bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Stability of Bis(8-quinolinolato)copper(II)
Authors: Akaiwa Hideo , Kawamoto Hiroshi 
Published: July 2006

Abstract
The IR spectra of the titled and related compounds have been measured, and the stabilities of the chelates characterized by the relative strengths of the metalnitrogen bonds. An explanation has been made by comparing the extraction behavior of Cu(II) and Fe(III) chelates.
Synthesis and Absorption Spectra of 1,4-Diazaanthraquinone Derivatives
Authors: Nakazumi Hiroyuki , Agawa Testuro , Kitao Teijiro 
Published: July 2006

Abstract
A new 5-amino-1,4-diazaanthraquinone and related compounds were prepared from 2,3-dichloro-1,4-naphthoquinone by two different methods. The transition energies and electron densities of 5-amino- 1,4-diazanthraquinone and 1-aminoanthraquinone were calculated by a variable β,γ-modification of the PPP method.
Reactions of 2-Tosyloxy- and 2-Chlorotropones with Hydrazine, Methylhydrazine, and Phenylhydrazine
Authors: Imafuku Kimiaki , Kamachi Katsuya , Matsuda Yasunori , Matsumura Hisashi 
Published: July 2006

Abstract
The reactions of 2-tosyloxytropones or 2-chlorotropones with hydrazine, methylhydrazine, and phenylhydrazine gave 2-hydrazinotropones, 2-(α-methylhydrazino)-tropones, and 2-(β-phenylhydrazino)tropones, respectively. All the reactions are normal substitution at C-2 position of the tropone ring. No ciné reaction was observed. The reactivity of hydrazines decreases in the order: NH2NH2&gt;CH3NHNH2&gt;&gt;PhNHNH2.
Halogenated Sesquiterpene Phenols and Ethers from the Red Alga Laurencia glandulifera Kützing
Authors: Suzuki Minoru , Kurosawa Etsuro 
Published: July 2006

Abstract
Several brominated sesquiterpene phenols and the related ethers were isolated from the red alga Laurencia glandulifera Kützing. The structures of these compounds were determined on the basis of spectroscopic evidence and chemical correlation.
Diels-Alder Reaction of 2-Substituted Tropones with Ethylene. HMO Level Aspect of the Regioselectivity
Authors: Uyehara Tadao , Kitahara Yoshio 
Published: July 2006

Abstract
2-Chloro-, 2-methoxy-, 2-phenyl-, and 2-methyltropones (2,4,6-cycloheptatrien-1-ones) and benzoate of tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one) reacted with ethylene affording Diels-Alder type 1,4-addition products, bicyclo[3.2.2]nona-3,6-dien-2-ones. The regioselectivities of the cycloaddition are quite random, while they are reproduced by the calculated interaction energies based on Salem’s PMO equation which includes the closed-shell repulsion term.
Preparation of a Rare Earth Ion Selective Electrode
Authors: Takasaka Yoshihiro , Suzuki Yasuo 
Published: July 2006

Abstract
A new rare earth-ion selective electrode with a cerium(IV) oxide membrane has been prepared. The electrode was selective for the trivalent rare earths with a slope as great as 58 mV. The electrode was less selective for bi- and quadrivalent cations.
Reaction of Thiobenzamides with Arylmagnesium Bromides
Authors: Karakasa Takayuki , Hanzawa Takashi , Motoki Shinichi 
Published: July 2006

Abstract
Reactions of thiobenzamide, p-methylthiobenzamide, p-methoxythiobenzamide, and p-chlorothiobenzamide with 4 equivalents of phenyl-, p-tolyl-, p-methoxyphenyl-, and p-chlorophenylmagnesium bromides gave the corresponding diphenylmethyleneamine and thiobenzophenone as 1,2-addition produsts in good yields.
17O Nuclear Magnetic Resonance Studies. V. 17O Shieldings of Some Substituted Anisoles
Authors: Katoh Morimatsu , Sugawara Tadashi , Kawada Yuzo , Iwamura Hiizu 
Published: July 2006

Abstract
Fourier transform 17O NMR spectra have been measured for a number of meta and para substituted anisoles in natural abundance at 10.8 MHz. The shielding of the methoxyl oxygen nucleus decreases as the electron-withdrawing substituents are introduced to the ring. A good linear correlation is obtained for a plot of the 17O shifts versus the Hammett σ− constants.
Circular Dichroism and Stereochemistry of Tetranuclear Cobalt(III) Complexes of Hexol Type. II. Hexakis(ethylenediamine)-hexa-μ-hydroxo-tetracobalt(III) Ion, [Co{(OH)2Co(en)2}3]6+
Authors: Kudo Tomikatsu , Shimura Yoichi 
Published: July 2006

