bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Phase Transition of 1,4-Dialkyl-1,4-diazoniabicyclo[2.2.2]octane Dibromides, Cn–DABCO–Cn+1–Br2 (10≤n≤17)
Authors: Imamura Kengo , Nogami Takashi , Shirota Yasuhiko 
Published: July 2006

Abstract
The phase transitions of 1,4-dialkyl-1,4-diazoniabicyclo[2.2.2]octane dibromide (bis(quaternary alkyl bromide salts) of DABCO) in which the difference in the carbon numbers of the two alkyl groups is one, were studied on the basis of measurements of differential scanning calorimetry, infrared absorption spectroscopy, and bromide-anion conductivities. The DSC measurements showed that an endothermic transition occurred at Tc1 when the sample was heated from room temperature. An exothermic transition occurred at Tc2(Tc2&lt;Tc1) when the sample was cooled after it had been heated above Tc1. The transition temperatures (Tc1 and Tc2), the transition enthalpies, and the transition entropies increased as the increase in the alkyl-chain lengths. Tc1 was found to be governed by the even numbers of the alkyl group. The temperature dependence of the IR absorption spectra showed that the trans-zigzag conformation of the alkyl chain was destroyed by a conformational change above Tc1, and that the annealed sample existed as a metastable phase. The temperature dependence of the bromide-anion conductivities showed abrupt increases in the conductivities by three orders of magnitude at around the transition temperatures. The temperatures of the conductivity jump of the virgin samples were usually higher than those of the annealed samples. The differences in these two temperatures tended to become smaller as the increase in the alkyl-chain lengths. This fact can be explained as that the solid-state properties of the unsymmetric bis(quaternary salts) of DABCO tend to resemble those of the symmetric bis(quaternary salts) of DABCO as the increase in the alkyl-chain lengths.
A Molecular Orbital Study of the Electronic Structure of Some 6-Substituted Uracils
Authors: Abdul-Ahad Paul George , Webb Graham Alan 
Published: July 2006

Abstract
Semiempirical molecular orbital calculations are performed on a series of 28 6-[2-(substituted phenyl)hydrazino]uracils. Approximate ground state electronic properties are obtained for each molecule studied as well as the electrostatic potentials. First and second order interaction energies are calculated for some selected point charges in the vicinity of the parent molecule. The best correlations obtained between the biological activity and the electronic and steric indicies are considered in a mechanistic context.
Spectrophotometric Determination of Palladium(II), Osmium(VIII), and Iridium(III) with 2-Methyl-1,4-naphthoquinone 4-Oxime
Authors: Shravah Kamini , Sindhwani Sharwan Kumar 
Published: July 2006

Abstract
2-Methyl-1,4-naphthoquinone monoxime (MNQM) forms yellow-colored 1:1 (M:L) complex with palladium(II) and brown-colored 1:2 complex with osmium(VIII) and iridium(III). The complexes are insoluble in water but soluble in 1-butanol. The reagent has been used for the spectrophotometric determination of Pd(II), Os(VIII), and Ir(III). The palladium, osmium, and iridium complexes have maximum absorption at 460, 460, and 450 nm respectively with the sensitivity of 0.012 μg Pd/cm2, 0.025 μg Os/cm2, and 0.014 μg Ir/cm2 for logIo⁄I=0.001. The optimum concentration ranges for the determination of Pd(II), Os(VIII), and Ir(III) are 1.58–10.47, 3.02–23.99, and 1.6–11.5 ppm over the pH range 6.5–7.8, 6.5–7.7, and 5.9–7.3 respectively. The determinations have also been carried out in the presence of foreign ions. MNQM reacts with palladium(II) or osmium(VIII) or iridium(III) to form yellow- or brown-colored precipitates which are extractable in 1-butanol. These systems have been studied spectrophotometrically to determine the composition and other physical constants of the complexes. The possibility of determining Pd(II) or Os(VIII) or Ir(III) in presence of diverse ions has also been investigated. Palladium(II) and osmium(VIII) have been successfully determined in synthetic solutions corresponding to the alloys.
A Structural Model for Octacalcium Phosphate–Succinate Double Salt
Authors: Mathew Mathai , Brown Walter Eric 
Published: July 2006

