bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Bonding in Hydrogen Molecular Ion and Competition between Laser‐induced Ionization and Dissociation
Authors: Yuan Jian‐Min , Duan Yiwu , Liu Wing‐Ki 
Published: May 2015

AbstractJust as a helium atom is a prototype for atoms, a hydrogen molecular ion is a prototype for chemical bonding in molecules. In the presence of an external field, the latter also serves as a prototype for which field‐induced ionization and dissociation compete with each other. Pauli was the first to examine the nature of chemical bonding in terms of the old quantum theory. In view of the recent developments of nonlinear dynamics and quantum chaos, we re‐examine the negative conclusion that he reached in his thesis. In particular, we are interested in finding out whether the classical three‐body system is stable and whether any part of the chemical bonding can be attributed to its classical stability. Our result shows that indeed classical phase space structures exist which contribute to chemical bonding, when quantized semiclassically. Thus chemical bonding is not a purely quantum phenomenon, as generally believed.We also examine the classical dynamical behavior of this three‐body system in the presence of an external field beyond the Born‐Oppenheimer approximation. Interesting competition exists between ionization, dissociation, and Coulomb explosion. Although ionization dominates over dissociation at high laser fields, there exists a range of laser intensity below 150 TW/cm2 for which we can concentrate on dissociation alone without significant interference from the ionization process.
Preferential Oxygen‐Trapping in Metallic Multilayers: ASIMS Perspective
Authors: Sarkar Subhendu , Chakraborty Purushottam 
Published: May 2015

AbstractThe matrix effect in a secondary ion mass spectrometry (SIMS) depth profile can distinctly represent any change in the chemistry of surface or interface regions of thin films or multi layered structures. Present work shows how a preferential in corporation of oxygen in metallic multi layered structures has been manifested by such an analysis.
Independence of the Second‐Order Perturbed Total Energy on the Screening Charge
Authors: Cheng Wen‐Yu , Huang Keh‐Ning 
Published: May 2015

AbstractThe non‐relativistic total energy of a many‐electron atomic system up to the second order in the perturbation theory is proved to be in dependent of the choice of the screening charge in the unperturbed Hamiltonian with a central Coulombic potential. The ground‐state energy of a helium‐like ion is calculated as a demonstration.
The Host/Guest Type of Excited‐State Proton Transfer; a General Review
Authors: Chou Pi‐Tai 
Published: May 2015

AbstractContemporary progress regarding guest/host types of excited‐state double proton transfer has been reviewed, among which are the biprotonic transfer within doubly H‐bonded host/guest complexes, the transfer through a solvent bridge relay, the intramolecular double proton transfer and solvation dynamics coupled proton transfer. Of particular emphases are the photophysical and photochemical properties of excited‐state double proton transfer (ESDPT) in 7‐azaindole and its corresponding analogues. From the chemical aspect, two types of ESDPT reaction, namely the catalytic and non‐catalytic types of ESDPT, have been classified and reviewed separately. For the case of static host/guest hydrogen‐bonded complexes both hydrogen‐bonding strength and configuration (i.e. geometry) play key roles in accounting for the reaction dynamics. In addition to the dynamical concern, excited‐state thermodynamics are of importance to fine‐tune the proton transfer reaction in the non‐catalytic host/guest type of ESDPT. The mechanisms of protic solvent assisted ESDPT, depending on host molecules and proton‐transfer models, have been reviewed where the plausible resolution is deduced. Particular attention has been given to the excited‐state proton transfer dynamics in pure water, aiming at its future perspective in biological applications. Finally, the differentiation in mechanism between solvent diffusive reorganization and solvent relaxation to affect the host/guest ESPT dynamics is made and discussed in de tail.
Complexation Kinetics of N‐Alkyl‐Substituted Diamino Diamides with Nickel (II) in Aqueous Solution
Authors: Chao Min‐Shiun , Huang Shih‐Liang 
Published: May 2015