Abstract
The theoretically possible eight optical isomers of hexakis(ethylenediamine)-hexa-μ-hydroxo-tetracobalt(III) ion, [Co{(OH)2Co(en)2}3]6+, were separated by column chromatography, absorption and circular dichroism spectra being measured in the visible and ultraviolet region in 0.01 mol dm−3 HCl and 0.15 mol dm−3 Na2SeO3 solutions. Absolute configurations were determined by means of circular dichroism spectra and the characterization of mononuclear cobalt(III) ions produced by decomposition of the tetranuclear isomers in an acid solution. The additivity of the two main circular dichroism contributions due to the chiral CoO6 and CoN4O2 chromophores is discussed, and the configurational chirality of CoO6 chromophore is expressed by summing up the contributions from three pairs of CoN4O2 chromophores as in the so-called ring-pairing method.
Kinetic Study for the Reaction of (Arylthio)trimethylstannane with Benzoyl Chloride Giving S-Aryl Thiobenzoate.
Authors: Kozuka Seizi , Naribayashi Ikuya 
Published: July 2006

Abstract
A kinetic study has been conducted on the reaction of (arylthio)trimethylstannane with benzoyl chloride giving chlorotrimethylstannane and S-aryl thiobenzoate. The reaction has been found to obey a second order kinetic equation. A mechanism involving bimolecular nucleophilic attack of the sulfur atom on the acyl carbon has been suggested for the reaction based on the substituent effects of arylthio and benzoyl moieties.
Reduction of Transition-metal Salts by N-Propyl-1,4-dihydronicotinamide
Authors: Okamoto Tadashi , Ohno Atsuyoshi , Oka Shinzaburo 
Published: July 2006

Abstract
It was found that N-propyl-1,4-dihydronicotinamide reduces bis(benzonitrile)dichloropalladium, palladium(II) acetate, and chlorides of rhodium(III), platinum(IV), and ruthenium(III) smoothly in organic solvents affording a facile method for the preparation of low valent catalysts in situ.
The 2:1 Adduct of Chloro[N-(2-dimethylaminoethyl)salicylideneaminato]copper(II) with Chlorides of Copper(II), Manganese(II), and Nickel(II)
Authors: Tokii Tadashi , Kaneko Makoto , Yamanaka Kusuo , Muto Yoneichiro , Kato Michinobu 
Published: July 2006

Abstract
The adducts listed in the title have been prepared, and their trimeric nature confirmed on the basis of elemental analysis and IR and electronic spectra. The magnetic properties of the MnCl2 and NiCl2 adducts have been analyzed in terms of a linear trimer model.
Reaction of Guaioxide with N-Bromosuccinimide and the Preparation of 4,6-Guaiadien-3-one and 1-Epi-4,6-guaiadien-3-one
Authors: Hirota Hiroshi , Moriyama Yoshihiko , Shirasaki Hidekazu , Tsuyuki Takahiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
Treatment of guaioxide with N-bromosuccinimide gave 4-bromoguaioxide, which was dehydrobrominated to yield 3-dehydroguaioxide. The olefin was then converted into 8-deoxytorilolone and 8-deoxy-1-epitorilolone by the known procedures. Dehydration of these deoxy derivatives in benzene in the presence of p-toluenesulfonic acid gave 4,6-guaiadien-3-one and 1-epi-4,6-guaiadien-3-one, respectively.
syn- and anti[3.3](1,4)Naphthalenophanes
Authors: Yoshinaga Minoru , Otsubo Tetsuo , Sakata Yoshiteru , Misumi Soichi 
Published: July 2006

Abstract
The title compounds were prepared by pyrolysis of disulfones. The absorption spectra depend rather on the stacking mode between two naphthalene rings than ring-to-ring distance, whereas for the emission spectra the reverse is the case. A [4+4]photocycloaddition and a reverse reaction were observed between anti-form and its photoisomer.
Reactions of Trimethylsilyl Cyanide and N-(Trimethylsilyl) diphenylmethyleneamine with Nitrones and Thermal Decompositions of Their Adducts
Authors: Tsuge Otohiko , Urano Satoshi , Iwasaki Takahiko 
Published: July 2006