Abstract
A new structural model for octacalcium hydrogenpentakis(phosphate) succinate pentahydrate, Ca8H(PO4)5(C2H4·(COO)2)·5H2O, a reaction product of octacalcium dihydrogenhexakis(phosphate) pentahydrate, Ca8H2(PO4)6·5H2O, OCP, and succinate ions, is proposed on the basis of similarities in the unit cell dimensions and structures of OCP and calcium succinate trihydrate. This model can be used to develop information on the mode of incorporation of dicarboxylate ions into OCP and hydroxyapatite and its possible effects on biological mineralization processes.
Influence of Pressure on the Menschutkin-Type Reaction of Phenethyl Arenesulfonates with Pyridine
Authors: Yoh Soo-Dong , Park Jong-Hwan , Lee Kyung-A , Han In-Sook 
Published: July 2006

Abstract
Kinetic investigation of β-phenylethyl arenesulfonates with pyridine in acetonitrile revealed that the rates of these reactions which were lower than those of the reaction of benzyl benzenesulfonate with pyridine in acetone were increased with raising temperatures and pressures. The activation volumes were comparable to those of benzyl system, but activation entropies were negatively larger than those of benzyl system. From these phenomena it can be deduced that phenethyl system has more SN2 character in the transition state, comparing with the reaction of benzyl system. With raising pressures the Hammett reaction parameters (ρ) were decreased, indicating that the reaction is probably closer to tight SN2 character at higher pressures.
Bis[perfluoro(1,1-dimethylbutyl)] Trisulfide from the Cesium Fluoride-Assisted Reaction of Hexafluoropropene Dimers with Disulfur Dichloride
Authors: Suzuki Hitomi , Satake Hiroshi , Uno Hidemitsu , Shimizu Hiroaki 
Published: July 2006

Abstract
Perfluoro(1,1-dimethylbutanide) anion generated from hexafluoropropene dimers and cesium fluoride in N,N-dimethylformamide, reacts with disulfur dichloride to give the title trisulfide as the predominant product.
A Convenient Synthesis of Hypotensive (±)-Oudenone
Authors: Sakai Takashi , Iwata Kohji , Utaka Masanori , Takeda Akira 
Published: July 2006

Abstract
(±)-Oudenone, 2-(tetrahydro-5-propyl-2-furylidene)-1,3-cyclopentanedione, was conveniently synthesized by BF3-catalyzed acylation of 1,3-cyclopentanedione with 4-chloroheptanoic anhydride and subsequent cyclization with triethylamine in a 36% overall yield.
Ester Aminolysis in the Presence of Alkylammonium Carboxylate Reversed Micelles. A Mechanistic Study
Authors: El Seoud Omar A , Vieira Rita C , Novaki Luzia P 
Published: July 2006

Abstract
A study of ester aminolysis in the presence of dodecylammonium carboxylate reversed micelles showed that the catalytic role of the surfactant head-anion (general base) was concentration independent. The presence of cosolubilized water in the micelle did not lead to detectable ester hydrolysis.
Effects of Alkyl Chain Length on Molecular Interactions. II. Complex Isomerism in the Alkyl p-Aminobenzoate-Picric Acid Systems
Authors: Togashi Atsushi , Matsunaga Yoshio 
Published: July 2006

Abstract
While a combination of p-aminobenzoic acid and picric acid gives a yellow-colored salt by proton transfer, the esterification of the former component compound with methyl to octadecyl groups results in the formation of not only stable salts but also metastable charge-transfer complexes.
Ylide–Metal Complexes. XII. The Preparation and Properties of Au, Be, Al, Ga, and In Complexes with Dimethylsulfoxonium Methylide
Authors: Yamamoto Yoshihisa 
Published: July 2006