AbstractEquilibrium constants are deter mined for the protonation and metal complexation of the nickel(II) complexes with 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‐ diazaundecane diamide (4‐Me‐L‐2,3,2), in 0.10 M KCl at 25.0°C. The formation kinetics of these nickel (II) complexes have been studied under the same conditions with use of the stopped‐flow technique. The possible path ways for the complexation reaction of nickel (II) with these ligands are discussed. The first metal‐nitrogen bond formation is proposed as the rate‐determining step for the reactions of nickel (II) with the unprotonated ligands; proton loss is the rate‐limiting step in the reactions of nickel (II) with the monoprotonated ligands. Similarly, in dissociation reactions of these nickel (II) complexes, the rate‐determining step for the water dissociation pathway is the break age of the second nickel‐nitrogen bond; the rate‐determining step for the proton‐assisted path way is the protonation of the released amino group. The important factors determining the reactivity of these complexes are considered. The kinetic results of the formation and dissociation reactions of these complexes are consistent with dissociative mechanism.
The HPLC Resolution of Nucleic‐Acid Bases and An a Log Hypoxanthine on R,S‐2‐Hydroxypropyl Derivatized β‐Cyclodextrin Bonded Chiral Stationary Phase Using a Water‐Based Mobile Phase
Authors: Chen Shushi 
Published: May 2015

AbstractA HPLC approach using R,S‐2‐hydroxypropyl derivatized β‐cyclodextrin packed column as the stationary phase was developed to resolve five nucleic‐acid bases and an a log hypoxanthine in the reversed‐phase mode. These bases are not only similar in structure but also very close in basicity. However, the resolution can be completed in less than ten minutes and is considered to be better carried out on the R,S‐2‐hydroxypropyl derivatized β‐cyclodextrin phase than that obtained on the native β‐cyclodextrin phase under the same chromatographic conditions. The mechanism involved in the resolution is believed to be inclusion complexation between the analyte and the cavity of cyclodextrin in the reversed‐phase mode. The retention time was found relevant to the size of the analyte. The number of groups on analyte that is available to form hydrogen bonding with hydroxyl groups on CDs also affects the retention scale. Factors of introducing organic acid and base or organic modifier such as methanol to the water‐based mobile phase or increasing their percent ages in the mobile phase decreases the retention time without de grading the resolution significantly.
The Syntheses of 4‐Arylamino‐1,2,3‐Triazoles and Stable 6‐Sydnonyl Verdazyls from Sydnone Derivatives and Their Fragments
Authors: Kuo Wen‐Fa , Lin I‐Tzu , Sun Shiaw‐Wen , Yeh Mou‐Yung 
Published: May 2015

Abstractα‐Chloroformylarylhydrazones 1 and α‐chloroformylarylhydrazones of sydnonecarbaldehydes 3 have been prepared by a new synthetic route: α‐chloroformylarylhydrazines hydrochlorides 2 reacted with corresponding carbonyl compounds. Reactions of compounds 3 with various hydrazines to give 6‐sydnonyl‐1,2,4,5‐tetrazinan‐3‐ones 7 and/or carbazones 8 were also investigated. By oxidization with lead dioxide, compounds 7 were trans formed to stable 6‐sydnonyl‐3,4‐dihydro‐3‐oxo‐1,2,4,5‐tetrazin‐1(2H)‐yl radical derivatives 9 (sydnonyl verdazyls). Furthermore, sydnonecarbaldehydes arylhydrazones 5 through acidic conditions could be transferred to 4‐arylamino‐1,2,3‐triazoles 6 which were also obtained by means of acidic decompositions of 4‐formylsydnones 10.
The Synthesis of Some New 7‐Methyl‐3‐substituted‐1,2,4‐triazolo[3,4‐b]benzothiazoles
Authors: Dong Heng‐Shan , Zhang Ji‐Yong , Tang Yan‐Bo , Mao Xue‐Rong , Quan Bin 
Published: May 2015