Abstract
Trimethylsilyl cyanide (1) and N-(trimethylsilyl)diphenylmethyleneamine (2) reacted with α-aryl-N-phenyl-nitrones to afford the corresponding 1: 1 adducts 4 and 5 respectively. Thermal decomposition of 4 in refluxing xylene gave azoxybenzene, stereoisomers of 2,3-diarylsuccinonitriles, α-iminonitriles and/or benzanilides, whose yields depended on the nature of substituents on phenyl group of 4. On heating in benzene 5 afforded a mixture of azoxybenzene and meso-N,N′-bis(diphenylmethylene)-1,2-diarylethylenediamines. On the other hand, reactions of 1 and 2 with N-(diphenylmethylene)aniline N-oxide or N-(9-fluorenylidene)aniline N-oxide did not give the corresponding 1: 1 adducts, but instead compounds arising from thermal decomposition of initial 1: 1 adducts were directly obtained. The reaction of 1 with N-(p-diethylaminophenyl)-α-phenylnitrone leading to the corresponding α-imino nitrile is also described.
An Ultrasonic Method for Determination of the Difference in Hard-Sphere Volume of Conformational Isomers
Authors: Aoi Masakatsu , Arakawa Kiyoshi 
Published: July 2006

Abstract
An ultrasonic method for determining the difference in hard-sphere volume of conformational isomers from sound velocity has been worked out, its accuracy being improved by taking the temperature dependence of the effective hard-sphere diameter into account. The difference for 1,2-dibromoethane, 1,1,2-trichloroethane, methylcyclohexane, and 1,2-dichloroethane was determined. The fractions of volume differences ΔV⁄V in these liquids were found to be 4.5, 5, 11, and 19% for 1,2-dibromo-, 1,1,2-trichloroethane, methylcyclohexane, and 1,2-dichloroethane, respectively.
Polymerization of Silicic Acid Adsorbed on Iron(III) Hydroxide
Authors: Yokoyama Takushi , Nakazato Tatsuo , Tarutani Toshikazu 
Published: July 2006

Abstract
Adsorption of silicic acid on iron(III) hydroxide from aqueous solution and polymerization of adsorbed silicic acid were affected by pH, concentration of silicic acid before and after adsorption, or the relative amount of silicic acid and iron(III) hydroxide. The amount of adsorbed silicic acid and the rate of its polymerization were maximum at pH 9. The polymerization reaction of silicic acid on the surface of iron(III) hydroxide was found to consist of two steps: (1) polymerization of adsorbed monosilicic acid and (2) polymerization between monosilicic acid in the solution and silicic acid species already present on the surface of iron(III) hydroxide, giving a three-dimensional gel structure.
Quenching of Excited Zinc(3PJ) and Zinc(1P1) Atoms by Several Gases
Authors: Yamamoto Shunzo , Takei Takashi , Nishimura Norio , Hasegawa Shigeo 
Published: July 2006

Abstract
The intensities of the 307.6 nm and 213.9 nm resonance lines of zinc were measured at different pressures of several gases, and the quenching rate constants were determined on the basis of the Stern-Volmer plots. The quenching cross-sections obtained here were compared with those for mercury and cadmium. The simple chargetransfer curve-crossing theory proposed by Breckenridge and Renlund for the quenching of excited cadmium and mercury atoms by N2, CO, CO2, and so on was found to be useful for the quenching of excited zinc atoms, as well. Isotope effects on the quenching of Zn(3PJ) and Zn(1P1) by H2 and D2 were also discussed.
CHEMISTRY OF THIO-CHOLINE HALIDE (TRIMETHYL THIO-ETHYL AMMONIUM HALIDE). II NEW THIO-CHOLINE CHLORIDE AND ITS DERIVATIVES
Authors: Harada Taichi 
Published: July 2006

Abstract
1. Chloro-choline chloride was obtained by the condensation of trimethylamine with ethylene chloride. It decomposes slowly above 163°C. melting and boiling, at 242°C. with a reddish brown discoloration.
2. Thio-choline chloride was prepared from chloro-choline chloride by the action of 2-thio uracil at 150°C. Its isoelectric point was found to be at PH 7.0. It decomposes slowly above 200°C. (approximately), melting and boiling at 238°C.
3. Thio-choline chloride reacts with silver chloride to form (Remark: Graphics omitted.) whose solubility in water at 37° was found to be 0.1215 gr. It decomposes slowly above 70°C. (approximately), melting and boiling around 228°C.
Palladium-Catalyzed, Atmospheric Pressure Carbonylation of Allylic Halides under the Influence of Sodium Hydroxide or Alkoxides. A Facile Synthesis of β,γ-Unsaturated Acids
Authors: Okano Tamon , Okabe Nobuyuki , Kiji Jitsuo 
Published: July 2006

