bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of Molecular Complexes of a Water-Soluble Porphyrin with Amino Acids: Importance of Hydrophobic Interaction
Authors: Tabata Masaaki , Shimada Akinobu 
Published: July 2006

Abstract
Amino acid interacts with 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine (H2TPPS4) to form molecular complex. The formation constants (logK) defined as HA+H2TPPS4\ightleftharpoonsHA·H2TPPS4 were found to be 2.00±0.05, 1.43±0.03, 0.83±0.02, −0.41±0.07, and −0.96±0.09 for l-tryptophan (Trp), l-tyrosine (Tyr), l-phenylalanine (Phe), l-leucine (Leu), and l-valine (Val) respectively, at 25°C and an ionic strength of 0.1 mol dm−3 (NaNO3), where HA denotes a neutral form of amino acid. The formation constants are linearly correlated to the hydrophobicity of the side-chain of amino acid: l-tryptophan exerts the largest interaction with porphyrin among them. Amino acids also interact with porphyrin adsorbed to an anion-exchange resin. Partition coefficient and retention volume were determined by batch and column methods using the porphyrin-loaded resin. The distribution coefficient and the retention volume of amino acid increase with the hydrophobicity of side-chain of amino acid. The formation of the molecular complex was also confirmed by 1H NMR spectra for H2TPPS4/Trp and H2TPPS4/Leu.
Preparation of Single Crystals of a New Compound, Ta5B6 by the Aluminium-Flux Method
Authors: Okada Shigeru , Hamano Kenya , Higashi Iwami , Lundström Torsten , Tergenius Lars-Erik 
Published: July 2006

Abstract
Single crystals of a new compound Ta5B6 was prepared by the high temperature aluminium solution method using tantalum and boron powder as starting materials in an argon atmosphere. The experimental conditions for obtained single crystals of relatively large size were established. The optimum conditions for growing Ta5B6 single crystals were found to include atomic ratios of starting materials B/Ta=1.2 and Al/Ta=8.38, soaking temperature 1650°C, soaking time 5 h and a cooling rate of 25°C h−1. Single crystals of Ta5B6, having a grey color and metallic luster, were generally obtained in the form of an irregular or trapezoidal shape: the latter crystals were enclosed by two large {010} planes. The largest crystals prepared have maximum dimensions of about 0.12mm×0.13mm×0.23mm. The crystals are orthorhombic with a space group of either Cmm2, Cm2m, C222, or Cmmm and the unit cell dimensions a=3.1385(10) Å, b=22.609(7) Å, c=3.2865(8) Å, and V=233.20(12) Å3. The X-ray density is 13.808(2) g cm−3. The present study of growing Ta5B6 crystals is the first single crystal growth study of a V5B6 type crystal.
Thermodynamics and Kinetics of Propidium Binding to Poly(A)·Poly(U) in Aqueous Solution
Authors: Sugimoto Naoki , Monden Noriko , Sasaki Muneo 
Published: July 2006

Abstract
The propidium binding to poly(A)·poly(U) has been investigated thermodynamically and kinetically in buffers containing different concentrations of NaCl at various temperatures. Free propidium had an absorption maximum at 493 nm, and this shifted to about 530 nm for propidium fully bound to poly(A)·poly(U) in all solutions. The association constant for the reaction was 1.42×106 mol−1 dm3 at 2.02×10−2mol dm−3 of Na+concentration, and about 26 times larger than that at 1.02 mol dm−3 Na+. The dependence of the association constants indicated the enthalpies for the reaction at the low and high Na+ concentrations were 39.8 and −8.3 kJ mol−1, respectively. The entropies were 251 and 63 J K−1 mol−1, respectively. These thermodynamical results suggested that the association reaction of propidium to poly(A)·poly(U) may play different behaviors at the low and high salt concentrations. Kinetic results by a micro stopped-flow method indicated that the propidium binding to poly(A)·poly(U) was a single step at the low Na+ concentration, while at the high Na+concentration it consisted of two steps which contained the slow unimolecular process after the binding step.
NMR Spectra of Organogermanium Compounds. IX. NMR Spectra and Molecular Mechanics Calculations of 1-t-Butylgermacyclohexanes
Authors: Takeuchi Yoshito , Tanaka Katsumi , Harazono Toshie , Yoshimura Shin 
Published: July 2006

