bluuebunny/crossref_metadata_2025_split huggingface dataset:
Usefulness of Some Plant Flowers as Natural Acid‐Base Indicators
Authors: Soltan M. E. , Sirry S. M. 
Published: May 2015

AbstractEnvironmental protection must require the use of natural products instead of chemicals to minimize pollution. Thus, this investigation studies the use of some plant flowers as naturally occurring acid‐base indicators. We utilized plant flowers of Celosiacristate Linn, Bombax ceiba L., Poincianaregia and Hibiscus subdariffa. These flowers contain anthocyanine pigments whose colour depends on pH; there fore they are used as pH indicators. The acid‐base equilibria of these pigments were investigated using spectro photometric and potentiometric methods. The pk values are 9.6 for Celosiacristate Linn, 5.7 for Bombax ceiba L., 8.6 for Poincianaregia and 2.8 & 7.3 for Hibiscus subdariffa. Experimentation of these indicators on different concentrations of acid‐base titrations in the presence of variable concentrations exhibited similar results as for synthetic indicators.
Synthesis and Antimicrobial Activity of Novel Furothienoquinoxalines, Pyranothienoquinoxalines and Pyrimidopyranothienoquinoxalines
Authors: Moustafa Osama S. , El‐Ossaily Yasser A. 
Published: May 2015

AbstractThe reaction of ethyl‐3‐mercaptoquinoxaline‐2‐carboxylate with phenacyl bromide, ethyl chloroacetate, chloroacetonitrile or chloroacetone furnished the corresponding 3‐hydroxy thieno[2,3‐b]quinoxaline. 2‐Cyano‐3‐hydroxythieno[2,3‐b]quinoxaline and 2‐acetyl‐3‐hydroxythieno[2,3‐b]quinoxa line were employed as precursors in the synthesis of some novel furo[2′,3′:4,5]thieno[2,3‐b]quinoxaline, pyrano[2′,3′:4,5]thieno[2,3‐b]quinoxaline and other heterocyclic systems fused with thieno[2,3‐b]quinoxalines. The antibacterial and antifungal activities of some the synthesised compounds were studied.
Synthesis and Antimicrobial Activity of New Pyridothienopyrimidines and Pyridothienotriazines
Authors: Abdel‐Rahman Abdu E. , Bakhite Etify A. , Al‐Taifi Elham A. 
Published: May 2015

Abstract5‐Acetyl‐3‐amino‐4‐aryl‐6‐methylthieno[2,3‐b]pyridine‐2‐carboxamides (5a,b) were reacted with triethyl orthoformate or nitrous acid to give the corresponding pyrimidinones6a,b and triazinones 7a,b. The reaction of 5a,b with acetic anhydride was carried out and its products were identified as a mixture of 8‐acetyl‐9‐aryl‐2,7‐dimethylpyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidine‐4(3H)‐one (9a,b) and related 5‐acetyl‐4‐aryl‐3‐biacetylamino‐6‐methylthieno[2,3‐b]pyridine‐2‐carbonitrile (10a,b). Reaction of 7a with some halocompounds afforded the N‐alkylated triazinones8a‐c. Chlorination of6a,b and 9a,b with phosphorus oxychloride produced 4‐chloropyrimidines 11a‐d which were used as precursors for the rest of the target heterocycles. Some of the prepared compounds were tested in vitro for their antimicrobial activities.
Studies on the Constituents from the Bark of Bauhinia Purpurea
Authors: Kuo Yueh‐Hsiung , Chu Pei‐Hung 
Published: May 2015

AbstractIn a previous paper, were ported a new stigmasteroyl glucoside derivative together with four known compounds. In addition to the above compounds, the isolation and identification of twenty‐four compounds from the same source are described here. Their structures were deter mined on the basis of spectral evidence as well as comparison with authentic samples. Those compounds included four waxes, four triterpenes, eight steroids, two glyceride, three flavonoids, and three phenylpropanoids. Some new compounds were found in mixtures of three alkyl ω‐hydroxyalkanoate, glyceride, and phenylpropanoids.
Temperature Dependent Dielectric Relaxation in Solvent Mixtures at Microwave Frequencies
Authors: Chaudhari Ajay , Chaudhari Harish , Mehrotra Suresh 
Published: May 2015