Abstract
The reaction of dimethylsulfoxonium methylide, (CH3)2\overset+S(O)–\bar\"{C}H2 (L), with (triphenylphosphine)gold chloride, (C6H5)3PAuCl, yields a new bis(dimethylsulfoxonium methylide)gold(I) chloride, [(CH3)2S(O)CH2AuCH2S(O)(CH3)2]Cl. The reaction of the ylide L with BeCl2 yields a new compound of tetrakis(dimethylsulfoxonium methylide)beryllium dichloride, [(CH3)2S(O)CH2]4BeCl2. The reactions of the ylide L with AlCl3, GaCl3, and InCl3 yield new dimeric compounds of μ-chlorobis[tris(dimethylsulfoxonium methylide)metal] pentachloride, [{(CH3)2S(O)CH2}3M–Cl–M{CH2S(O)(CH3)2}3]Cl5 (M: Al, Ga, and In). All complexes are thermally stable.
Stereochemistry of the (Iminodiacetato or N-Methyliminodiacetato)(ethylenediamine-N-acetato)cobalt(III) Complexes
Authors: Ama Tomoharu , Niiyama Ryuichi , Kawaguchi Hiroshi , Yasui Takaji 
Published: July 2006

Abstract
Four geometrical isomers of [Co(mida)(edma)] were prepared in the first time and their structures were determined on the basis of their visible and UV absorption spectral data. Three of the isomers were optically resolved by the use of a column containing QAE-Sephadex of the Sb2(d-tart)22− form. Absolute configurations of the facially chelated isomers of [Co(mida)(edma)] were determined by measuring the 1H NMR spectra of the optically resolved isomers with an asymmetric carbon-containing edma (obtained from the stereospecifically deuterated (−)543CD C2-trans(O)-[Co(edma)2]2+). Absolute configuations of the facially chelated isomers of [Co(ida)(edma)] were determined on the basis of their CD spectral data.
Kinetics of Aquation of Pentaammineglycinerhodium(III) Ion in Acidic Media
Authors: Chatterjee Chinmay , Bali Aya Singh 
Published: July 2006

Abstract
Acid-catalyzed aquation of pentaammineglycinerhodium(III) ion has been studied kinetically in aqueous perchloric acid media (0.05–0.45 mol dm−3) over a temperature range of 60–80 °C at an ionic strength of 1.0 mol dm−3 adjusted with sodium perchlorate. Under these conditions the reaction occurs by two concurrent paths according to the rate law: Rate=ko[complex]+kH+[complex][H+], where ko and kH+ are the rate constants for the spontaneous and acid-catalyzed pathways, respectively. Analysis of rate data suggests cleavage of metal–oxygen bond in the rate determining step for both the processes.
Crystal Structures of Bis(r-1,c-3,c-5-cyclohexanetriamine)cobalt(III) Iodide and Tricyano(r-1,c-3,c-5-cyclohexanetriamine)cobalt(III) Monohydrate
Authors: Ishii Minoru , Umehara Michiko , Nakahara Masayoshi 
Published: July 2006

Abstract
The crystal structures of bis(r-1,c-3,c-5-cyclohexanetriamine)cobalt(III) iodide (1) and tricyano(r-1,c-3c-5-cyclohexanextriamine)cobalt(III) monohydrate (2) were determined by the X-ray diffraction technique. 1 is monoclinic with space group A2⁄a, a=10.437(2), b=16.131(2), c=12.486(2) Å, and β=94.36(3)°, and 2 is orthorhombic with space group Pbca, a=12.599(1), b=16.818(2), and c=11.659(1) Å, the final R values for 1 and 2 were 0.048 and 0.045, respectively. In both the complexes, all six-membered chelate rings formed by the r-1,c-3,c-5-cyclohexanetriamine ligand and central cobalt atom assume chair conformations. The presence of the six-membered chelate rings does not introduce, much distortion on the octahedral geometry of the chromophores. These findings are in fair agreement with spectroscopic data on these complexes.
Stereochemical Properties of Copper(II) Complexes of (S)-3-Aminohexahydroazepine. Crystal and Molecular Structure of Bromobis[(S)-3-aminohexahydroazepine]copper(II)Perchlorate [CuBr(S-ahaz)2]ClO4
Authors: Saburi Masahiko , Miyamura Kazuo , Morita Masatoshi , Mizoguchi Yasuo , Yoshikawa Sadao , Tsuboyama Sei , Sakurai Tosio , Tsuboyama Kaoru 
Published: July 2006