Abstract
A variety of t-butylgermacyclohexanes was prepared and their 13C and 73Ge (when possible) NMR spectra were determined. It was estimated that the conformational energy of a t-butyl group bonded to germanium is about 1.3 kcal mol−1 by NMR data though the molecular mechanics calculations gave variable results depending on the parameter for germanium used; 0.33 kcal mol−1 by Allinger’s parameter while 1.23 kcal mol−1 by Ouellette’s parameter. The origin of this discrepancy was discussed. The molecular orbital calculations (MNDO) gave an intermediate value (0.60 kcal mol−1).
Thermal Decomposition of 2,2-Bis(t-butyldioxy)alkanes
Authors: Suyama Shuji , Watanabe Yasumasa , Sawaki Yasuhiko 
Published: July 2006

Abstract
The thermal decomposition of 2,2-bis(t-butyldioxy)propane (1a) has been studied in cumene. The activation parameters obtained by the thermolysis of la are ΔH\eweq=145.6kJ mol−1 and ΔS\eweq=47.3 J K−1 mol−1. The decomposition products of 1a are acetone, t-butyl alcohol, t-butyl hydroperoxide, t-butyl peracetate, t-butyl 1-methyl-1-phenylethyl peroxide, and bis(1-methyl-1-phenylethyl). The peroxyacetal cleaves homolytically at one of dioxy bonds to yield an intermediate alkoxyl radical with α-t-butyldioxy group, which decomposes subsequently to t-butyldioxyl and methyl radicals via β-elimination. The thermal decomposition of 2,2-bis(t-butyldioxy)butane and 2,2-bis(t-butyldioxy)-3-methylbutane have also been examined. Relative rates of β-elimination of radicals from alkoxyl radicals are concluded to be isopropyl: ethyl:t-butyldioxyl: methyl=133:33:7:1, revealing a facile scission of dioxyl radical.
57Fe-Mössbauer Spectroscopic Study of Ferrocenylruthenocene, [1](1,1′)Ferroceno[1](1,1′)ruthenocenophane, and Reaction Products with Some Oxidizing Agents
Authors: Watanabe Masanobu , Sano Hirotoshi 
Published: July 2006

Abstract
Ferrocenylruthenocene reacts with sulfuric acid–NH4BF4 to give a mono-oxidized diamagnetic ferrocenylruthenocenium BF4− salt, while it reacts with p-benzoquinon–BF3(Et2O) to give a trioxidized paramagnetic ferrocenylruthenocenium (BF4−)3 salt. Mössbauer parameters of the former salt are very similar to those of neutral ferrocenylruthenocene, suggesting that the structure of the salt is expressed as [Cp(C5H4)Fe(II)(C5H4)CpRu(III)–Ru(III)Cp(C5H4)Fe(II)(C5H4)Cp]2+(BF4−)2 with an antiferromagnetic Ru(III)–Ru(III) bond in the solid state. Well-dissolved quadrupole splitting (Q.S.) values observed for the latter salt (e.g., 0.61mm s−1 at 4.2 K) suggest the presence of a kind of intramolecular electronic effect of a ruthenocenium moiety on the Fe(III) in the ferrocenium moiety.
Transesterification of Benzyl Phenylacetate Using Polymeric Quaternary Ammonium Salt of 1,8-Diazabicyclo[5.4.0]undec-7-ene
Authors: Ishikawa Tomomichi , Ohsumi Yasuyuki , Kawai Tadashi 
Published: July 2006

Abstract
When benzyl phenylacetate was treated with aqueous alcohols in the presence of polymer-attached quaternary ammonium hydroxide (PCS–DBU) prepared from l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and chloromethylated polystyrene, the transesterification to methyl phenylacetate preceded the hydrolysis to phenylacetic acid. The characterization of this PCS–DBU resin was studied by comparison with other analogous resins. It was found that the PCS–DBU resin has the highest catalytic activity and the strongest attractive affinity to the substrate among the three resins studied in this work, and plays an important role in the formation of alkoxide ions by the reaction of alohols with the hydroxide ions above the resin, in the protection of the alkoxide ions against the attack of water molecules, and in the attraction of the substrate. These effects were attributed to the specific and planar bicyclic system of the DBU, including hydrophobic long alkylene groups, in addition to the lipophilic function of polymeric skeleton. The reaction could be explained in terms of the mechanism of phase-transfer catalysis.
Solid-Phase Synthesis of Steroidogenesis-Activator Polypeptide under Continuous Flow Conditions
Authors: Nozaki Sukekatsu 
Published: July 2006