AbstractBy the use of time domain reflectometry method, dielectric measurements were carried out on dimethylformamide‐2‐nitrotoluene solvent mixtures in the frequency range 10 MHz‐20 GHz, at various temperatures from 15 °C to 45 °C. These solvent mixtures as well as pure solvents display a Debye type dispersion. Their frequency dependent dielectric properties can be summarized by the three parameters in the Debye equation: a static permittivity, permittivity at high frequency and a dielectric relaxation time constant. The free energy of activation for dipolar relaxation process and the Kirkwood correlation factor were determined using these fitting parameters for these solvent mixtures at various concentrations and temperatures. By using these dielectric parameters, the excess permittivity and excess inverse relaxation time is obtained. The excess permittivity is found to be positive for all concentrations and temperatures whereas the excess inverse relaxation time is negative.
Low‐Valent Ruthenium Induced Simultaneous Reduction of Nitro Group and C‐C Double Bond in Nitroolefin 1‐Phenyl‐2‐Nitropropene‐1
Authors: Li Yanjun , Izumi Taeko 
Published: May 2015

AbstractThe reduction of 1‐phenyl‐2‐nitropropene‐1 (1) on using ruthenium complexes was studied in detail in order to correlate this method with those previously recorded in the literature for the hydrogenation of nitroolefins. A variety of products was isolated by varying the reaction temperature and solvent. Among them was 1‐phenyl‐2‐propylamine (4), completely reduced from the selective both double bond and nitro group. 1‐Phenyl‐2‐propanol (5) was observed due to reduction of phenylacetone at 125 °C in the presence of ruthenium catalyst. When reaction temperature was lower than 125 °C, by employing RuCl2(PPh3)3 complex, 1‐phenyl‐2‐nitropropane (2) and phenylacetone (3) were obtained, respectively. Ru‐BINAP complexes were attempted to produce chiral amine from starting material 1‐phenyl‐2‐nitropropene‐1 (1).
Citric Acid Determination by Dual Wavelength Spectrophotometry
Authors: Farajzadeh Mir Ali , Nagizadeh Sepideh 
Published: May 2015

AbstractIn this study, a dual wavelength spectrophotometric method was presented on the basis of Cu2+‐NH3complex decomposition by the citrate ion and the formation of Cu2+‐citrate complex. Sum of the absorbance decreasing at 600 nm (λmaxfor Cu2+‐NH3complex) and the absorbance increasing at 750 nm (λmaxfor Cu2+‐citrate complex) was used in quantification. This method is very selective, fast and inexpensive but relatively less sensitive. The calibration curve is linear in the range of 0.4–8 mmol/L with a detection limit of 0.13 mmol/L. The relative standard deviation (RSD%) for the six repeated determinations (2 mmol/L) is 1.75%. Interference studies of more than twenty common compounds, which are present in the studied samples, were carried out. Only oxalic and ascorbic acids are serious interferes and which interferences were eliminated by simple procedures. Finally, the proposed method was successfully applied in the determination of citric acid content in ORS powder and some fruit juices.
Density and Partial Molar Volumes of Binary Mixtures for the Dimethyl Ether of a Glycol + Ethanol from T = 288.15 K to T = 318.15 K
Authors: Ku Su‐Chen , Tu Chein‐Hsiun 
Published: May 2015

AbstractDensities of {xCH3(OCH2CH2)vOCH3 + (1 ‐x)C2H5OH} for v = 1 − 4 at T = (288.15, 298.15, 308.15, and 318.15) K have been measured over the entire mole‐fraction range. The measurements were made by means of a vibrating‐tube densimeter. From these densities, some derived quantities, such as partial molar volumes and partial excess molar volumes have been obtained. Values of the limiting partial molar volumes and thence of the limiting partial excess molar volumes of the components have been derived. The densities can be expressed in terms of fourth‐degree polynomials with respect to the mole fraction of the glycol. The temperature has no significant effect on the partial molar volumes of the glycols with v = 3 and 4 in ethanol. These volumetric properties are discussed in terms of molecular interactions between the glycol and ethanol.
Vibrational and Rotational Excitations of Diatomic Molecules by Chirped Laser Pulses
Authors: Martin Rebekah , Kim Jung‐Hoon , Liu Wing‐Ki , Yuan Jian‐Min 
Published: May 2015