Abstract
The palladium-catalyzed, atmospheric-pressure carboxylation of allylic halides occurs readily in an aqueous sodium hydroxide/organic solvents two-phase system, giving β,γ-unsaturated acids. Phosphine complexes [PdCl2L2] (I, L = m-(Ph2P)C6H4SO3Na; II, L = Ph3P) or Na2[PdCl4] (III) can be used as the catalyst. Atmospheric-pressure alkoxycarbonylation is realized under the influence of a homogeneous alcoholic solution of sodium alkoxide. Phosphine-free palladium complexes, such as [(π-allyl)PdCl]2 or III, are the favored catalyst. β,γ-Unsaturated esters are obtained in high yields.
Syntheses of and Restricted Csp3–Csp2 Bond Rotation in Triptycenes That Carry C4-Olefinic Substituent at 9-Position
Authors: Oki Michinori , Taguchi Yasushi , Toyota Shinji 
Published: July 2006

Abstract
Triptycene derivatives that carry C4-olefinic substituents at the 9-position, in which the olefin is connected to C(9) through an sp2 carbon, are synthesized. Their dynamic behaviors, as observed by dynamic NMR technique, are discussed on the basis of the results of MM2 calculations. The barrier to rotation of the olefinic groups is higher when there is a methyl group which directs inside relative to the triptycene skeleton, than the cases where no such a methyl group exists.
Refolding of Trimeresurus flavoviridis Phospholipases A2
Authors: Tsuno Shinji , Ogawa Tomohisa , Nakashima Kin-ichi , Oda Naoko , Lee Sannumu , Shimohigashi Yasuyuki , Aoyagi Haruhiko , Ohno Motonori 
Published: July 2006

Abstract
Trimeresurus flavoviridis (Habu snake) venom contains phospholipase A2 (PLA2) isozymes which are rich in disulfide bond and show diverse activities in spite of their highly homologous structures. When reduced form of Tyr(NO2)-67-PLA2, which is a mimic of Asp-49-PLA2 mutant, was oxidized at pH 8.0 in the presence of 5 mM L-cysteine and 5 mM Ca2+, native form of Tyr(NO2)-67-PLA2 was produced as being judged from both activity regeneration and adequate HPLC profile. Reduced forms of two Lys-49-PLA2 isozymes with extremely low lipolytic activity, which are called basic proteins I and II, also generated native forms of proteins when oxidized under the same conditions as above. Protein disulfide isomerase accelerated proper folding of reduced Tyr(NO2)-67-PLA2 at an initial phase of oxidation and was effective for rearrangement of incorrectly paired disulfide bonds of Asp-49-PLA2 to native construction. However, this isomerase failed to convert reduced form of partially active L-fragment, Asp-49-PLA2 lacking N-terminal octapeptide, to the native form, indicating that the entire sequence of protein in a nascent state is primarily required for proper folding. The present data together with the fact that reduced Asp-49-PLA2 folded properly (S. Tanaka et al. J. Biochem., 96, 1443 (1984)) afforded a strong basis for the structure and function study of T. flavoviridis PLA2s by means of in vitro mutagenesis technique.
Synthesis of 2-(Substituted Methyl)-3,4-Disubstituted Pyrroles and Their Conversion into the Corresponding Porphyrins
Authors: Kinoshita Hideki , Tanaka Shingo , Nishimori Natsu , Dejima Hiroshi , Inomata Katsuhiko 
Published: July 2006

Abstract
2-Hydroxymethyl-1-methylsulfonyl-3,4-disubstituted pyrroles and 2-hydroxymethyl-3,4-disubstituted pyrroles were effectively converted into the corresponding 2-(substituted methyl)pyrrole derivatives by the reaction with various nucleophiles in the presence of base. These products were further transformed to the corresponding porphyrins regioselectively under almost neutral or basic conditions.
The Resolution and Absolute Configuration of 2,3-Methanopyroglutamic Acid, 3-Oxo-2-azabicyclo[3,1,0]hexane-1-carboxylic Acid
Authors: Kodama Hiroaki , Matsui Shinichi , Kondo Michio , Stammer Charles H 
Published: July 2006