Abstract
4-(Hydroxymethyl)phenoxymethyl copoly(styrene–1% divinylbenzene) resin beads loosely packed in a glass column were satisfactorily employed as a solid support for synthesis of a triacontapeptide, steroidogenesis-activator polypeptide, under the Fmoc strategy. Peptide sythesis was carried out in a continuous DMF flow without generation of any considerable back pressure. Change of volume of the resin bed in the column was monitored in the course of peptide elongation. After cleavage from the resin, the product was purified on HPLC to give the desired triacontapeptide in an overall yield of 39% based on the C-terminal amino acid linked to the resin.
Unimolecular Decomposition Rate Theory at the High Pressure Limit and Its Application to the Dissociations of Methanes and Ethanes
Authors: Kodama Sukeya 
Published: July 2006

Abstract
A rate theory for the thermal decomposition by a single bond fission at the high pressure limit was derived from the conceptions that the equilibrium between the active molecule and the activated complex is adiabatic and that the zero point energy difference between the molecule and the complex (ΔEz\eweq) participates in the entropy term of the rate constant (kd∞) and is not related to the enthalpy term. It was also proposed a method calculating kd∞ by replacing the vibrational state sum with the entropy term. The values of kd∞ for methanes and ethanes were calculated using the present theory and the Gorin activated complex model. From good correspondences between the experimental and calculated values, the values of ΔHf,298°(CH3(g))=143.2, D0(CH3–CH3)=393.0, and D0(CH3–H)=449.1 kJ mol−1 were obtained for the standard heat of formation and the chemical bond dissociation energy. The apparent activation energy for kd∞ decreases drastically by increasing of the reaction temperature. This fact means that the estimation of thermodynamic values from the apparent activation energy is not adequate. It was also found that the vibrational temperature in the complex is considerably higher than the reaction temperature by the contribution of ΔEz\eweq mainly. This result denotes that the chemical equilibrium constant cannot be evaluated from the ratio of kd∞⁄kc∞, where kc∞ means the high pressure limiting rate constant of the radical-radical recombination reaction.
Asymmetric Synthesis of α-Amino-β-hydroxy Acids Using a Chiral Pyridoxal-Like Pyridinophane–Zinc Complex as an Enzyme Mimic; Scope and Limitation
Authors: Ando Makoto , Watanabe Jun , Kuzuhara Hiroyoshi 
Published: July 2006

Abstract
A chelate complex (4) with high homogeneity was precipitated upon stirring a mixture of zinc(II) ion and a Schiff base produced from glycine and (R)- or (S)-15-formyl-14-hydroxy-2,8-dithia[9](2,5)pyridinophane, chiral pyridoxal-like pyridinophane. A four-coordinated zinc chelate complex was newly proposed as the structure of 4. Aldol condensations between 4 and several aldehydes were attempted at pH 10.0. Only small linear chain aldehydes, such as acetaldehyde and propionaldehyde, could react with 4 under these conditions to give the corresponding α-amino-β-hydroxy acid in the range of 27–77% enantiomeric excess.
Computational Study of the Isomerizations and Fragmentations of the Singlet and Triplet CH2CH2NH Diradicals
Authors: Fueno Takayuki , Yamaguchi Kizashi , Kondo Osamu 
Published: July 2006