AbstractAfter a review of the “bucket dynamics” which classically accounts for the efficiency of chirped laser pulse excitation of the vibrations of a diatomic molecule, quantum mechanical results for the dissociation of diatomic molecules by a chirped pulse followed by a second laser pulse are presented. It is demonstrated that by using a second fixed‐frequency laser, dissociation without ionization is possible which each laser by itself would not suffice to dissociate the molecules. By using a second chirped laser pulse, additional excitation and dissociation of the molecule is observed. Similar to vibrational excitation, rotational excitation of a diatomic molecule can be accomplished by using a circularly polarized chirped laser pulse. Results of our quantum mechanical calculations show that coherent control of the rotational motion of a diatomic molecule is achievable.
Density Functional Calculations on the Heats of Formation of Certain Aromatic Nitro Compounds
Authors: Chen P. C. , Chieh Y. C. 
Published: May 2015

AbstractIn order to select suitable isodesmic reactions, heats of formation at 298 K of seven aromatic nitro compounds were calculated by various density functional theories, together with different basis sets. The calculated heats of formation for nitrobenzene, 1,2‐dinitrobenzene, 1,3‐dinitrobenzene, 1,4‐dinitrobenzene, 1,3,5‐trinitrobenzene, 1,2,3‐trinitrobenzene, and 1,2,4‐trinitrobenzene by various DFT methods were averaged to be 14.84, 23.23, 12.84, 12.89, 14.71, 30.61, and 25.73 kcal/mol, respectively. These values are very close to the experimental or multivariable linear regression results.
Theory of the Stark Effect on Single Molecular Spectroscopy
Authors: Hayashi M. , Chiang C. H. , Liang K. K. , Shiu Y. J. , Chang C. H. , Wu D. Y. , Li F. Y. , Chang T.‐C. , Wild U. , Latychevskaia T. Y. , Lin S. H. 
Published: May 2015

AbstractIn this work, we study a mechanism of the Stark effect on single molecular spectroscopy using the perturbation method. In particular, mechanisms of the induced dipole moment of a molecule imbedded in polar and non‐polar host molecules are theoretically investigated by applying LCAO MO to a guest molecule. Ab initio calculations are performed to study how the distance between a guest and a host molecule affects the induced dipole and quadrapole moments. We have found that the induced dipole moment is very sensitive to short range configurations while the induced quadrapole moment can be affected by longer range configurations.
Zinc(II) and Ruthenium(II) Complexes of Novel Fluorene Substituted Terpyridine Ligands: Synthesis, Spectroscopy and Electrochemistry
Authors: Thomas K. R. Justin , Lin J. T. , Chang Chen‐Pin , Chuen Chang‐Hao , Cheng Chung‐Chin 
Published: May 2015

AbstractTerpyridine ligands substituted with fluorene, fluorenylethynylthiophene and fluorenylethynylbenzene were obtained by applying Kröhnke synthesis and Sonogashira coupling reactions. [ZnL2]2+ and [Ru(L)‐(tpy)]2+ complexes were obtained by standard methods and characterized by spectroscopic and electrochemical methods. Zinc complexes are bright luminophores emitting blue to yellow colors depending on the nature of the conjugation in the ligand, while the ruthenium complexes do not emit at room temperature. The high quantum yields and short lifetimes indicate that the emission in the zinc complexes is mainly ligand centered.
Kinetics of Acid‐Catalyzed Dissociation of Copper(II) N‐Alkyl‐Substituted Diamino Diamide Complexes
Authors: Chao Min‐Shiun , Huang Shih‐Liang 
Published: May 2015

