bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mesomorphic Characteristics of Liquid Crystalline Esters p-Methoxyphenyl p-Alkoxycinnamates
Authors: Dave Jayrang S , Dhake K P 
Published: July 2006

Abstract
The newly synthesized homologous series p-methoxyphenyl p-alkoxycinnamates (I) can be compared with the series N-[p-(p-alkoxycinnamoyloxy)benzylidene] p-anisidines (II).1) All the homologues of both the series (I) and (II) from C1 to C18 are mesogens. In series (II) the first five members decompose due to high transitions at about 300 °C. With decrease in length of the molecules of series (I) than that of series (II), the overall transitions also decrease by about 150 °C. The first seven members in series (II) are nematogens; polymesomorphism begins from octyloxy homologue with the commencement of smectic mesophase and continues to be exhibited upto the last i.e. octadecyloxy homologue. In series (I) also the nematic phase is exhibited upto the heptyl derivative; the smectic phase commences from C8-member in the form of monotropic phase thereby exhibiting polymesomorphism upto the C14 homologue. The last two members of series (II) are smectogens. The odd-even effect is missing in series (II) whereas in series (I), it is seen upto the fifth homologue. In both the series, the N-I curves show a falling tendency— a criterion of high melting series. From textures’ point of view both the series have common features, the nematic phase is threaded when it is the only mesophase shown and homeotropic in polymesomorphic region, whereas the smectic mesophase is focal conic fan shaped of smectic-A variety. This series also yields interesting comparison with the series (III) p-nitrophenyl p-alkoxycinnamates4) and (IV) p-chlorophenyl p-alkoxycinnamates.5)
Mechanistic Study of Acid-Catalyzed Proton Exchange in Lactams
Authors: Wang Wei-hsien , Cheng Pai-hui , Huang Chiung-yi , Jong Yih-ling 
Published: July 2006

Abstract
The kinetics of acid-catalyzed proton exchange in N-methylacetamide and a series of lactams (5- to 8-membered ring) were studied. Kinetic data were observed by NMR line-broadening and computer simulation methods. The significant retardation in exchange rate constants of valerolactam and 2-azacyclooctanone is attributed to the high barrier of ring inversion in the N-protonation mechanism of lactams. It is concluded that the imidic acid mechanism is dominant in these two lactams. However, for lactams with much lower barrier of ring inversion, the acid-catalyzed proton exchange is via the N-protonation mechanism as predicted by the inductive effect.
Thermal Reactions of Toluene by Use of a Clusius-Dickel Type Thermal Diffusion Column as a Reactor
Authors: Kawakami Shigenobu , Gao Zhiming , Nakada Masahiro , Yamaguchi Tatsuaki 
Published: July 2006

Abstract
Thermal reactions of toluene were investigated in the temperature range from 1290 to 1410 K under atmospheric pressure in a Clusius–Dickel type thermal diffusion column. The main product of the reaction was benzene, the selectivity of which increased with the rise of reaction temperature, reaching over 50% under most of the reaction conditions studied. The reactions of toluene were characterized by two features; the high selectivity of benzene, and a remarkable change in the selectivity of benzene and bibenzyl with the change of toluene conversion. These two features should be attributable to the thermal diffusion and convection, which caused the hydrogen evolved during the reaction to concentrate around the heater, and subjected toluene to hydrogenolysis without adding hydrogen as a reactant. The experimental results with regard to the change in benzene selectivity can be explained qualitatively by the theories developed for the separation column.
Stability of Large Polycyclic Aromatic Hydrocarbons in the Diffuse Interstellar Medium
Authors: Aihara Jun-ichi , Ichikawa Hiroshi 
Published: July 2006

Abstract
Fragmentation patterns of polycyclic aromatic hydrocarbons (PAHs) observed in mass spectra support the view that sufficiently large compact PAHs have a large possibility of surviving long in the diffuse interstellar medium. Multivalent molecular cations of these PAHs are moderately aromatic.
SAXS Curve Shape Analysis of 2-Butoxyethanol Aqueous Solutions
Authors: Hayashi Hisashi , Udagawa Yasuo 
Published: July 2006

