bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Organic Solvents on the Thermal Denaturation of Lysozyme as Measured by Differential Scanning Calorimetry
Authors: Fujita Yukihisa , Noda Yukinao 
Published: July 2006

Abstract
The thermal denaturation of lysozyme in aqueous solutions of N,N-dimethylformamide(DMF), N,N-dimethylacetamide(DMA), acetone, and dioxane at pH 3 was investigated by differential scanning calorimetry(DSC). The denaturation temperature, Td, decreased linearly with an increase in the concentration of organic solvent. The lowering in Td at identical concentrations of organic solvent increased in the order: acetone&lt;DMF&lt;DMA&lt;dioxane. The calorimetric enthalpy of denaturation, ΔHd, showed a complex dependence on the solvent composition. For three organic solvents (not dioxane), the ΔHd first increased slightly with increasing the concentration of organic solvent and then started decreasing at different concentrations of each organic solvent. This behavior is analogous to those observed earlier with monohydric alcohols and with sulfoxides. For dioxane, on the other hand, the ΔHd decreased gradually with increasing the concentration of dioxane. The effect of these organic solvents on the thermal stability of lysozyme may correlate with their effect on the structure of water, which determines the strength of the hydrophobic interaction of the protein.
The Ullmann Condensation Reaction of Haloanthraquinone Derivatives with Amines in Aprotic Solvents. V. The Formation of Active Catalyst by the Partial Oxidation of Copper(I) with Molecular Oxygen
Authors: Arai Sadao , Hashimoto Yoshio , Takayama Nobuo , Yamagishi Takamichi , Hida Mitsuhiko 
Published: July 2006

Abstract
Although copper(I) is a more effective catalyst than copper(II) in the Ullmann condensation reaction of haloanthraquinones with ethylenediamine in aprotic solvents under a nitrogen atmosphere, the oxidation products of copper(I) by molecular oxygen enhanced the reaction rate compared to copper(I) catalyst. From the studies on the effect of Cu(II) salt addition to Cu(I) salt, solvent effects, and ESR spectra, it was concluded that alkoxycopper(II) species, formed by the oxidation of Cu(I) with molecular oxygen in alcohol–ethylenediamine solution, acted cooperatively with Cu(I) to increase the catalytic activity. The idea was also supported by the fact that the condensation was remarkably accelerated by the combination of Cu(I) and chloromethoxycopper(II). Reaction pathways including the alkoxo and halogen bridged Cu(I)···Cu(II) mixed valence complex are proposed and discussed.
The Molecular Structures of (t-Butyl)(chloro)[(−)-sparteine]magnesium(II) and Dichloro[(−)-sparteine]magnesium(II)
Authors: Kageyama Hiroyuki , Miki Kunio , Kai Yasushi , Kasai Nobutami , Okamoto Yoshio , Yuki Heimei 
Published: July 2006

Abstract
Crystals of t-BuMgCl–(−)-sparteine (1) belongs to orthorhombic system; P212121, a=25.689(6), b=10.030(2), c=7.942(2) Å, and Z=4; MgCl2–(−)-sparteine (2) also crystallizes in orthorhombic system; P212121, a=11.180(4), b=11.957(4), c=12.573(5) Å, and Z=4. Both structures were solved by the heavy atom method, and refined by the block-diagonal least-squares procedure; (1) R=0.098 for 1199 non-zero reflections and (2) R=0.091 for 1347 observed reflections. The Mg atom in each complex has a distorted tetrahedral geometry: (1) Mg–N=2.17(2) and 2.18(2), Mg–C=2.19(2), and Mg–Cl=2.332(7) Å and N–Mg–N=83.9(5)°; (2) Mg–N=2.150(9) and 2.160(9), and Mg–Cl=2.269(5) and 2.279(6) Å, and N–Mg–N=85.0(4)°.
Mass-spectrometric Measurements of Thermodynamic Properties of the Molten KCl–MnCl2 System
Authors: Sasamoto Tadashi , Itoh Mitsuru , Sata Toshiyuki 
Published: July 2006