AbstractNew 7‐Methyl‐3‐substituted‐1,2,4‐triazolo[3,4‐b]benzothiazoles were synthesized from p‐methylaniline to 5 with various aromatic carbonic acids. The yielded product 6a‐j was investigated with Elemental analyses, NMR, MS and IR techniques.
Syntheses of 5‐Hexadecanolide, 6‐Acetoxy‐5‐hexadecanolide and Tanikolide
Authors: Chang Meng‐Yang , Lin Chien‐Lun , Chen Shui‐Tein 
Published: May 2015

AbstractTotal syntheses of 5‐hexadecanolide (1), 6‐acetoxy‐5‐hexadecanolide (2) and tanikolide (3) are described. 1‐Bromoundecane (4) and 5‐benzyl‐1‐pentanal (5) were chosen as starting materials. Wittig olefination and Grignard addition 4 and 5 afforded the 16‐carbon skeleton, which under went a series of functional group transformations to give δ‐lactonederivatives 1, 2 and 3.
Preparations of Tris(Triphenylphospnine)copper and Tris(triphenylphosphine)silver Complexes of Phenalenone, Diphenylcyclopropenone and Tropone
Authors: Chen Yen‐Hsien , Lin Ching‐Cheng , Lin See 
Published: May 2015

AbstractThe tris(triphenylphosphine)copper and tris(triphenylphosphine)silver complexes of phenalenone 4, diphenylcyclopropenone 5 and tropone 6 were prepared by treating tris(triphenylphosphine)copper tetrafloroborate 2 and tris(triphenylphosphine)silver tetrafluoroborate 3 with basic ketones 4, 5 and 6 in high yields. All these complexes are stable in either air or moisture, and soluble in common organic solvents such as dichloromethane and chloroform.
Corrosion Behavior of Aluminum in Non‐Uniform Electric Fields
Authors: Dobrewsky Ivan , Sabeva Emilia , Petkova Nedialka 
Published: May 2015

AbstractThe present paper discusses the effect of the geometrical structure of the electric fieldon the corrosion of aluminum cathodes by electrolysis of aqueous solutions of sodium chloride. A correlation between the mass of the aluminum dissolved from the cathode and the factors electric current density, distance between the electrodes, electrolysis time and sodium chloride concentration by electrolysis with direct current in electric fields of various geometries was found.
Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams
Authors: Wang Eng‐Chi , Huang Keng‐Shiang , Lin Kuo‐Fan , Chen Jan‐Cheng 
Published: May 2015

AbstractThe mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M+‐29], [M+‐55], and [M+‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.
Synthesis of Elvirol Methyl Ether
Authors: Ho Tse‐Lok , Ho Meng‐Fen 
Published: May 2015

AbstractElvirol methyl ether has been synthesized from p‐cresol via 2‐(2‐cyclopentenyl)‐4‐methylphenyl methyl ether by ozonolysis, dithioacetalization, reduction, and Wittig reaction. The over all yield was 18.8%.
Synthesis of Iridoid Monoterpenes and Prostaglandins, via Photochemical Rearrangement of Bicyclo[2.2.1]hept‐5‐en‐2‐One
Authors: Tai Huo‐Mu , Yang Chau‐Chen , Yeh Min‐Ling , Chang Nein‐Chen 
Published: May 2015

AbstractThe synthesis of cyclopentanoid natural products, iridoid monoterpenes and prostaglandins, was achieved from a common intermediate 2, which was obtained from 1 via photochemical rearrangement.
Synthesis of the Chiral Pair of a Novel Thromboxane Antagonist, 3‐[2‐(3‐Benzenesulfonylamino‐7‐oxabicyclo[2.2.1]hept‐2‐yl‐methyl)phenyl] Propionic Acid
Authors: Chern Ching‐Yuh , Yek Yung Lee , Jan Ja‐Ding , Kan Wai Ming 
Published: May 2015