Abstract
Small-angle X-ray scattersing (SAXS) of 2-butoxyethanol aqueous solutions was measured over wide concentration and temperature ranges, and analyzed with polynomial expasion by taking up to the 4-th order term into consideration. It was shown that the mixing state was sensitively reflected in the higher order coefficient of the SAXS curve.
CD Spectral Diagnosis of Absolute Configuration of Tetrahedral or Pseudo-Tetrahedral Metal Complexes of Salicylideneiminates
Authors: Sakiyama Hiroshi , Okawa Hisashi , Oguni Nobuki , Katsuki Tsutomu , Irie Ryo 
Published: July 2006

Abstract
Circular dichroism spectra of tetrahedral or pseudo-tetrahedral metal complexes of chiral salycylideneaminates have been examined with respect to the absolute configuration about the metal ion. The CD couplet pattern associated with the azomethine π–π* transition differs from each other between the complexes of bidentate salicylideneaminates (class A) and the complexes of quadridentate salicylideneaminates (class B), but within each class the CD patern is well correlated with the absolute configuration around the central metal.
Kinetics and Mechanism of Anation of cis-[Ru(bpy)2(H2O)2]2+ Ion by 8-Quinolinol in Water-Ethanol Mixtures
Authors: Mallick Debnath , De Gouri Sankar 
Published: July 2006

Abstract
The anation kinetics of the title complex were investigated spectrophotometrically in 10% (v/v) ethanol–water mixtures and the following rate law has been proposed in the pH range 3.65–6.5.

where k1 is the water dissociation rate constant of the substrate complex, k−1 is the aquation and k2 is the ligand capturing rate constant of the five-coordinate intermediate [Ru(bpy)2(H2O)]2+. The activation parameters have been calculated and compared with other substitution reactions. Considering all the results, a dissociative mechanism has been suggested.
A Novel Skeletal Rearrangement of 2-Azabicyclo[2.2.1]hept-5-ene-3-carboxylic Acid Derivatives into 2-Oxabicyclo[3.3.0]-oct-7-en-3-ones under Acidic Conditions
Authors: Kobayashi Tomoshige , Ono Katsuhiko , Kato Hiroshi 
Published: July 2006

Abstract
The reaction of ethyl 2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate with aroyl chloride and the subsequent hydrolysis of the ester group provided 2-aroyl-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylic acid derivatives, which underwent a stereospecific rearrangement giving 4-aroylamino-2-oxabicyclo[3.3.0]oct-7-en-3-ones by treatment with trifluoroacetic acid. On the other hand, the reaction of 2-benzoyl-2-azabicyclo[2.2.1]hept-5-ene with trifluoroacetic acid in heated benzene afforded 1-[(benzoylamino)methyl]-1,3-cyclopentadiene which afforded a Diels–Alder cycloadduct with N-phenylmaleimide. A plausible mechanism for the rearrangement is presented.
Synthesis and Antimicrobial Activity of Bactenecin and Its Analogs
Authors: Uchida Yoshiki , Shindo Mitsuno 
Published: July 2006

Abstract
Bactenecin and four analogs were synthesized by Merrifield’s solid phase method. The antimicrobial activity and conformation of the synthetic peptides were studied by the microplate dilution of the synthetic peptides were studied by the microplate dilution method and CD spectroscopy, respectively. The results suggest that the original sequence and cyclic structure are important for the expression of the potent antimicrobial activity of bactenecin. The CD spectrum of bactenecin revealed a profile corresponding to that of the random coil conformation.
Intramolecular [2+2] Photocycloaddition. 14. Cycloreversion of Cyclophanes Possessing a Cyclobutane Ring at Their Tether
Authors: Nishimura Jun , Wada Yasuhiro , Sano Yukari 
Published: July 2006

Abstract
Thermal cycloreversion of ten cyclophanes possessing a cyclobutane ring at their tether was examined. The rates were affected not only by their strain but also by their structural characteristics, such as meta- or para-configuration. The relative rate difference covered a range of the order of 106.
The Effect of the CCl3F-Treatment on Wettability of Silica Glass Surface by Water and Organic Liquid
Authors: Kurosaki Akito , Okazaki Susumu , Nishiyama Yoshiyuki 
Published: July 2006