Abstract
The resolution of racemic 2,3-methanopyroglutamic acid (∇Glp) was accomplished using L- and D-Leu-NH2 and both isomers were hydrolyzed to give optically active (Z)-2,3-methanoglutamic acids1) (∇ZGlu), respectively. The optical rotations of these samples were compared with ∇ZGlu obtained by hydrolysis of ∇Glp prepared by oxidation of (2S,3R)- or (2R,3S)-2,3-methanoproline1) (∇Pro), the absolute configurations of which were determined by X-ray diffraction earlier. These experiments showed (−)- and (+)-∇Glp to have the (2S,3S)- and (2R,3R)-configurations, respectively.
Enantioface Differentiating Reduction of Keto Acid in the Presence of 6-Deoxy-6-amino-β-cyclodextrin with NaBH4 in Aqueous Media
Authors: Hattori Kenjiro , Takahashi Keiko , Sakai Naoki 
Published: July 2006

Abstract
The formation of an inclusion compound and the interaction of both ionic and hydrogen bonding were shown to be indispensable in the asymmetric reduction of keto acid in the presence of 6-deoxy-6-amino-β-cyclodextrin with NaBH4 in an aqueous buffer solution. Furthermore, multiple interactions were elucidated and the enantioface differentiating reduction was induced in the concerted interactions. A mechanistic scheme for the enantioface differentiating attack of a reducing-reagent on the included substrate was suggested.
Lattice Parameters of Sol–Gel Derived Metastable ZrO2–CaO Solid Solutions
Authors: Yoshioka Hideki 
Published: July 2006

Abstract
Metastable cubic and tetragonal phases in (1−x)ZrO2–xCaO solid solutions (x = 0–0.155) were prepared by the sol–gel method. A sequential phase transition from amorphous to cubic, tetragonal, tetragonal+monoclinic with a rise in treatment temperature was observed for specimens of x = 0.044. The lattice parameter of the metastable cubic phases changed linearly with the composition, indicating that the Vegard’s law can be extended to the metastable phase. The validity of the Vegard’s law and the stability of metastable phases are discussed.
Highly Selective Membrane Transport of Zn2+ Ion by a Cooperative Carrier Composed of 1,10-Diaza-18-crown-6 and Palmitic Acid
Authors: Dadfarnia Shayessteh , Shamsipur Mojtaba 
Published: July 2006

Abstract
A mixture of 1,10-diaza-18-crown-6 and palmitic acid was found to be an excellent cooperative carrier for the uphill transport of Zn2+ ions through a chloroform liquid membrane. In the presence of histidine, as a suitable metal ion acceptor in the receiving phase, it can selectively and efficiently transport Zn2+ ion from aqueous solutions containing other cations such as Na+, K+, Mg2+, Ca2+, Mn2+, Cu2+, Ni2+, Co2+, Hg2+, Pb2+, and Cd2+. Amount of Zn2+ transport across the liquid membrane after 2 h is about 90%, while that of other cations is &lt; 4%.
Generation and Characterization of 1,3-Di-t-butyl- and 1,3-Di-t-butyl-4,6-dimethylthieno[3,4-c]thiophenes
Authors: Ishii Akihiko , Ida Yutaka , Nakayama Juzo , Hoshino Masamatsu 
Published: July 2006

Abstract
1,3-Di-t-butyl- and 1,3-di-t-butyl-4,6-dimethylthieno[3,4-c]thiophenes (1g and 1h) are generated by Pummerer dehydration of the corresponding sulfoxides (4 and 5, respectively) in boiling acetic anhydride and can be trapped with N-phenylmaleimide (NPM). Both endo- and exo-adducts are formed from 1g and NPM, while only exo-adduct is formed from 1h and NPM. Reduction and isomerization of the starting materials occur in the reactions of 4 and 5 with trifluoroacetic anhydride. The reaction of 5 with trifluoroacetic anhydride in the presence of 2,6-lutidine also gives 4,6-di-t-butyl-1-(trifluoroacetylmethylene)-3-methyl-1H,3H-thieno[3,4-c]thiophene.
Reactions of 1,2-Propadienyl Sulfides with Aldehydes and Acetals Catalyzed by BF3·OEt2
Authors: Narasaka Koichi , Shibata Takanori , Hayashi Yujiro 
Published: July 2006