AbstractPreparation of the enantiomeric pair of 3‐[2‐(3‐benzenesulfonylamino‐7‐oxabicyclo[2.2.1]hept‐2‐yl‐methyl)phenyl] propionic acid, a novel thromboxane antagonist is reported. They are synthesized from either enantiomers of known (1R,2R,3R,4S)‐3‐[2‐(3‐carboxy‐7‐oxabicyclo[2,2,1]hept‐2‐yl‐methyl)phenyl]‐propionic acid methyl ester via epimerization, modified Curtius' rearrangement and sulfonylamino formation. Other derivatives may be prepared similarly.
Synthesis of Nitrated Analogs of Distamycin and their DNA Cleaving and Protecting Activities under UV Irradiation
Authors: Xiao Junhua , Yuarf Gu , Huang Weiqiang , Lum John H. K. , Lee K‐L Daniel , Chan Albert S. C. 
Published: May 2015

AbstractTwo nitrated analogs of distamycin were synthesized by a novel haloform reaction and the DCC/HOBT coupling reaction in a convenient and effective way with out amino group protection. Our results have demonstrated that these polyamides show DNA cleaving activity under long UV (LUV 365 nm) irradiation. Furthermore, it is an unexpected discovery that these analogs can prevent DNA dam age under short UV (SUV 302 nm).
A New Sesquiterpene, α‐Santalane‐11,12,13‐Triol from the Root Bark of Severinia Buxifolia in Hainan
Authors: Cherf Chien‐Mao , Lin Fu‐Wen , Kuo Ping‐Chung , Shi Li‐Shian , Wang Jhi‐Joung , Wu Tian‐Shung 
Published: May 2015

AbstractAnew sesquiterpenoid, α‐santalane‐11,12,13‐triol, together with thirty known compounds were isolated and characterized from the root bark of Severinia buxifolia in Hainan. Their structures were determined by spectroscopic methods. The relationship between constituents and collecting area is also discussed.
On Structural Parameterization and Molecular Modeling of Peptide Analogues by Molecular Electronegativity Edge Vector (VMEE): Estimation and Prediction for Biological Activity of Dipeptides
Authors: Li Shengshi Zhiliang , Fu Bianhong , Wang Yuanqiang , Liu Shushen 
Published: May 2015

AbstractBased on the distance between atoms and the electro‐negativity of each atom, a new set of descriptors called the molecular electronegativity edge vector (VMEE) being applied to de scribe the molecular structure of peptide analogues, is proposed only from the primary structure of peptides. Here several quantitative structure activity relationship models are proposed on the biological activity of 58 angiotensin converting enzyme (ACE) inhibitors and of 47 bitter tasting dipeptides by multiple linear regression method. The results show that the novel molecular electronegativity edge vector (VMEE) has both excellent structural selectivity and good activity estimation. Besides, this novel molecular electronegative edge vector, be cause it is easy to calculate, will be useful in structure characterization and activity prediction of biological molecules.
Synthesis of Thymidine Dimer Containing Novel (N‐Acetyl)imino Linkage
Authors: Yang Te‐Fang , Chien Fang‐Chi , Chung Fen‐Yu 
Published: May 2015

AbstractBy starting with 3′‐keto‐5′‐O‐protected thymidine, 3′‐O‐amino‐5′‐t‐butyl‐diphenylsilyl thymidine (9) was prepared and coupled with 3′‐O‐t‐butyl‐diphenylsilyl‐5′‐formyl thymidine to form a nucleoside dimer (11) containing oxime linkage. The back bone of this dimer, then, under went reduction followed by acetylation to give an (N‐acetyl)imino linkage, and a novel dinucleotide (13) was obtained.
Application of Laser‐Enhanced Ionization Spectroscopy: Effect of Dissociation Constant on the Atomization Efficiency Determination in an Acetylene‐Air Flame
Authors: Ke Ching‐Bin , Lu Shme‐Ing , Lin King‐Chuen 
Published: May 2015