AbstractThe dissociation kinetics of the copper(II) complexes of 4‐methyl‐4,7‐diazadecanediamide (4‐Me‐L‐2,2,2), 4,7‐dimethyl‐4,7‐diazadecanediamide (4,7‐N,N′‐Me2‐L‐2,2,2), 4‐ethyl‐4,7‐diazadecanediamide (4‐Et‐L‐2,2,2), and 4‐methyl‐4,8‐diazaundecanediamide (4‐Me‐L‐2,3,2) have been studied at 25.0 °C and μ = 4.0 M (NaClO4 + HClO4) by the stopped‐flow method. These reactions are specific‐acid catalyzed; however, the rate constants of these reactions do not depend on the concentrations of acetic, chloroacetic, and dichloroacetic acids. At pH values below 1.4, both the proton‐assisted and the direct protonation pathways make contributions to the rates. The ratios of the rate constant of dissociation by the direct protonation pathway to the rate constant by the proton‐assisted pathway for the complexes in aqueous solution were measured and discussed.
Stereoselectivity in the Diels‐Alder Cycloadditions of a Facially Dissymmetric Bicyclo[2.2.2]octadiene‐Grafted Maleic Anhydride with Exocyclic Butadienes. Unexpected Facial Selectivity in the Cycloaddition with 2,3,5,6‐tetramethylidenebicyclo[2.2.2]octene
Authors: Chou Teh‐Chang , Kuo Liang‐Hsuan , Liu Kun‐Fa 
Published: May 2015

AbstractThe Diels‐Alder cycloadditions of facially dissymmetric maleic anhydride 1 with facially nonequivalent exocyclic 1,3‐butadienes(dimethylidenebicyclo[2.2.2]octene 3 and 2,3,5,6‐tetramethylidenebicyclo[2.2.2]‐octene (4)) were investigated. In each cycloaddition, the reaction occurred via the course in which 1 added exclusively by its syn‐face (same face as the etheno‐bridge) onto either π‐face of the exocyclic 1,3‐butadiene systems to produce only two of the four possible stereoisomeric monocycloadducts (8a/8b and 9a/9b). In the Diels‐Alder cycloaddition of 1 with bis‐exocyclic butadiene 4, however, both monocycloadducts 9a and 9b underwent subsequent cycloaddition with distinctive facial selectivity to produce the Cs‐symmetric bis‐cyclohexanobarrelene 10a as only bis‐cycloadduct.
Interaction of Trypan Blue with Protein and Application
Authors: Gao Hong‐Wen , Zhao Jian‐Fu 
Published: May 2015

AbstractThe microphase adsorption ‐ spectral correction (MPASC) technique has been described and applied to the aggregation of trypan blue (TB) in proteins. The formation of the microelectrostatic field in protein causes the Langmuir monolayer aggregation of TB. The adsorption ratio of TB to bovine serum albumin (BSA), ovalbumin (OVA), hemoglobin (Hb) and human γ‐globulin (γ‐G) was determined to be 14.8, 8.4, 2.8 and 27.6, respectively, and the adsorption constant of the aggregates to be 7.17 × 105, 4.88 × 106, 4.85 × 106 and 2.99 × 106. The adsorption ratio of TB to proteins interestingly indicates almost no relation to the array sequence of amino acid residues. The interaction of TB with proteins is sensitive at pH 3.29, and the reaction was applied to the determination of protein trace with satisfactory results.
Application of the Generalized Kinetic Ising Model to the Kinetics of Protein Folding
Authors: Liang Kuo Kan , Hayashi Michitoshi , Shiu Ying Jen , Mo Yan , Shao Jiushu , Yan Yijing , Lin Sheng Hsien 
Published: May 2015

AbstractThe kinetic Ising model in the mean field approximation has been applied to study the equilibrium and kinetic behaviors of protein folding‐unfolding. Thermodynamics and kinetics of protein folding‐unfolding are related by an elementary process of folding ↔ unfolding of peptide bonds. As a demonstration, we analyze, using the presented theory, the equilibrium and kinetics properties of Leu94Val mutant of horse cyt. c (Biochemistry 35, 5538 (1996).) and several characteristic properties are deduced using our theoretical model.
Thermodynamic Study of Complexation Phenomena of Some Alkaline Earth Metal (II) Complexes in Propanol‐1‐Water Mixtures at Various Temperatures
Authors: Bakr Moustafa F. 
Published: May 2015