Abstract
Activities and heats of mixing for the molten KCl–MnCl2 system were determined mass-spectrometrically by the ion-current ratio method. Activities of components KCl and MnCl2 show large negative deviations from Raoult’s law, indicating a very strong interaction between KCl and MnCl2. Entropies of mixing calculated from measured activities and heats of mixing have minimum values in the vicinity of 33% MnCl2, and have been compared with those calculated on the basis of some molten structure models to infer possible chemical species in the molten salt.
The Electrolytic Behavior of Tetrasubstituted Iminium Salt in Acetonitrile
Authors: Kunai Atsutaka , Harada Junji , Nishihara Masayasu , Yanagi Yasuo , Sasaki Kazuo 
Published: July 2006

Abstract
Cathodic behavior of N-cyclohexylidenepyrrolidinium salt (1) and N-cyclohexylideneaniline (2) in acetonitrile has been studied by means of dc polarography, cyclic voltammetry and preparative electrolysis under controlled potential conditions. The compound 1 exhibits a reduction wave at about −1.8 V, which is accompanied by formation of a surface compound. The products obtained from the preparative electrolysis were neither saturated amines nor dimeric compounds but were mostly polymeric materials. However, when electrophilic olefins, such as acrylonitrile or methyl acrylate, were present in the solution, coupling products were produced. The compound 2, which cannot be reduced by itself below −2.7 V, is reduced at about −1.8 V when benzoic acid is in the solution. The reduction product in this case was N-cyclohexylaniline, which was replaced by a coupling product when acrylonitrile was present in the reaction system. The formation of the coupling products is considered to occur by a radical mechanism in both cases.
Photochemical Dehalogenation of Polyhalobenzenes. I. Survey of the Reactivity in Hexane Solution
Authors: Nakada Masahiro , Fukushi Sachio , Nishiyama Hideaki , Okubo Keiji , Kume Kotaro , Hirota Minoru , Ishii Tetsuo 
Published: July 2006

Abstract
Photochemical dechlorinations and debrominations of C6HnX6−n (X=Cl, Br) isomers were carried out in hexane. The products and residual reactant were determined quantitatively by means of gas chromatography. From these experiments, the relative rates of dehalogenation were obtained. The different rates among unequivalent sites in a molecule were interpreted by the effect of steric acceleration by the neighboring halogen atom(s). The reactivity of the halogen atom in polyhalobenzene towards photochemical elimination reaction is dependent both on its position in the molecule when compared among isomers and on the number of halogen atoms in a molecule when compared among polyhalobenzenes of various degrees of substitution. The latter effect is more predominant in the series of polybromobenzenes.
A Facile One-pot Synthesis of Hydroxy-substituted Crown Ethers
Authors: Ikeda Isao , Katayama Tetsuya , Tsuchiya Kikuo , Okahara Mitsuo 
Published: July 2006

Abstract
Hydroxy-substituted crown ethers were prepared in one-pot synthesis by treatment of oligoethylene glycols with epichlorohydrin in the presence of alkali metals, alkali metal hydride or alkali metal hydroxides. The stability constants of complexes with sodium and potassium cations in methanol were determined.
Studies on the β-Turn of Peptides. IV. Effect of the Chain Length on the CD Spectra of N-(2,4-Dinitrophenyl)-(Gly)n–d-Ala–l-Pro–(Gly)n p-Nitroanilides (n=1–3)
Authors: Sato Kazuki , Taki Noriko , Nagai Ukon , Higashijima Tsutomu 
Published: July 2006

Abstract
N-(2,4-Dinitrophenyl)-(Gly)n–d-Ala–l-Pro–(Gly)n p-nitroanilides (7b, n=2; 7c, n=3) were synthesized in order to study the effect of chain length on their conformations. The CD spectra of both 7b and 7c snowed similar patterns to that of 7a (n=1), but their Cotton effects were much weaker. Therefore, both compounds seem still to have some populations of folded conformers because their Cotton effects near 350 nm were significantly larger than those of the tetrapeptide derivatives in random conformation. However, the population of the folded conformers must be quite small.
Nucleophilic Substitution on 4-Methylbenzyl Thiocyanate with Nucleophiles
Authors: Oae Shigeru , Yamada Norihiro , Fujimori Ken , Kikuchi Osamu 
Published: July 2006