Abstract
A series of copper(II) complexes of (S)-3-aminohexahydroazepine (abbreviated as S-ahaz) were prepared. The molecular structure of bromobis[(S)-3-aminohexahydroazepine]copper(II) perchlorate, [CuBr(S-ahaz)2]ClO4, was determined using single-crystal X-ray diffraction method. The complex crystallizes is space group P212121 with a=13.449(6), b=17.411(11), c=7.937(2) Å, and Z=4. The structure was solved by the direct method and refined by the least squares to R value of 0.068 for 1853 unique reflections. The Cu2+ ion has the square-pyramidal five-coordination geometry with four nitrogen atoms as basal donors and a bromide as an apical donor. The structures of other copper(II) complexes of S-ahaz were assigned on the basis of the above X-ray analysis result, together with electronic spectral and conductivity measurements. The complexes having the formula Cu(S-ahaz)2X(ClO4) (X−=CI−, I−, NCS−, ONO−) were assigned to have square-pyramidal five-coordinated structures. The S-ahaz complexes Cu(S-ahaz)2X2 (X−=Cl−, Br−, NO3−) were also considered to have similar five-coordination geometries, while the complexes Cu(S-ahaz)2X2 (X−=ClO4−, BF4−) to be four-coordinated in the crystalline state.
Reactions of 3-(2-Methyl-1,3-dioxolan-2-yl)tropolone Methyl Ethers with Hydrazines, Thiourea, Guanidine, and Amidines
Authors: Imafuku Kimiaki , Kikuchi Yosuke , Yin Bing-Zhu 
Published: July 2006

Abstract
3-(2-Methyl-1,3-dioxolan-2-yl)tropolone, prepared from 3-acetyltropolone, was methylated with diazomethane to afford 2-methoxy-3-(2-methyl-1,3-dioxolan-2-yl)tropone (3a) and 2-methoxy-7-(2-methyl-1,3-dioxolan-2-yl)tropone (3b). The methyl ether 3a reacted with hydrazine to afford 2-hydrazono-3-(2-methyl-1,3-dioxolan-2-yl)-3,5-cycloheptadien-1-one and 3-methyl-1,8-dihydrocycloheptapyrazol-8-one. The reaction with methylhydrazine afforded 3-(2-methyl-1,3-dioxolan-2-yl)-2-methylhydrazono-3,5-cycloheptadien-1-one and 1,3-and 2,3-dimethyl-dihydrocycloheptapyrazol-8-ones. Another methyl ether 3b reacted with hydrazine to afford 2-hydrazino-7-(2-methyl-1,3-dioxolan-2-yl)tropone, while the reaction with methylhydrazine gave 2-(2-methyl-1,3-dioxolan-2-yl)-7-(2-methylhydrazino)tropone, 2-(2-methyl-1,3-dioxolan-2-yl)-7-(1-methylhydrazino)tropone, and 1,3-dimethyl-8-methylhydrazono-1,8-dihydrocycloheptapyrazole. On the other hand, the methyl ether 3a reacted with guanidine, acetamidine, and benzamidine to give 4-(2-methyl-1,3-dioxolan-2-yl)-2-amino-, 2-methyl-, and 2-phenylcycloheptimidazole, respectively. The reaction of the methyl ether 3b also gave the same products. The reaction of 3b with thiourea afforded 2-mercapto-4-(2-methyl-1,3-dioxolan-2-yl)cycloheptimidazole but 3a resulted in the rearrangement to ethyl 2-(2-methyl-1,3-dioxolan-2-yl)benzoate.
Racemization of Mandelic Acid at the Surface of Talc Powder
Authors: Ikekawa Akiko , Hayakawa Sohachiro 
Published: July 2006

Abstract
The addition of talc powder in an ethanolic solution of mandelic acid gave a large change of its optical rotation. It was confirmed by absorption spectrography, thin-layer chromatography, and gas chromatography that mandelic acid was racemized at the surface of the talc powder. The IR spectra showed that racemization took place when mandelate anions adsorved weakly at the surface of the talc. It was concluded that the H atom at the C atom in the second position of a mandelate anion was adsorbed at a basic site of the talc surface to deprotonate and also that the deprotonation was enhanced by the interaction between the carboxyl group and an acidic site.
Effect of Cationic Charge in Electrolyte-Amphoteric Ion-Exchange Membrane System
Authors: Hirata Yutaka , Date Masashi , Yamamoto Yukiko , Yamauchi Akira , Kimizuka Hideo 
Published: July 2006