AbstractThe stability constants of Mg2+, Ca2+, Sr2+ and Ba2+ perchlorates with 2,4‐diamino‐3,5‐dicyanothiophene (DADCT) have been determined at 15, 25, 35, 45 and 55 °C in 10, 20 and 30% (w/w) propanol‐1‐water mixtures using the conductometric technique.The conductometric data were analysed using a model 1:1 stoichiometry by which the stability constants, Ks, and the limiting molar conductance were obtained. The plots of specific conductance versus the molar ratio [A]o/[Cn+]o suggest that the stoichiometry of metal ion complexes is of a 1:1 complex.The stability constants tend to decrease with the atomic number as well as the ionic radii in the order Mg > Ca > Sr > Ba in 10% > 20% > 30% (w/w) propanol‐1‐water solvents. This trend was found to agree exactly with the Irving‐Williams series for all the systems under investigation.The thermodynamic parameters, ΔGo, ΔHo and ΔSo, for the complexation processes of all the complexes were evaluated and their significances were discussed.
Formation of Organometallic Heterocycles by S‐alkylated and N‐alkylated Ruthenium Vinylidene Complexes
Authors: Chang Chao‐Wan , Lin Ying‐Chih 
Published: May 2015

AbstractTreatment of [Ru]C=CPh (1, [Ru] = (η5‐C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with PhN=C=S at room temperature affords the [2 + 2] cycloaddition product (2) which contains a four‐membered‐ring heterocycle. A series of cationic S‐alkylated ruthenium vinylidene complexes [Ru]=C=C(Ph)C(=NPh)SCH2R+ (3a, R = CONH2; 3b, R = CH=CH2; 3c, R = p‐C6H4CF3) and N‐alkylated ruthenium vinylidene complexes [Ru]=C=C(Ph)C(=S)N(Ph)CH2R+ (4b, R = CH=CH2; 4c, R = p‐C6H4CF3) are prepared from 2 with organic halides at room temperature with high yields. Deprotonation of 3a and 3c by n‐Bu4NOH in acetone induces novel cyclization reactions via C‐C bond formation and yields neutral five‐membered‐ring heterocyclic complexes (5a, R = CONH2; 5c, R = p‐C6H4CF3). In a similar manner, deprotonation of 4b and 4c by NaOMe in CH2Cl2 also induces another cyclization to yield the pyrrole‐2‐thione complexes (6b, R = CH=CH2; 6c, R = p‐C6H4CF3). At room temperature, 5c isomerizes to the 2‐aminothiophene complex (7c) in solution.
Impedance Description of the Effect of the Polar Potential on a Schiff Base Self‐Assembled Monolayer
Authors: Ding Keqiang , Wang Qingfei , Jia Zhenbin , Tong Ruting , Wang Xinkui , Shao Huibo 
Published: May 2015

AbstractIn this paper, the effect of polar potentials on Schiff base self‐assembled monolayers was mainly investigated by the Electrochemical Impedance Spectroscopy (EIS) method. Different polar potentials and polarizing times were applied to this newly created monolayer, with an intention to reveal the relationship between the polar potential and the structure of this monolayer. The result showed that different polar potentials correspond to different complex resistance (Nyquist) plots, and the effect of polarizing time on this monolayer is regular and could be detected and reflected by the EIS plots conveniently. The results also demonstrated that the content of a C=N group related with the packing degree of this monolayer intimately, and the lower content of a C=N group corresponds to a denser structure of the monolayer, which could be presented by the value of electron transfer resistance (Rct). The main meaning of our work is to have developed one novel way that could reflect the relationship between the structure of the monolayer and the polar potential, which surely will encourage further experiments not only on Schiff bases but on other self‐assembled monolayer containing active groups.
A Preliminary Study on the Synthesis of Nano‐Sized Quartz
Authors: Li Li‐Jun , Fang Jiann‐Neng , Lo Huann‐Jih , Song Sheng‐Rong , Chen Yaw‐Lin , Chen Huei‐Fen , Lin I‐Chieh 
Published: May 2015

