavior of 1,3 : 2,4-Di-O-benzylidene-d-sorbitol/Ethylene Glycol Gel
Authors: Yamasaki Seiji , Tsutsumi Hisao 
Published: June 2006

Abstract
The so-called 1,3 : 2,4-di-O-benzylidene-d-sorbitol (D-DBS) can cause the gelation of alcoholic solvents. The thermal behavior of a 1 wt% d-DBS/ethylene glycol gel was studied using thermal, optical, mechanical, and spectroscopic measurements. Changes in the optical and mechanical properties were observed at around 45 and 80 °C. Upon heating, the diameter of the spherulitic texture in the gel decreased above around 45 °C and disappeared at around 80 °C. In a thermal analysis, an endothermic peak was observed at around 80 °C, which agreed with the gel state-isotropic solution phase-transition point. The aggregated structure of d-DBS in ethylene glycol was studied, using UV absorption and circular dichroism (CD) measurements. The relative orientation of the benzene rings changed above 45 °C, due to the hypochromism of the UV absorptions. The gel showed a temperature dependence of the CD spectra. With increasing temperature, the value of the molar ellipticities increased at 27—82 °C, and drastically decreased at 82—93 °C, indicating that the aggregated structure underwent a change at between 45—80 °C and disappeared above 80 °C. The macroscopic level, as well as the optical and mechanical properties were related to the change in the aggregated structure formed by d-DBS.
GPC Analysis of Polymer Network Formation: 1. Bifunctional Siloxane Monomer/Crosslinker System
Authors: Kohjiya Shinzo , Takada Yasuhiro , Urayama Kenji , Tezuka Yasuyuki , Kidera Akinori 
Published: June 2006

Abstract
The size distribution of polymer clusters in the pre-gel state was investigated as a function of the conversion by gel permeation chromatography (GPC) in order to elucidate the process of polysiloxane network formation. Polysiloxane networks were synthesized by hydrosilylation between a bifunctional monomer and a tri- or tetrafunctional crosslinker. Experimental chromatograms for the pre-gel system were compared with a theoretical one based on the distribution for the mean-square radius of gyration (&lt;S2&gt;) of polymer clusters predicted by the Flory–Stockmayer theory and the Gaussian chain statistics. Experimental chromatograms at high conversion showed a longer tailed distribution in the large &lt;S2&gt; region compared with a theoretical one. A comparison of experimental chromatograms with theoretical ones suggests the structure of a precursor network in which branched clusters are linearly linked.
Theoretical Studies of the Chemical Processes of Producing Methylamine and Methanol in the Interstellar Space
Authors: Sonoda Yoko , Iwata Suehiro 
Published: June 2006

Abstract
A hypothesis for the mechanism forming CH3NH2 and CH3OH in interstellar space is examined with the ab initio MO calculations. In the hypothesis, both of CH3NH2 and CH3OH are assumed to be formed via two steps, radiative association reaction and dissociative recombination reaction. The calculations support the possibility of the two-step mechanism for CH3OH, but the first step radiative association reaction for CH3NH2 is proved to be unfavorable. Based on the calculational results, an alternative reaction mechanism is proposed.
Synthesis, Spectral, Thermal, and Biological Studies of Adducts of Organotin(IV) Halides with Schiff Bases Derived from 2-Amino-5-(o-methoxyphenyl)-1,3,4-thiadiazole
Authors: Nath Mala , Goyal Savita , Eng George , Whalen D 
Published: June 2006

Abstract
Some new organotin(IV) complexes of the general formula, RnSnCl4−n·L [where n = 3, R = CH3 or C6H5; n = 2, R = C6H5; L = Schiff bases derived from the condensation of 2-amino-5-(o-methoxyphenyl)-1,3,4-thiadiazole with salicylaldehyde (L-1), 2-hydroxy-1-naphthaldehyde (L-2), 2′-hydroxyacetophenone (L-3), benzyl methyl ketone (L-4), acetylacetone (L-5), and 2-furancarbaldehyde (L-6)] have been synthesized and characterized by elemental analyses, molar conductances, electronic, infrared, far-infrared, 1H and 119Sn NMR and Mössbauer spectral studies. Thermal studies of three complexes, viz., Ph3SnCl(L-2), Me3SnCl(L-4), and Ph3SnCl(L-5) have been carried out in the temperature range 25—1000 °C using TG, DTG, and DTA techniques. All these complexes decompose gradually with the formation of SnO2 as an end product. In vitro antimicrobial activity of the ligands and their complexes has also been determined against Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus Penicillin resistance (2500 units), Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii, Trichophyton mentagrophytes, and Aspergillus fumigatus.
Formation of Peroxodiphosphate by the Copper(II)-Catalyzed Oxidation Reaction of the Phosphinate Ion by the Molecular Oxygen. Kinetics and Mechanisms in Aqueous Solutions
Authors: Kimura Masaru , Seki Kyouko , Horie Hitomi , Tsukahara Keiichi 
Published: June 2006