Abstract
Ene reaction proceeds between 1-alkyl-1,2-propadienyl sulfides and aldehydes in the presence of BF3·OEt2 to afford 1,3-dienes possessing an alkylthio group. On the other hand, the reactions of 1-silyl-1,2-propadienyl sulfides with aldehydes or their dimethylacetals give aldol-type addition products, α-methylene acylsilanes.
Refinement of the Crystal Structure of Pentaerythritol Tetracetate
Authors: Uechi Tetsuo , Fuchita Yoshio 
Published: July 2006

Abstract
The crystal structure of the title compound has been refined to a final R value of 0.041 (weighted R = 0.032), with 380 reflection data measured on a four-circle X-ray diffractometer. The overall structural features show no significant differences from those in the original determimation, while the structural parameters have been improved in precision.
Partial Reduction of Dithioacetals with Phosphorus Reagents
Authors: Saimoto Hiroyuki , Kanzaki Atsuhiro , Miyazaki Kazumi , Sashiwa Hitoshi , Shigemasa Yoshihiro 
Published: July 2006

Abstract
Acyclic dithioacetals 1 derived from di- and monoaryl ketones were monodesulfurized with diphosphorus tetraiodide or dimethyl phosphonate. A side product 5 from the reaction of 9,9-bis(ethylthio)-9H-fluorene with phosphorus triiodide suggested the intermediacy of an anionic species.
A Convenient Preparation of 2,4,6-Trisubstituted 1,3,5-Triselenanes by Treating Aldehydes or Their Acetals with 2,2,4,4,6,6-Hexamethyl-1,3,5-triselena-2,4,6-tristannacyclohexane in the Presence of BF3·OEt2 and AlCl3
Authors: Shimada Kazuaki , Okuse Satoshi , Takikawa Yuji 
Published: July 2006

Abstract
A convenient preparation of 2,4,6-trisubstituted 1,3,5-triselenanes was achieved by the treatment of aldehydes or their acetals with 2,2,4,4,6,6-hexamethyl-1,3,5-triselena-2,4,6-tristannacyclohexane, (Me2SnSe)3, in the presence of BF3·OEt2 and AlCl3.
Studies on Aromatic Sesquiterpenes. XIII. Synthesis of Lacinilene A and Its Structural Isomer
Authors: Tanaka Juichi , Miyake Takashi , Iwasaki Noboru , Adachi Kazuo 
Published: July 2006

Abstract
Lacinilene A (6-norcadalen-7-ol) was synthesized from anisole through 6-norcalamenen-7-ol. 6-Nordaucalen-7-ol also synthesized.
Tetrakis(pyridine)silver(II) Peroxodisulfate, [Ag(py)4]S2O8, a Reagent for the Oxidative Transformations
Authors: Firouzabadi Habib , Salehi Peyman , Mohammadpour-Baltork Iraj 
Published: July 2006

Abstract
Tetrakis(pyridine)silver(II) peroxodisulfate oxidizes aromatic aldehydes to carboxylic acids, benzylic alcohols to carbonyl compounds, aromatic thiols, and allylaryl thioethers to arylsulfonic acids and benzylic carbon–hydrogen bonds to carbonyl groups. α-Hydroxycarboxylic acids and phenylacetic acids are decarboxylated to produce carbonyl compounds. Dibenzyl ether and its sulfur analogue are converted to their corresponding ester and the thioester, respectively.
2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline as an Analytical Reagent for the Spectrophotometric Determination of Microamount of Gold(III)
Authors: Amin Alaa S , Shakra S , Abdalla A A 
Published: July 2006

Abstract
The synthesis, spectral characteristics, and analytical application of 2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) are described. A simple, rapid, selective, and sensitive spectrophotometric method for the determination of microgram amounts of gold, alone, or in the presence of associated metals, is developed, based on the color reaction between the metal ion and the reagent. The yellowish brown complex (λmax = 575 nm) has stoichiometric ratio (1 : 1) [metal : ligand] over the pH range 3.4 to 7.0. Beer’s law is obeyed over the concentration range 0.1—6.9 μg cm−3 of gold. The molar absorptivity and Sandell’s sensitivity of the method are 1.52 × 104 dm3 mol−1 cm−1 and 0.016 μg Au cm−1 respectively. The relative standard deviation for six replicate determination of 2.95 μg cm−3 of gold(III) is 1.37%. The interference of various ions has been studied and conditions were developed for the determination of gold in alloys and some synthetic samples without the need for extraction or heating.