Abstract
The reactions of 4-methylbenzyl thiocyanate (1) with several nucleophiles have been investigated. Compound 1 possesses three electrophilic sites, i.e., benzylic carbon, sulfur and cyano carbon, to receive nucleophilic attack. PhS− and CN− which have HOMO’s of high energy levels appear to attack preferentially the sulfur atom. MeO− was found to attack preferably the cyanide carbon, while amines which have HOMO’s of low energy levels prefer benzylic carbon to attack. The nucleophilic substitution on the sulfur or the cyanide carbon generates CN− or p-xylene-α-thiolate anion, strong nucleophiles, as the primary products, which then initiate the complex secondary reactions. The selective reactivities of three attacking sites for nucleophiles in 1 have been rationalized in terms of MO theory.
Glass-like Carbon Made from Epoxy Resin Cured with 2,4,6-Trinitrophenol
Authors: Kawamura Kazuro , Kimura Shiushichi 
Published: July 2006

Abstract
It has been found that a glass-like carbon can be produced by the slow and carefully controlled pyrolysis of the epoxy resin (Epikote 828) cured with 2,4,6-trinitrophenol (TNP) with a weight of 10–15%. The most characteristic property of the glass-like carbon was seen in its change in density with the heat-treatment temperature. Under heat treatment at temperatures up to 1000 °C, a dense glass-like carbon of which density was 1.65–1.70 g/cm3 was formed. The density of the glass-liken carbon decreased, however, at heat-treatment temperatures above 1000 °C. Upon heat treatment at the temperature of 3000 °C, the density dropped to a low value of 1.04–1.11 g/cm3. The former increase in density is connected with the large-scale dehydration reaction which may proceed between nitro groups and hydrocarbon chains in the cure resin. The latter decrease in density is caused by the progress of the graphitic orientation of carbon-layer planes in the cross-linked structure of the highest degree. If carbon fibers were present in this glass-like carbon, the graphitization of the glass-like carbon in the composite proceeded more easily than that of the glass-like carbon alone.
Photodimerization Mechanism of m-Methoxystyrene via Its Cation Radical. Open Type Dimer Cation Radical as Its Intermediate
Authors: Yamamoto Masahide , Yoshikawa Hiroaki , Gotoh Tetsuya , Nishijima Yasunori 
Published: July 2006

Abstract
Two isomeric tetralin type dimers were obtained by UV excitation of m-methoxystyrene in the presence of an electron acceptor. Stepwise electrophilic dimerization mechanism through the dimer cation radical was confirmed. The scheme was analyzed with the aid of MO calculation.
The Lithium Diisopropylamide-induced Fragmentation of 1,3-Dithiolane Derivatives of Several Ketones Having α-Hydrogen
Authors: Ikehira Hideyuki , Tanimoto Shigeo , Oida Tatsuo 
Published: July 2006

Abstract
The reaction of 1,3-dithiolane derivatives of ketones having α-hydrogen with lithium diisopropylamide results in fragmentation to the corresponding thioketone followed by further conversion in a few steps to the other intermediate species which, on trapping with alkyl halide, leads to a vinylic sulfide and/or a sulfide bearing a secondary alkyl group.
Intramolecular Stereospecific Pummerer Reactions of Aryl (Substitutedmethyl) Sulfoxides Bearing Electron-withdrawing Groups with Acetic Anhydride
Authors: Numata Tatsuo , Itoh Osamu , Yoshimura Toshiaki , Oae Shigeru 
Published: July 2006