AbstractSilica gel was used as the starting material to synthesize nano‐sized quartz in the presence of alkaline solution. The experiments were carried out in autoclaves under the conditions of 0.25 M NaOH solution, 210 °C, and vapor pressure.SiO2‐X2 and α‐cristobalite appear as the intermediate unstable phases during the synthesis of quartz which occurs as a single stable phase in the synthetic product after 26 hour experiments. The growth of quartz can be separated into a fast linear growth with the rate of 75.3 nm/hr and a slow one with the rate of 1.4 nm/hr. It is shown that quartz begins to grow at 16.1 hours and the fast growth changes abruptly to the slow one at about 26.7 hours after the start of the experiments. On the other hand, nucleation occurs from 20 to 28 hours.For the synthetic quartz, an amount of about 32% of the population is nano‐sized, but most of the population (about 78%) lies between 50 nm and 300 nm, and the geometric mean size is about 182 nm.From the results of this preliminary study, it is encouraging that a high percentage of nano‐sized quartz could possibly be produced if suitable experimental conditions are chosen.
Separation of Herbicides from Aqueous Solutions by Paper Adsorption
Authors: Wang Wan‐Kung 
Published: May 2015

AbstractSeparation of the herbicides 2,4‐D methyl ester and pentachlorophenol from aqueous solutions by paper capillary permeation adsorption method was studied using paper. Nearly 43% and 99% of the investigated herbicides 2,4‐D methyl ester and pentachlorophenol, respectively, could be separated under optimum conditions. The effect of pH on the separation efficiency was studied in particular. At pH1–11 and 1, the maximum separation was achieved for 2,4‐D methyl ester and pentachlorophenol, respectively. The effects of herbicide concentration and some salts on the separatability were examined. Desorption techniques by elution with water to remove the herbicides from paper were developed. Moreover, the selective separation of the herbicides from the dispersion dyes methylene blue and congo red was attempted.
A Molecular Dynamics Simulation Study on Ion‐Conducting Polymer sPBI‐PS(Li+)
Authors: Yang Hsiao‐Ching , Huang Qiang , Hua Chih‐Yu , Lan Yi‐Kang , Chen Cheng‐Lung 
Published: May 2015

AbstractTo understand the mechanism of ionic migration in the amorphous matrixes of polymer electrolytes is crucial for their applications in modern technologies. Here, molecular dynamics (MD) simulation was carried out to investigate the ionic conduction mechanism of a particular conjugated rigid‐rod polymer, sPBI‐PS(Li+). The backbone of this polymer is poly[(1,7‐dihydrobenzo[1,2‐d:4,5‐d']diimidazole‐2,6‐diyl)‐2‐(2‐sulfo)‐p‐phenylene]. The polymer has pendants of propane sulfonate Li+ ionomer. The MD simulations showed that the main chains of sPBI‐PS(Li+) are in a layer‐like structure. The further detailed structure analysis suggested that the π‐electron of this polymer is not delocalized among aromatic rings. This agrees with the experimental result that sPBI‐PS(Li+) shows no electronic conductivity, and the conductivity of this polymer is mainly ionic. The calculated migration channels of lithium ions and electrostatic potential distributions indicated clearly that the polymer matrix is anisotropic for the migrations of ions. The migration of lithium ions along the longitudinal direction is more preferable than that along the transverse direction. The relaxations of the polymer host were found to play important roles in the transfer process of lithium ions. The hopping of lithium ions from one ‐SO3−1 group to another correlated strongly with characteristic motions of ‐SO3−1 group on a time scale of about 10−13 s.
A Theoretical Study of Face Selectivity in the Michael Addition of a Grignard Reagent with 5‐Substituted‐2‐dicyanomethyleneadamantanes
Authors: Wu Pei‐Fang , Wang I‐Ting , Lu Hsiu‐Feng , Yao Ching‐Fa , Sun Ying‐Chieh 
Published: May 2015

AbstractFace selectivity for the reactions of 5‐substituted (X)‐2‐dicyanomethyleneadamantanes with a Grignard reagent was examined using ab initio calculation for the substituents (X=F, Cl, Br, OH, NH2, and CH3). The calculated syn/anti product ratio based on the results of transition state energies for the halide substituents are in good agreement with the available experimental results. In addition, the results of the natural bond orbital calculation suggest that the through‐bond Cieplak hyperconjugation effect, instead of the through‐space interaction suggested by the experimental results in a prior study, is the main factor in determining face selectivity for the halide substituents in the present study, while for (X=OH, NH2, and CH3) substituents, other interactions may have unnegligible effects as well.