Abstract
Pathways for the thermal unimolecular reactions of the CH2CH2NH diradicals, both singlet and triplet, have been investigated by ab initio MO calculations using 4-31G basis functions. The minimum-energy paths for possible isomerizations and fragmentations are traced by the SCF gradient procedure, and multireference double-excitation (MRD) CI calculations carried out for all the stationary structures located. The results of calculation show that the energetically most favorable unimolecular reaction possible to the triplet diradical is an α-hydrogen detachment giving rise to CH2=CH–NH (2A″), whereas that to the singlet diradical is a 1,2-hydrogen migration to give CH3CH=NH (1A′). The activation barrier heights calculated for the two processes are 103 and 74 kJ mol−1, respectively. It is concluded that, in the gas phase, CH3CN and HCN should be formed concurrently by the α-bond cleavages of the doublet radical CH3CH=N (2A′), which will arise most readily from the vibrationally hot CH3CH=NH (1A′).
On the Reaction of N-[(3-Oxo-2-cyclohexenyl)imino]triphenylphosphorane with α-Bromo Ketones and α,β-Unsaturated Ketones
Authors: Nitta Makoto , Soeda Hironobu , Iino Yukio 
Published: July 2006

Abstract
The thermal reaction of N-[(3-oxo-2-cyclohexenyl)imino]triphenylphosphorane with α-bromo ketones and α,β-unsaturated ketones underwent an enamine-type alkylation and a subsequent aza-Wittig reaction to give substituted 1,5,6,7-tetrahydro-4H-indol-4-ones and 7,8-dihydro-5(6H)-quinolinones albeit in modest yields.
Transylidation of Some Stabilized Bismuthonium Ylides
Authors: Suzuki Hitomi , Murafuji Toshihiro 
Published: July 2006

Abstract
Triphenylbismuthonium diacylmethanides underwent the copper(I)-assisted transylidation with dimethyl sulfide and triphenylarsine in benzene at room temperature, giving the corresponding sulfonium and arsonium ylides in moderate to good yields, but they failed to exchange the ylide functionality with triphenylphosphine in most cases and with triphenylstibine in all cases examined, decomposition leading to the C– or O-phenylation of 1,3-dicarbonyl portion being the major reaction that took place.
Theoretical Investigation of van der Waals Interaction Energy of Helium Trimer. Three-Body Effect
Authors: Ichihara Akira , Itoh Reikichi 
Published: July 2006

Abstract
Using an ab initio configuration interaction (CI) treatment, the He trimer interaction energy for the equilateral triangular configuration was calculated. The CI included all single and double electronic excitations (SD CI). The resulting three-body component was significantly larger than the third-order perturbation calculation.
ESR Study on Free Radicals Produced from Hexane by Vacuum-Ultraviolet Photolysis, Sensitized Photolysis, and γ-Radiolysis
Authors: Koizumi Hitoshi , Yamaguchi Takehito , Yoshida Hiroshi 
Published: July 2006

Abstract
The free radicals generated from polycrystalline hexane at 77 K by photolysis with vacuum-ultraviolet light, sensitized photolysis, and γ-radiolysis were compared with each others using the ESR method. The selectivity of radical formation was found to depend on the excitation method.
A Convenient Preparation of 3,5-Disubstituted 1,2,4-Selenadiazoles from Primary Selenoamides by Treatment with N-Bromosuccinimide
Authors: Shimada Kazuaki , Matsuda Yoichi , Hikage Shigeki , Takeishi Yoshiyuki , Takikawa Yuji 
Published: July 2006

Abstract
A convenient preparation of 3,5-disubistituted 1,2,4-selenadiazoles was achieved by treatment of various primary selenoamides with N-bromosuccinimide.
Synthesis of α-Amino Acids Containing a Cyclopropane Ring via Cobalt-Catalyzed Carbonylation-Amidocarbonylation of Cyclopropanemethanols
Authors: Amino Yusuke , Izawa Kunisuke 
Published: July 2006

Abstract
N-Acetyl-3-cyclopropylalanine and 2-acetamido-3-cyclopropylbutyric acid were prepared under cobalt-catalyzed amidocarbonylation conditions from cyclopropanemethanol and α-methylcyclopropanemethanol, respectively. The reaction has been estimated to comprise the in situ formation of aldehyde from alcohol by cobalt-catalyzed hydrocarbonylation followed by subsequent amidocarbonylation.
Oxidation of s-Alcohols with “Oxone” in Aprotic Solvents in the Presence of Wet-Aluminium Oxide
Authors: Hirano Masao , Oose Masaki , Morimoto Takashi 
Published: July 2006