Abstract
The Pummerer reaction of optically active cyanomethyl aryl sulfoxides with acetic anhydride gave the corresponding α-acetoxy sulfides which were induced with a partial asymmetry nearly 30% at α-carbon, while the 18O-label of the original sulfoxides was retained in more than 85% in the resulting ester, the Pummerer reaction product. Kinetic experiments with cyanomethyl (p-substituted phenyl) sulfoxides and α,α-dideuterated cyanomethyl p-tolyl sulfoxide in the reaction with acetic anhydride containing a small amount of acetic acid revealed that the rates were correlated with Hammett σ-values and ρ-value of −0.70 was obtained, while the kinetic isotope effect was practically nil, i.e., kH⁄kD=1.01. These observations indicate clearly that the rearrangement is intramolecular and proceeds via forming a very intimate ion-pair and the rate-determining step is believed to be the S–O bond cleavage after the initial reversible acylation and deprotonation. Elimination of acetic acid proceeds through the Elcb type process. The uneven distribution of 18O in the two oxygens of the resulted ester, i.e., ether and carbonyl oxygens, suggests the recombination of the α-sulfenyl carbonium ion and acetate ion to be very rapid. The Pummerer reaction of optically active N,N-dimethyl-p-tolyl-sulfinylacetamide with excess acetic anhydride also gave the corresponding α-acetoxy sulfide in optically active form. In the presence of dicyclohexylcarbodiimide (DCC), the Pummerer reaction was found to be highly stereoselective affording the corresponding α-acetoxy sulfide with 65%e.e. Other optically active α-carbonyl-substituted alkyl sulfoxides, i.e., ethyl p-tolylsulfinylacetate and ω-(p-tolylsulfinyl)acetophenone also gave the corresponding highly optically active Pummerer rearrangement products in the treatment with acetic anhydride/DCC system. The Pummerer reaction of the 18O-labeled sulfoxides with acetic anhydride/DCC system gave the corresponding α-acetoxy sulfides which retained much of the original 18O-labels of the sulfoxides. These observations reveal clearly that in the Pummerer reaction of these compounds the acetoxyl migration is intramolecular and takes place through intimate ion-pairs.
The Long-wavelength nπ* Phosphorescence Spectra of p-Quinones in Polycrystalline Solutions at 77 K
Authors: Kuboyama Akira , Kojima Yoshikuni , Matsuzaki Sanae Y 
Published: July 2006

Abstract
Besides the usual nπ* phosphorescence spectra, broad, long-wavelength nπ* phosphorescence spectra are observed in normal paraffine solutions, such as a heptane solution, of 1,4-naphthoquinone, and in a benzene solution of 5,14 : 7,12-pentacenediquinone at 77 K. The energy difference between the two spectra are ca. 750 and 980 cm−1 respectively. The intensity of the long-wavelength spectra relative to the short-wavelength spectra becomes weaker with decreases in the concentrations of the quinones, and the lifetimes of the long-wavelength spectra are shorter than those of the short-wavelength spectra. These long-wavelength spectra are assigned to those of the quinone aggregates. The excitation spectra of these phosphorescences have also been obtained. An explanation of the above red-shift of the nπ* phosphorescence spectra of the aggregates is presented; in it, the phosphorescence state of the aggregates corresponds to the nπ* triplet excimer state.
Laser-induced Fluorescence of the NaCs Molecule
Authors: Onomichi Kyoko , Katô Hajime 
Published: July 2006

Abstract
Laser-induced fluorescence of NaCs is observed when a mixture of sodium and cesium is irradiated by the 5682 Å laser line. The spectroscopic constants of the ground state X1Σ+ have been determined and the potential energy curve was calculated by the RKR method. The excited state was identified as D 1Π, and the potential curve was estimated from the analysis of the fluorescence intensities.
Synergistic Solvent Extraction of Crown Ether Complexes with Alkali Metal Picrates by Neutral Donor Solvents
Authors: Takeda Yasuyuki 
Published: July 2006

Abstract
The solvent extraction of rubidium and caesium picrates has been studied at 25 °C with mixtures of crown ether and tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) in benzene, and the adduct-formation constants in the benzene solution have been calculated. The crown ethers used in this work were 12-crown-4 (12C4), 15-crown-5 (15C5), and benzo-15-crown-5 (B15C5). The stoichiometric composition of any extracted complex under the present experimental conditions is alkali metal ion : crown ether : TBP or TOPO : picrate ion=1 : 1 : 1 : 1. The TOPO complex is more extractable than the corresponding TBP complex. The extractability of the Rb+ complex is larger than that of the corresponding Cs+ complex. For both TBP and TOPO, the adduct-formation constant value sequences of Rb+ and Cs+ are B15C5&gt;12C4&gt;15C5 and 12C4&gt;B15C5&gt;15C5, respectively.
Studies on Lanthanoids–Antimony–Chalcogenides. I. Synthesis and Crystal Data of Three New Lanthanum Antimony Chalcogenides
Authors: Gao Jin-zhang , Nakai Izumi , Nagashima Kozo 
Published: July 2006