Abstract
The wettability of silica glass plate by water and some organic liquids was varied by vapor-phase treatment of the surface with CCl3F at temperatures higher than 450 °C. The critical surface tension γc of the treated surface was found to be about 49 dyn cm−1 (1 dyn = 10−5 N).
A Systematic Study on the Bakers’ Yeast Reduction of 2-Oxoalkyl Benzoates and 1-Chloro-2-alkanones
Authors: Sakai Takashi , Wada Kou , Murakami Takahiko , Kohra Kiichiro , Imajo Norihisa , Ooga Yukihiro , Tsuboi Sadao , Takeda Akira , Utaka Masanori 
Published: July 2006

Abstract
The bakers’ yeast reduction of a series of 2-oxoalkyl arenecarboxylates [R(C=O)CH2O(C=O)C6H4-p-X] (1a–f) (R = CH3 to n-C6H13; X = H) and the phenyl-modified derivatives (1g–l) (R = n-C5H11, X = OH, CH3, F, Cl, Br, or I) as well as 1-chloro-2-alkanones R(C=O)CH2Cl (6a–f) (R = CH3 to n-C6H13) were systematically investigated. The substrate specificities, configuration and %ee of the reduction products were found to be highly dependent on the length of the alkyl group (R) and the α substituent. Thus, the benzoates 1a–f gave optically active 2-hydroxyalkyl benzoates (2a–f) (R, configuration, %ee) (a: CH3, S, 99; b: C2H5, S, 98; c: C3H7, S, 26; d: n-C4H9, R, 55; e: n-C5H11, S, 15; f: n-C6H13, S, 63) in 11–91% yields. Among the modification experiments of the phenyl group, 1g–l, the p-iodo substituent markedly increased the ee from 15 to 71%, although the yield was rather lowered (22% yield). The reduction of α-chloro ketones 6a–f also gave optically active 1-chloro-2-alkanols (7a–f) [(R, configuration, %ee) (a: CH3, S, 83; b: C2H5, S, 54; c: C3H7, R, 49; d: n-C4H9, R, 80; e, n-C5H11, R, 65; f, n-C6H13, R, 41)] in 16–69% yields.
The Spectroscopic Properties and Organometallic Reactivities of Cobalt(III) Porphyrins
Authors: Setsune Jun-ichiro , Saito Yasushi , Ishimaru Yoshihiro , Ikeda Mitsuhiro , Kitao Teijiro 
Published: July 2006

Abstract
Chlorocobalt(III) porphyrins showed novel UV-vis and 1H NMR spectra in a non-coordinating solvent to suggest displacement of the cobalt out of the porphyrin plane toward the axial ligand in solution. They underwent insertion of alkynes into the Co–Cl bond to generate σ-(trans-2-chlorovinyl)cobalt(III) complexes. In a special case, novel [4+2]cycloaddition reaction between the Co–N–C(pyrrole-α)-C(meso) moiety of [CoIIICl(oep)] [oep = octaethylporphyrin dianion] and dimethyl acetylenedicarboxylate took place. The reaction behavior of chlorocobalt(III) porphyrins was compared with that of diaquaperchloratocobalt(III) porphyrins which also reacted with alkynes in the presence of 2,6-lutidine to give analogous σ-vinylcobalt(III) porphyrins with a 2,6-dimethyl-1-pyridinio substituent occupying the trans-β-position of the σ-vinyl group. While the methoxycarbonyl group of methyl propiolate was directed to the α side of these σ-vinylcobalt(III) complexes, the phenyl group of phenylacetylene was found to be directed to the α side of σ-(2-chlorovinyl)cobalt(III) porphyrin and to the β side of σ-[2-(2,6-dimethyl-1-pyridinio)vinyl]cobalt(III) porphyrin.
Radical Intermediates in the Thermal Decomposition of 1,1-Bis(t-butyldioxy)cyclohexane
Authors: Sugihara Yasushi , Watanabe Yasumasa , Kumura Hiromi , Nakamura Tomoyuki , Suyama Shuji , Sawaki Yasuhiko 
Published: July 2006