Abstract
It was found that peroxodiphosphate ions (denoted by PDP and meaning all forms of P2O84−, HP2O83−, H2P2O82−, etc.) were formed by the oxidation of the phosphinate ion (PH2O2−) by molecular oxygen (O2) using trace amounts of the copper(II) ion as a catalyst in aqueous solutions. The formation rate was dependent on the acidity being maximum at around pH 3.5, and was inhibited by the presence of radical scavengers or a complex-forming substance of ethylenediaminetetraacetic acid (EDTA). The formation of PDP was not observed when ions such as IrIV and CeIV were used in place of the copper(II) ion. Thus, this reaction is specific only for the copper(II) ion, which can be easily reduced to Cu+ by the phosphinate ion, where the reduced species are capable of reacting with molecular oxygen to efficiently produce the superoxide of O2−• or HO2•. After some PDP had been formed in the presence of air or oxygen, if the reacting solution was changed to be anaerobic by bubbling nitrogen through the solution, the PDP began to decompose according to the first-order rate law with respect to the concentrations of PDP. The kinetics and mechanisms for not only the formation, but also the decomposition of PDP, are presented.
Template-Dependent Selectivity in Metal Adsorption on Phosphoric Diester-Carrying Resins Prepared by Surface Template Polymerization Technique
Authors: Murata Masaharu , Hijiya Shinji , Maeda Mizuo , Takagi Makoto 
Published: June 2006

Abstract
The surface templated resins for three different metal ions such as Cu2+, Zn2+ or Cd2+ as the template guest were prepared by emulsion polymerization using oleyl phenyl hydrogenphosphate as a host surfactant, sodium dodecyl sulfate (SDS) as a co-surfactant and divinylbenzene as a resin matrix-forming monomer. The Cu2+-imprinted resin adsorbed Cu2+ much more effectively than did the nonimprinted, the Zn2+- and Cd2+-imprinted ones. On the other hand, the Cd2+-imprinted resin showed a more highly effective binding to Cd2+ than those of the Cu2+-imprinted, Zn2+-imprinted, and nonimprinted resins. In fact, the Cu2+-imprinted resin did not adsorb any significant amount of Cd2+. The selective feature of the surface templated resins to the target ion was thus successfully demonstrated. The template-dependent selectivity should be ascribed to a favorable placement of the surface-anchored metallophilic groups for multidentate coordination to the specific metal ion.
Crystal Structure and Chemical Properties of Tris(2,6-dimethoxyphenyl)phosphine Selenide
Authors: Wada Masanori , Hayase Shuichi , Fujiwara Masanobu , Kawaguchi Tetsuji , Iwasaki Toshio , Uo Akira , Erabi Tatsuo 
Published: June 2006