Abstract
Three new La–Sb chalcogenides were synthesized by hydrothermal or evacuated silica tube methods. (1) LaSbO2S2: a bright-red needle crystal; crystal system, hexagonal; space group, P63/m; lattice constants, a=14.954(3), c=3.898(2) Å, and Z=6. (2) La6Sb8S21: a blackish-red columnar crystal with metallic luster, orthorhombic, P222, a=14.317(2), b=15.239(4), c=8.685(1) Å, and Z=2. (3) La3Sb3S10: a bright-red platelike crystal, monoclinic, a=13.209(6), b=14.229(6), c=5.583(1) Å, β=94.54(3)°, and Z=2.
Intermolecular Stereoselective Pummerer Reactions of 4-(p-Chlorophenyl)thiane 1-Oxides and trans-1-Thiadecalin 1-Oxides and 2-Thiadecalin 2-Oxides with Acetic Anhydride
Authors: Oae Shigeru , Itoh Osamu , Numata Tatsuo , Yoshimura Toshiaki 
Published: July 2006

Abstract
The Pummerer reactions of conformationally fixed 4-(p-chlorophenyl)thiane 1-oxides and trans-1-thiadecalin 1-oxides and trans-2-thiadecalin 2-oxides with acetic anhydride are either stereoselective or stereospecific, both in the absence and in the presence of a scavenger of acetic acid formed, such as dicyclohexylcarbodiimide (DCC) or 2,6-lutidine. However, the 18O-tracer experiments with the 18O-labeled sulfoxide revealed the reaction to be an intermolecular rearrangement, while the kinetic experiment with α-deuterated 4-(p-chlorophenyl)thiane 1-oxides gave sizable values of kinetic isotope effect, i.e., 2.8 for the cis isomer and 3.4 for the trans isomer. In the reaction of 4-arylthiane 1-oxides with acetic anhydride, the thermodynamically controlled product is axial 2-acetoxy-4-(p-chlorophenyl)thiane while the kinetically controlled product is the equatorial isomer which is formed in the presence of the acid scavenger, DCC. In the Pummerer reaction of the thiadecalins S-oxides the equatorial α-acetoxy sulfides are the preferential products, however, the isomer preference is more pronounced in the reaction with DCC. These observations, along with other pertinent data seem to suggest that the rate-determining step in the Pummerer reaction of these simple heterocyclic sulfoxides is E2 elimination of acetic acid from the acetoxysulfonium intermediates.
The Catalytic Cracking of Slack Wax with Molten Mixtures Containing Aluminum Chloride and Bromide
Authors: Ohtsuka Yasuo , Oizumi Kazutoshi , Tamai Yasukatsu 
Published: July 2006

Abstract
The catalytic cracking of slack wax with molten mixtures of AlCl3 and AlBr3 was investigated in an atmospheric semi-batch reactor at low temperatures of 100–160 °C. The cracking rate was proportional to the amount of unreacted wax. The conversion at 135 °C reached 25 wt% under typical reaction conditions. About 95 wt% of the cracking products consisted of isobutane, 2-methylbutane, and methylpentanes, ca. 50% of these isoparaffins being isobutane. The difference in cracking activity between this catalyst and a solid acid catalyst is discussed based on the product distribution. Hardly any reaction took place without HCl, which shows that the presence of HCl is essential for this cracking. The cracking rate increased sharply with an increase in the amount of the catalyst. The rate did not depend on the composition of the AlCl3–AlBr3 catalyst, but the product distribution did depend on it and the content of the gasoline fraction in the products increased with an increase in the concentration of AlBr3. The cracking residue was characterized by IR and NMR spectroscopy. The results show that the cracking reaction probably occurs heterogeneously at the interface between the liquid wax and the molten catalyst.
Synthesis, Characterization, and Crystal-structure Analysis of the 2:1 Molecular Complexes between 1,3,5-Trinitrobenzene and Copper(II), Nickel(II), or Palladium(II) Complexes with the Schiff Base Ligands Derived from o-Hydroxynaphthaldehydes and Monoamines
Authors: Matsumoto Naohide , Hara Tadanori , Hirano Akira , Ohyoshi Akira 
Published: July 2006