Abstract
The thermolysis mechanism of 1,1-bis(t-butyldioxy)cyclohexane (6) has been studied in solutions. The activation parameters obtained in cumene are ΔH≠ = 139.5 kJ mol−1 and ΔS≠ = 44.8 J K−1 mol−1, and the volatile products are t-butyl alcohol, t-butyl peroxyhexanoate, and 2,3-dimethyl-2,3-diphenylbutane along with minor products of acetone, cyclohexanone, and t-butyl 1-methyl-1-phenylethyl peroxide. The thermolysis of 6 in benzene gave acetone and t-butyl alcohol as major volatile products. The polyester of 2-hydroxyhexanoic acid was obtained both in cumene and benzene as a non-volatile product, and the yield was as high as 76% in benzene. These facts indicate that [1-(t-butyldioxy)cyclohexyl]oxyl radical (7) undergoes a facile ring-opening reaction yielding 5-(t-butyldioxycarbonyl)pentyl radical (8). The resulting radicals abstract hydrogen atoms either intra- or intermolecularly. The former reaction is predominant in the absence of good hydrogen donors, affording 2-hexanolide and ultimately the corresponding polyesters.
One-Step Hydroamidation of 2-Aza-1,3-pentadienes
Authors: Okamoto Hidenori , Kobutani Tadashi , Kato Shozo 
Published: July 2006

Abstract
Various N-(1-aryl-1-alkenyl)-2-chloroacetamides bearing alkoxymethyl or alkylthiomethyl group on amide nitrogen were synthesized by a one-step hydroamidation of 2-aza-1,3-pentadienes. Some N-(1-aryl-1-alkenyl)-2-chloroacetamides were found to have high herbicidal activities against upland farm weeds.
Action of Fatty Acid Esters of l-Ascorbic Acid as Antioxidants in Phosphatidylcholine Liposomal Membranes
Authors: Takahashi Mareyuki , Komuro Erika , Niki Etsuo , Tanaka Kunihiko 
Published: July 2006

Abstract
The antioxidant activities of saturated fatty acid esters of l-ascorbic acid were studied in the oxidations of soybean phosphatidylcholine liposomes in aqueous dispersions aiming at elucidating their action as antioxidants in the liposomal membranes, especially the effects of number and length of the fatty acid ester side chains at either 6- or both 5- and 6-positions. Ascorbic acid esters were found to act as radical-scavenging antioxidants in the oxidations initiated by either aqueous free radical attacking from outside of the membrane or by lipophilic radical generated within the membranes. They inhibited the oxidation cooperatively with α-tocopherol in the membranes and reduced the rate of α-tocopherol consumption, their sparing effects on α-tocopherol being greatest for the monoesters and for the esters with the shortest fatty acid chains within the diester group. It was concluded that the intramembrane and intermembrane mobilities of ascorbic acid esters decreased with increasing number and length of fatty acid chains.
The Reactions of Monoalkylthio- or Monoarylthio-Substituted Cyclopropenium Salt with Nitrogen Nucleophiles: Formation of Polyfunctionally Substituted Pyrroles or Pyrazoles
Authors: Yoshida Hiroshi , Utsumi Fumitaka , Suzuki Hideki , Ito Satoru , Sakashita Shin-ichi , Ogata Tsuyoshi , Matsumoto Kiyoshi 
Published: July 2006

Abstract
The reactions of monoalkylthio- or monoarylthio-substituted cyclopropenium salt (1) with a number of secondary amines were studied. The amines, such as N-methylaniline, yielded indenes, whereas N-alkyl- or N-arylbenzylamines gave 1-alkyl- or 1-aryl-2-phenylpyrroles in low-to-moderate yields, depending on the kinds of substituents of the amines and 1. The reaction with N-isopropylbenzylamine-α,α-d2 (i-PrNHCD2Ph) resulted in the formation of the 1-isopropyl-2,3,5-triphenylpyrrole-4-d, clearly indicating the intramolecular H-abstraction mechanism via vinylcarbene intermediates for the formation of pyrroles. The reaction of 1 with tosylhydrazones afforded the ring opend hydrazide, while with phenyl-, methyl-, and t-butylhydrazines gave 1,4,5-trisubstituted pyrazoles in small yields.
NMR Relaxation Studies for Sodium and Potassium Ions and Water Molecules in Concentrated Aqueous Solutions of Dibutyl Phosphate
Authors: Iida Masayasu , Hata Yukari 
Published: July 2006