Abstract
The X-ray crystal structure of the title compound, Φ3PSe [Φ = 2,6-(MeO)2C6H3], showed that the P=Se bond distance [2.136(2) Å] was the longest among those of the reported triarylphosphine selenides, that the P–C bond distances [av. 1.839 Å] were longer than those of triphenylphosphine selenide, and that all the P···O interatomic distances [2.794—3.189 Å] were shorter than the sum of the van der Waals radii, implying a direct electron-donative interaction from the methoxy oxygen atom to the phosphorus atom. Some chemical evidence also showed that the P=Se bond was weaker than that of triphenylphosphine selenide. Alkyl halides, RX, reacted with Φ3PSe to give a mixture of alkylselenophosphonium salts, [Φ3P–SeR]X, and alkylphosphonium salts, [Φ3P–R]X, while they reacted with PhΦ2PSe to give [PhΦ2P-SeR]X almost selectively. Measurements of the reaction rates of Ph3−nΦnPY (n = 0—3; Y = none, O, S, Se) with butyl bromide in acetonitrile showed that the rate decreased in the order of Y = none &gt; Se &gt; S &gt; O and n = 3 &gt; 2 &gt; 1 &gt; 0. Benzylselenophosphonium salts, [Φ3P–SeCH2C6H4Z-4]Cl (Z = H, Me, Cl) and [PhΦ2P–SeCH2Ph]Cl, reacted easily with aqueous sodium hydroxide or with aqueous tin(II) chloride to give the diselenides, (4-ZC6H4CH2Se)2, and most of ArΦ2P [Ar = Φ or Ph] was recovered after these reactions. These properties of [ArΦ2P–SeR]X, as well as of ArΦ2PSe, were discussed in terms of the electronic effect and/or steric effect of methoxy groups at 2,6-positions.
Isomerization and Racemization of the Tris(4,4′-dimethoxy- or 4,4′-diethoxy-2,2′-bipyridine 1,1′-dioxide)chromium(III) Complexes
Authors: Kanno Hideaki , Yamamoto Junko , Utsuno Shunji , Fujita Junnosuke 
Published: June 2006

Abstract
Two new chromium(III) complexes, [Cr(4,4′-X2bpdo)3]3+ (X = MeO or EtO; bpdo = 2,2′–bipyridine 1,1′-dioxide), were prepared. These complexes form two diastereomers, lel3(Δ(λλλ), Λ(δδδ)) and lel2ob(Δ(λλδ), Λ(δδλ)), which were separated and resolved by an SP-Sephadex column chromatographic method using achiral eluting agents, such as Na2SO4 or NaCl. The isomers isomerized to each other (lel3 lel2ob) fairly rapidly in water along with changes in the absorption spectra, and then racemized very slowly (Δ Λ). These reactions, including conformational (δ λ) and configurational (Δ Λ) changes, are independent of H+ and free ligand concentrations, and are supposed to proceed by an intramolecular mechanism. For a series of [Cr(4,4′-X2bpdo)3]3+ (X = H, Me, MeO, EtO), both the rates of isomerization and racemization are remarkably reduced along with an increase in the electron-releasing ability of the 4,4′-X2 substituents on bpdo.
Direct Measurement of the Intermolecular Potentials of CH4–Xe, CH4–Kr, CH4–Ar, and CH4–Ne from the Extended Principle of Corresponding States
Authors: Boushehri Ali , Hashemi Fariba S 
Published: June 2006

Abstract
An inversion procedure is used to obtain from the extended principle of corresponding states the interaction potentials over a range of reduced temperature extending from 1 to the onset of ionization. These directly measured potentials for CH4–Xe, CH4–Kr, CH4–Ar, and CH4–Ne agree excellently with the potentials independently known from the crossed molecular-beam technique.
Cycloaddition and Oxidation Reactions of a Stable Thioaldehyde, (2,4,6-Tri-t-butyl)thiobenzaldehyde
Authors: Watanabe Soichiro , Yamamoto Toshio , Kawashima Takayuki , Inamoto Naoki , Okazaki Renji 
Published: June 2006

Abstract
The title thioaldehyde 1 undergoes [4 + 2] cycloaddition with 2,3-dimethyl-1,3-butadiene at 160 °C and [3 + 2] cycloadditions with diphenylnitrilimine and mesitonitrile oxide at room temperature. The intermediary cycloadduct with mesitonitrile oxide undergoes cycloreversion to give 2,4,6-tri-t-butylbenzaldehyde and mesityl isothiocyanate as the final products. Oxidation of 1 with m-chloroperbenzoic acid (mCPBA) and dimethyldioxirane (9) gives a mixture of (E)- and (Z)-isomers of the corresponding S-oxides (sulfines), the former and the latter being kinetically and thermodynamically controlled products, respectively. Although both (E)- and (Z)-sulfines are not further oxidized by mCPBA, the (Z)-sulfine is oxidized with 9 to give 7-oxa-8-thia-2,4,6-tri-t-butylbicyclo[4.3.0]nona-2,4,9-triene 8,8-dioxide and 6,8-di-t-butyl-3,4-dihydro-4,4-dimethyl-1H-2-benzothiopyran 2,2-dioxide, both of which are intramolecular cyclization products of an intermediary thioaldehyde dioxide (sulfene).