Abstract
The molecular complexes between 1,3,5-trinitrobenzene(TNB) and copper(II), nickel(II), or palladium(II) complexes with the Schiff base ligands derived from 1-hydoxy-2-naphthaldehyde or 2-hydroxy-1-naphthaldehyde and monoamines (RNH2: R=CH3, C2H5, n-C3H7, i-C3H7, n-C4H9) have been prepared and characterized. One of the molecular complexes bis(1-(isopropyliminomethyl)-2-naphtholato)palladium(II)-bis(1,3,5-trinitrobenzene) (Pd(2,1-i-C3H7)2·2TNB) has been subjected to the single-crystal X-ray analysis. Its crystal structure consists of alternately stacked donor (naphthalene moiety of the metal complex) and acceptor (TNB) molecules. The coordination geometry is a square planar with a markedly stepped chair-like shape, where the seat and the rests are formed by the coordination plane (PdO2N2) and two naphthalene moieties. The Pd atom is deviated by 0.62 Å from the least-squares plane of the naphthalene ring and the dihedral angle between the coordination plane and the naphthalene ring is 25.1°. When the crystal structure was viewed perpendicular to the donor or acceptor plane, the center of the TNB molecule coincides approximately the center of terminal benzene ring of the naphthalene moiety. Electronic spectra of the molecular complexes in Nujol mull showed a new band at about 18×103 cm−1, which was not observed in solution spectra.
Studies in Nickel(IV) Chemistry. V. Kinetics of Electron Transfer in Redox Systems Containing Tris(dimethylglyoximato)nickelate(IV), Hydroxylamine, and Catalytic Amounts of Copper(II) in Aqueous Alkaline Media
Authors: Acharya Sridhara , Neogi Gautam , Panda Rama Krushna , Ramaswamy Dorai 
Published: July 2006

Abstract
Kinetics of electron transfer in the redox system containing hydroxylamine and tris(dimethylglyoximato)nickelate(IV) ([Ni(dmg)3]2−), in the presence of catalytic amounts of added copper(II) ions, have been studied in aqueous medium in the pH range 8.04–11.81. The kinetics exhibit pseudo-zero-order disappearance of [Ni(dmg)3]2− when excess [NH2OH]0 is present, in the presence and absence of added metal ions. While addition of Cu(II) results in significant catalysis, that of Co(II)/Co(III), Fe(II)/Fe(III), Ni(II) or Zn(II) does not. The pseudo-zero-order rate constants (k0) are found to be linearly dependent on [NH2OH]0 and on added [Cu(II)]. The k0 values register a decrease as [OH−] is increased in the pH range 8.04–ca.9.42, attaining a limiting value in the pH range ca. 9.8–ca. 11.81. Results are interpreted in terms of a probable mechanism involving formation of precursor complexes from hydroxylamine and Cu(II) species, followed by rate-determining breakdown of the precursors with concomitant electron transfer. The Cu(II)·aq species reacts several orders of magnitude faster than the Cu(OH)2·aq species. The Ni(IV) does not appear to have any kinetic role in the redox system and is involved only in rapid product formation steps. The stoichiometric ratios (Δ[Ni(IV)]/Δ[NH2OH]) of ca. 1.0 in the lower pH region (7.8–8.6) and ca. 0.5 in the higher pH region (9.1–11.6) are explained in terms of differential product formation.
The Chemical Preparation of Tin Organosol
Authors: Ichiba Sumio , Ono Hiroaki , Kawasaki Shunji , Nakagawa Sakae , Yamada Masaaki 
Published: July 2006

Abstract
A stable colloidal tin suspension in an organic solvent was prepared by the chemical reduction of tin(II) chloride with sodium tetrahydridoborate in the presence of a protective agent. The tin organosol was examined by means of the Mössbauer absorption spectra of 119Sn in the frozen solution and by means of an electron microscope.