Abstract
The hydration and alkali-ion binding of an aggregate of the dibutyl phosphate (DBP) ion in its isotropic aqueous solution were investigated by measuring the nuclear magnetic relaxation times for 17O of H2O, and 23Na and 39K of hydrated alkaline metal ions at various temperatures. The relaxation rates for the 17O of H2O showed that the rotational motion of the water molecule is more restricted in the sodium system than that in the potassium system. Arrhenius plots also showed that the activation energy for the relaxation rate of the water molecule is larger in the sodium system. The dependences of the longitudinal relaxation rates for the alkali ions on the DBP concentrations in these systems showed that the sodium ion has an enhanced tendency, over the potassium ion, to interact with the dibutyl phosphate ion and to form ion-aggregates.
Viscosity measurements showed that the appreciable restriction of the motion of the water molecules in DBP solutions corresponds to a great extent in the aggregation of DBP.
Fluorescence Spectra of 1-Naphthol During the Sol-Gel Process of a Mixed Aluminum-Silicon Alkoxide (Si : Al = 94 : 6)
Authors: Fujii Tsuneo , Mabuchi Toshiaki , Kitamura Hiroshi , Kawauchi Osamu , Negishi Nobuaki , Anpo Masakazu 
Published: July 2006

Abstract
The fluorescence and fluorescence-excitation spectra of 1-naphthol during sol to gel to xerogel transitions of a mixed solution comprising silicon and aluminum alkoxides (Si : Al = 94 : 6) catalyzed by a small amount of NaOH aqueous solution have been observed as a function of time. During the reaction of the system, the spectrum shifted to the red in the first stage and shifted to the blue in the next stage. This behavior reflects the changes of polarity and microviscosity of the matrix surrounding the doped 1-naphthol molecules during the sol to gel to xerogel transitions of the mixed metal alkoxide. The gelation occurred at 10 d. On the other hand, the most remarkable red-shift in the fluorescence spectrum was observed at 9 d. Comparing the fluorescence and fluorescence-excitation spectra of 1-naphthol in typical solvents with those of the sol–gel process, it has become apparent that a part of the doped 1-naphthol molecules in the ground state form a contact ion pair on the surface in cages of the prepared gel.
Surface Alkoxylation of Silicas by Mild Reactions with Alcohols
Authors: Shioji Shuhei , Tokami Kenjirou , Yamamoto Hideo 
Published: July 2006

Abstract
The surface alkoxylation reaction of silicas was investigated under mild reaction conditions with some low-molecular-weight saturated aliphatic alcohols. Silica gels and porous silica glass were treated with liquid alcohols using a Soxhlet extractor below their boiling points. The number of formed alkoxyl groups was examined by both thermal analyses and infrared spectra. It was shown that some of the surface hydroxyl groups were easily esterified to alkoxyl groups, even by contact with the alcohols under mild reaction conditions. The degree of alkoxylation was higher for the silica gels than for porous silica glass. The adsorption isotherms of methanol vapor at room temperature were measured on silica gel samples which were previously activated at various temperatures. The adsorption equilibrium strongly depends on the pretreated temperature. The surface methoxylation reaction took place not only on the surface hydroxyl groups, but also on the siloxane bridges, even at room temperature.
The Crystal Structures of Cyanide Metmyoglobins Reconstituted with Iron(III) Complexes of Porphyrin, 5,10,15,20-Tetramethylporphyrin, and 5,10,15,20-Tetraethylporphyrin
Authors: Sato Takao , Tanaka Nobuo , Moriyama Hideaki , Matsumoto Osamu , Takenaka Akio , Neya Saburo , Funasaki Noriaki 
Published: July 2006