Abstract
In order to clarify the membrane phenomena in an amphoteric membrane, four different experiments were carried out in a simple electrolyte-amphoteric membrane system. The ion transport numbers obtained from the membrane potential and electrodialysis were approximately in agreement with each other. It was indicated that the transport numbers strongly depended on the ionic valence in electrolyte solution. The membrane permeability coefficient representing the dynamic behavior of ion within membrane was evaluated in terms of membrane potential, transport number, and membrane conductance. In addition, the ionic concentrations within membrane equilibrated with outer electrolyte solution were measured to obtain the mobilities within membrane. The membrane phenomena were discussed on basis of the present experimental results.
Synthetic Inorganic Ion-Exchange Materials. XXXXVI. Ion-Exchange Behavior of Titanium(IV) Antimonate Cation Exchanger for Alkali Metal Ions in Ammonium Nitrate Media
Authors: Chitrakar Ramesh , Abe Mitsuo 
Published: July 2006

Abstract
Titanium(IV) antimonate (TiSbA) showed an extremely high selectivity for lithium ions in ammonium nitrate media, the increased selectivity order for microamounts being Rb+&lt;Na+&lt;Cs+&lt;K+&lt;&lt;Li+. The selective separation of lithium ions from other alkali metal ions can be achieved on small columns of TiSbA by a mixed solution of nitric acid and ammonium nitrate.
(Acetylacetonato)(N,N,N′,N′-tetramethylethylenediamine)copper(II) Tetraphenylborate as a Solvent Basicity Indicator
Authors: Soukup Rudolf Werner , Sone Kozo 
Published: July 2006

Abstract
The title complex, [Cu(acac)(tmen)]BPh4, is a color indicator for solvent basicity which serves better than the corresponding perchlorate in very weak donor solvents owing to its reluctance in ion-pair formation. The complex cation [Cu(acac)(tmen)]+ decomposes in very strong donor solvents, but these indicators may still be used in them with some care.
Light-induced Electron-transfer Reactions. 5. Kinetics of the Oxidation of Ethylenediaminetetraacetatocobaltate(II) Complexes by Peroxodisulfate Ion, Induced by Irradiation with Visible Light of Aqueous Solutions Containing Tris(2,2′-bipyridine)ruthenium(II) Ion
Authors: Nishida Suzuko , Kimura Masaru 
Published: July 2006

Abstract
The oxidation reaction of ethylenediaminetetraacetatocobaltate(II) ([Co(edta)]2−) by peroxodisulfate ion (S2O82−) is greatly accelerated by irradiation with visible light of aqueous solutions containing tris(2,2′-bipyridine)ruthenium(II) ion ([Ru(bpy)3]2+). The overall reaction is 2[Co(edta)]2−+S2O82− →2[Co(edta)]−+2SO42−. The [Ru(bpy)3]2+ ion acts as a photosensitizer and -catalyst for this reaction, and the mechanism consists of a chain reaction being initiated by the quenching reaction of the photoexcited ruthenium(II) complex ion ([Ru(bpy)3]2+*) by S2O82− ion. The mechanism of the reaction is presented to account for the results obtained.
The Synthesis of CdTe by Means of Fused Salt Electrolysis and Its Characterization
Authors: Minoura Hideki , Kitakata Masakazu , Sugiura Takashi , Murayama Minoru , Ueno Yasusada 
Published: July 2006

Abstract
Crystalline cadmium telluride layers of a cubic structure have been deposited potentiostatically on graphite cathodes by means of fused salt electrolysis employing CdCl2 and TeO2/Na2TeO3 in an LiCl–KCl eutectic melt at 450 °C. X-Ray diffraction and scanning-electron-microscope studies show that (i) these layers have a tendency to grow with a preferred orientation along the 〈111〉 direction and (ii) the surface morphology changes drastically with the change in the applied potential. Voltammetric analyses indicate two distinct mechanisms for cadmium telluride deposition; one is the codeposition of cadmium and tellurium occurring at potentials more negative than −0.2 V(vs. Ag/AgCl), and the other is the ionic reaction of the cathodically formed telluride ion with the cadmium ion occurring at potentials more negative than −0.7 V(vs. Ag/AgCl). As-deposited crystals are either n- or p-type, depending on the melt composition and the applied potential.
Application of Mössbauer Spectroscopy to a Structural Study of Superionic Conducting AgI–Ag2O–B2O3 Glasses
Authors: Nishida Tetsuaki , Ogata Michiko , Takashima Yoshimasa 
Published: July 2006