Abstract
The oxidation of secondary aliphatic, alicyclic, and benzylic alcohols with Oxone in aprotic solvents in the presence of “wet-aluminum oxide” afforded the corresponding ketones in good yields under mild conditions.
Manganese(III) or Cobalt(III)-Mediated Oxidative Radical Reactions of Terminal Dienes. One-Pot Synthesis of Bis(dihydrofuran)s
Authors: Nishino Hiroshi , Yoshida Tomoaki , Kurosawa Kazu 
Published: July 2006

Abstract
The reactions of terminal dienes such as 1,4-pentadienes and 1,5-hexadienes with tris(2,4-pentanedionato)-manganese(III) ([Mn(acac)3]) gave α,ω-bis(dihydrofuryl)alkanes (abbreviated bis(dihydrofuran)s, hereafter) in good yields. The reactions with tris(2,4-pentanedionato)cobalt(III) ([Co(acac)3]) instead of [Mn(acac)3] yielded the same bis(dihydrofuran)s quantitatively. The dienes also reacted with ethyl 3-oxobutanoate in the presence of manganese(III) acetate ([Mn(OAc)3]) or cobalt(III) acetate ([Co(OAc)3]) to produce the corresponding bis(dihydrofuran)s. The reactions of 1,3-butadienes with the manganese(III) or cobalt(III) complexes afforded only mono(dihydrofuran)s and oxidative rearrangement products, but the corresponding bis(dihydrofuran)s were not formed. The reaction of 1,5-hexadienes with ethyl hydrogen malonate in the presence of [Mn(OAc)3] did not give bis-annulated products, but mono(γ-lactone)s in moderate yields. The synthetic applications and limitations of the bis(dihydrofuran)s formation are discussed.
Stereoselective Synthesis of (E)- and (Z)-2-Alkenyltrimethylsilanes from 1,2-Epoxy-1,3-bis(trimethylsilyl)propane
Authors: Shimizu Nobujiro , Imazu Sachiko , Shibata Fumihiro , Tsuno Yuho 
Published: July 2006

Abstract
Stereoselective synthesis of various (E)- and (Z)-2-alkenyltrimethylsilanes (RCH=CHCH2SiMe3; R=Me, Et, n-Bu, i-Pr, c-hexyl, t-butyl, and phenyl) has been accomplished by a reaction of 1,2-epoxy-1,3-bis(trimethylsilyl)propane with Grignard reagents (RMgX) followed by subsequent Peterson olefination reactions of resulting 1,2-bis(trimethylsilyl)-3-alkanols [RCH(OH)CH(SiMe3)CH2SiMe3]; the acid (BF3OEt2 or HClO4)-catalyzed olefination yields the (E)-isomer, while the base (KH or NaH)-induced olefination yields the (Z)-isomer in more than 95% stereochemical purity in most cases.
Electrochromism of Octacyanophthalocyanine Thin Film. Investigation by Means of in situ Visible and Raman Spectroscopies
Authors: Takeshita Kimiya , Aoyama Yuko , Ashida Michio 
Published: July 2006

Abstract
The electrochromism of an octacyanophthalocyanine (H2Pc(CN)8) thin film was investigated by in situ visible and Raman spectroscopies in acid and alkaline electrolytes. A new absorption band was observed in the range 700–900 nm of the visible spectra during a reduction of the film. The absorbance reached a constant value at 2 F mol−1 of the cathodic electricity in an alkaline electrolyte. The Raman spectra showed a spectral change in the vibration range which is attributed to the macrocycle and the isoindole moiety; hence, the reduction seems to occur in the azaporphyrin ring. From both the visible and Raman spectra, it was revealed that H2Pc(CN)8 was protonated at the nitrogens in positions 6,13,20,27 by electrochemical reduction. The protonated H2Pc(CN)8 shows absorption in the near-infrared region in both acid and alkaline electrolytes. The mechanism for the formation of protonated H2Pc(CN)8 is considered to be analogous to that of hydrogen evolution in alkaline electrolytes. Both the visible and Raman spectra were reversible during reoxidation.
Reaction Mechanism for Ozone Oxidation of Polyethylene as Studied by ESR and IR Spectroscopies
Authors: Yamauchi Jun , Yamaoka Akiyoshi , Ikemoto Kunji , Matsui Tetsuji 
Published: July 2006