Abstract
The structures of three mimic myoglobins reconstituted with synthesized iron(III) meso-substituted porphyrins have been studied by X-ray crystallography. Although the overall structure of each globin was the same as that of the native, apart from a few terminal residues, the Cα atom of Arg45 in each crystal was displaced by 2.7 Å from that in the native. This large displacement opens a channel for the ligand penetration, formed by His64, Thr67, Val68, and heme. The movement of each porphyrin was estimated from the refined anisotropic temperature factors of its atoms, which showed that the root-mean-squares amplitude of the vibration about the normal to the porphyrin plane was significantly larger than the globin’s movement.
Simulation of Vibrational Spectra of Acetic Acid By an Extended Molecular Mechanics Method and Half Band Width Parameters
Authors: Yokoyama Isao , Miwa Yoshihisa , Machida Katsunosuke 
Published: July 2006

Abstract
The molecular mechanics simulation of the infrared absorption and Raman spectra of acetic acid in the solution or liquid phase has been carried out by using an empirically estimated force field which includes the equilibrium charges and the charge fluxes as the Coulomb potential parameters. The variation of the observed band widths among different normal modes has been taken into account by introducing the half band width parameters empirically assigned to individual internal coordinates. The half widths of more than 20 bands observed in the infrared absorption and the Raman spectra are well reproduced in terms of five half band width parameters. The thermodynamic properties and the structures of acetic acid monomer and dimer are successfully simulated. The overall features of the simulated spectra of acetic acid are in good agreement with the observed ones.
“Syn-Effect” in the Conversion of (E)-Vinylic Sulfones to the Corresponding Allylic Sulfones
Authors: Hirata Takaki , Sasada Yoshihiro , Ohtani Takashi , Asada Takahiro , Kinoshita Hideki , Senda Hitoshi , Inomata Katsuhiko 
Published: July 2006

Abstract
It was found that (E)-vinylic sulfones preferentially afford (Z)-allylic sulfones as kinetically-controlled products by treatment with a base under mild conditions, while (Z)-vinylic sulfones give (E)-allylic sulfones. Such stereochemical relationship was rationalized by “syn-effect”, and its relative degree for various substituents was determined by observation of E/Z ratios of the allylic sulfones resulted from the corresponding γ-mono- or γ,γ-disubstituted vinylic sulfones as follows: RO– (R = CH3, C2H5) ArO– (Ar = p-CH3OC6H4, p-CH3C6H4, C6H5, p-NO2C6H4) ≥ AcO– &gt; Cl– ≥ Br– &gt; CH3– &gt; CH3S– ≥ –CH2– (cyclic and acyclic) &gt; (CH3)2CH– &gt;&gt; (CH3)3C–, C6H5–. X-Ray crystallography was performed for some vinylic sulfones to reveal the origin of the “syn-effect”.
Solvent Extraction of Divalent Metals as Dihydrobis(1-pyrazolyl)borate Chelates
Authors: Yasuda Noriyasu , Kokusen Hisao , Sohrin Yoshiki , Kihara Sorin , Matsui Masakazu 
Published: July 2006

Abstract
The extraction behavior of divalent metals (M2+) with dihydrobis(1-pyrazolyl)borate ligand (H2B(pz)2−) has been studied. Divalent transition metals form [M{H2B(pz)2}2] chelates readily and are extracted into the organic phase. The extraction constants of the first-row transition metals increase in the order Mn(II) &lt; Fe(II) &lt; Co(II) &lt; Ni(II) &lt; Cu(II) &gt; Zn(II), which is in accordance with the Irving and Williams’ order for complex stability. Although Be2+ is slightly extracted by H2B(pz)2−, Mg2+, Ca2+, Sr2+, and Ba2+ are not extracted, whether a synergistic agent such as trioctylphosphine oxide and tetrabutylammonium chloride is added or not. The characteristics of H2B(pz)2− in the extractability of metal ions are ascribed to that the basicity of coordinating nitrogen atoms is increased by negative charge of the molecule and inductive effect of the boron atom, and that adduct formation is restricted by the steric hindrance.