Abstract
A structural study of silver borate glasses containing 20 mol% AgI and 1 mol% 57Fe2O3 has been performed by Mössbauer spectroscopy. A Mössbauer spectrum of these glasses consists of an asymmetric quadrupole doublet with an isomer shift smaller than 0.4 mm s−1 with respect to metallic iron. This indicates that the individual Fe3+ ions are present at the substitutional sites of the tetrahedral boron atoms constituting BO4 units as a network former. An increase in the Ag2O content results in continuous decreases in the isomer shift and the quadrupole splitting when the Ag2O content exceeds about 16 mol%, which corresponds to the Ag2O/B2O3 ratio of 0.25 and the alkali oxide content of 20 mol% in the binary borate glasses. These results are ascribed to the formation of nonbridging oxygen atoms in the tetrahedral BO4 and FeO4 units. A glass transition temperature (Tg) of the glasses shows a distinct composition dependency, having a maximum around 16 mol% Ag2O. These lead to the conclusions that planar BO3 units are changed into the tetrahedral BO4 units in the lower Ag2O content region and that the nonbridging oxygen atoms are formed in the BO4 and FeO4 units when the Ag2O content is higher than 16 mol%. These conclusions are well consistent with the composition dependency of the electric conductivity which shows a minimum when the Ag2O content is 10–15 mol%.
Peptide Synthesis in Aqueous Solution. I. Application of p-Dialkylsulfoniophenols as a Water-Soluble Coupling Reagent
Authors: Kouge Katsushige , Koizumi Tatsuya , Okai Hideo , Kato Tetsuo 
Published: July 2006

Abstract
(p-Hydroxyphenyl)dimethylsulfonium methyl sulfate(HODMSP·MeSO4−) was found to be an excellent coupling reagent having a water-soluble property and a high reactivity; it worked as satisfactory as usual active esters in regard to the reactivity, product purity, and racemization. The marked advantage of the HODMSP·MeSO4− active ester method was the fact that bifunctional residues such as Arg, Lys, Cys, and Tyr could be selectively acylated when the pH of the reaction mixture was controlled. The molluscan neuropeptide FMRFamide(Phe–Met–Arg–Phe–NH2) was synthesized by this new active ester method for an evaluation of this method to further applications involving peptide syntheses.
Methanol-Incorporated Photoaddition of N-Methyl-1,2-naphthalenedicarboximide with Alkenes and Dienes
Authors: Kubo Yasuo , Mihara Mariko , Araki Takeo 
Published: July 2006

Abstract
Irradiation of acetonitrile-methanol solutions of N-methyl-1,2-naphthalenedicarboximide (1b) with 1,1-diphenylethylene gave a methanol-incorporated adduct at a carbonyl carbon atom in 1b together with 2,2-diphenylethyl methyl ether as a typical electron-transfer photosensitized product. The photoreaction of 1b with α-methylstyrene, styrene (2c), or 2-methyl-2-butene in the same solvent system gave a regio-isomeric pair of a mixture of two diastereomers of methanol-incorporated adducts at carbonyl carbon atoms. The irradiation of 1b with 2,3-dimethyl-2-butene and ethyl vinyl ether (2h) in benzene–methanol afforded methanol-incorporated adducts, although no reaction was observed for irradiation in acetonitrile–methanol. The irradiation of 1b with 2,5-dimethyl-2,4-hexadiene in acetonitrile–methanol also resulted in the formation of methanol-incorporated adducts. The values of the free-energy change associated with an electron-transfer (ΔGet) from the alkenes to the singlet excited state of 1b and fluorescence quenching rate constants support the photochemical single-electron-transfer mechanism for the addition. A preferential addition at the carbonyl carbon atom in 1b as well as that at the more sterically hindered carbonyl carbon atom in the reaction of 1b with 2c and 2h is explainable on the basis of the spin densities of the radical anion of 1b derived by a photochemical single-electron-transfer.