Abstract
In a previous study of graft copolymerization of methyl methacrylate onto polyethylene oxidized with ozone, we clarified that ozone-oxidation reactions produce peroxyl radicals in polyethylene and that the graft copolymerization is assumed to start upon heating, through the decomposition of hydroperoxides which are converted from the peroxyl radicals. A series of reaction processes proposed for the ozone oxidation were examined from the viewpoint of the reaction rate. The time–dependent content of the peroxyl radicals was pursued by observing in situ ESR; the initial evolution rate of the peroxyl radicals and the decay rate after the ozone-stop were discussed on the basis of the proposed ozone-oxidation mechanism, leading to a good agreement between the experiment and theory. The amounts of hydroperoxide and carbonyl species determined from iodometry and the IR spectra, respectively, were also discussed with regard to the oxidation time, showing reasonable linear dependences.
Structural Study of Optical Resolution. XV. Chiral Discrimination of the Facial Isomer of the Tris((R,S)-1,2-cyclohexanediamine)cobalt(III) Cation with (R,R)-Tartrate Anion
Authors: Mizuta Tsutomu , Toshitani Kazuo , Miyoshi Katsuhiko 
Published: July 2006

Abstract
Crystal structures of the two diastereomeric salts of the title Δ complex cation with (R,R)-tartrate anion, Δ-fac-[Co(R,S-chxn)3](ClO4)(d-tart)·mH2O (1) and Δ-fac-[Co(R,S-chxn)3]Cl(d-tart)·nH2O (2) (R,S-chxn=(R,S)-1,2-cyclohexanediamine and d-tart=dextro-rotatory (R,R)-tartrate dianion), have been determined by single crystal X-ray diffraction techniques. The former crystal 1 is orthorhombic with the space group P22121, a=12.358(3), b=22.094(5), c=32.770(7) Å, and Z=12, while the latter 2 is trigonal with the space group P3121, a=15.367(7), c=26.208(4) Å, and Z=6. In 1 are found two similar face-to-face contact modes in both of which the d-tart2− ion directs its four almost coplanar O atoms to the complex along the C3 axis, and three of them, two alcoholic and one carboxylic, are triply hydrogen-bonded to the three N–H protons on one of the triangular faces of the Δ complex denoted as the Δ-cis RRR face, where R stands for the chirality of the carbon atom adjacent to the N–H group hydrogen-bonded to the d-tart2− ion. The other triangular face of the complex denoted as the Δ-cis SSS face is so crowded that only two O atoms of the d-tart2− ion are hydrogen-bonded to the face. In 2 is found one face-to-face contact mode in which the d-tart2− ion approaches the Δ complex similarly, but the three O atoms are each placed midway between two of the three N–H protons on the triangular Δ-cis RRR face to form three bifurcated hydrogen bonds to them, and the d-tart2− ion tactfully avoids the steric repulsion marginally by inclining its molecular plane a little relative to the triangular face at the least expense of the multiple hydrogen bonds to the face. Based on the assumption that the face-to-face contact mode found in 2 is the most probable interaction mode conceivable in solution, the elution order and separation factor obtained by ion-exchange chromatography for some related [Co(chxn)3]3+ complexes are rationally interpreted.
Application of the SPE Method to Organic Electrochemistry. XII. Lead Dioxide as a Mediator for Electrooxidation of Cinnamyl Alcohol on Pt–Nafion
Authors: Chen Zhen , Ogumi Zempachi , Takehara Zen-ichiro 
Published: July 2006

Abstract
Lead dioxide was examined as a mediator to oxidize cinnamyl alcohol on Pt–Nafion, and was compared with manganese dioxide. Lead dioxide was deposited into Pt–Nafion. The current efficiency for the formation of cinnamaldehyde reached 65% at room temperature, slightly lower than that in the case of using manganese dioxide. The production of cinnamic acid was more remarkable on Pb, Pt–Nafion than on Mn, Pt–Nafion because of the higher oxidation potential of the former. The mediatory action of both oxides was examined and compared with the activity in chemical oxidation using oxides produced separately. The oxidation of cinnamyl alcohol by lead dioxide was faster than that by manganese dioxide. Their mediatory action reflected their chemical activity for the oxidation.