AbstractBy using laser‐enhanced ionization (LEI) technique, we have studied atomization efficiencies of the alkalihalides in an acetylene/air flame. As an aqueous solution of the metal salt was nebulized into the burner head, a flame with a high temperature of about 2500 K may cause dissociation of the ionic bond to release the free metal atoms. The ratio of the number density of free metal atoms present in the flame to the total number density of the same metal element nebulized determines the atomization efficiency. In this work, binary salt solutions including LiX, NaX, and KX (X=Cl, Br, and I) were used; each was prepared at 5 ppm (μg/mL) metal concentration. The atomization efficiency of the metal element was measured, as the accompanied halogen species was varied. We found that the ratios of atomization efficiencies of the akalielement in different halide compounds were almost equal to one. Atomization efficiency determination is dominated by the metal atom, but weakly influenced by the binding halogen species. The observation may be interpreted satisfactorily by using the Sugden‐Bulewicz model. Based on this model, the metal atomization efficiency for different halide compounds depends on the number densities of the halogen atoms and the related dissociation constants. For the binary salt with a small concentration and a large dissociation constant, the atomization efficiency determination tends to be dominated by the metal atom alone.
Solvolysis of 1‐tert‐Butyl‐1‐(4‐phenoxyphenyl) Methyl Bromide and Chloride. Further Example for Possible Contribution of Non‐canonical Resonance Structure in the Transition State
Authors: Liu Kwang‐Ting , Chuang Chih‐Shiow 
Published: May 2015

AbstractThe solvolysis of 1‐tert‐butyl‐1‐(4‐phenoxy)methyl bromide (5b) and chloride (5c) in a variety of solvents were carried out. Limiting SN 1 mechanisms were suggested from the observation of linear relation ships using single‐parameter Winstein‐Grunwald type correlation between logarithm of rate constants with YxBnBr and YxBnCl scales, respectively. This result indicated positive charge delocalization over both arylrings and provided further evidence for possible contribution of non‐canonical resonance structure in the cationic transition state.
On Polarizability Effect of Alkyl Substituent
Authors: Li Shengshi Zhiliang , Yuan Xiaoyan , Wang Yuanqiang , Cao Chenzhong , Liu Shushen 
Published: May 2015

AbstractThe relative polarizability effect of alkyl substituent can be conveniently obtained by calculating the so‐called Polarizability Effect Index (PEI) value, pro posed firstly in our laboratories, PEI = Σ (α/Ni2), where ai is the polarizability of primary units CH3, CH2‐, CH< and >C‐, and the Ni is the carbon atom number from reaction site to the primary unit. By using the PEI and atomic charge in a molecule, the ionization potential of alkyl halide, the enthalpy of reaction for the gas‐phase addition of a proton to an alcohol or ether (proton affinity), the gas‐phase basicity of alcohols or ethers (proton affinity), and gas‐phase acidity of alcohols can be quantitatively modeled by the two‐parameter expression equation.
Microfabricated Electrophoresis Chips on Quartz Substrates and Their Applications on DNA Analysis
Authors: Lee Gwo‐Bin , Chen Shu‐Hui , Lin Chin‐She , Huang Guan‐Ruey , Lin Yen‐Heng 
Published: May 2015

AbstractDesign and fabrication of microcapillary electrophoresis (CE) chips on quartz substrates are described. The micro capillary channels are formed by the combination of a metal etch mask and wet chemical etching. In this paper, a simple but reliable one‐mask process is applied to fabricate micro structures on quartz substrates, which are commercially‐available blank photomasks. The selection of the quartz substrates greatly simplifies the fabrication process. The substrates with micro channels are then bonded with an other quartz cover plate at low temperature by using diluted hydrofluoric acid (HF) solution. Good channel sealing is observed. The low temperature bonding yields low residual stress and makes chemical surface modification prior to bonding feasible, if necessary. The quartz chips with higher UV transmittance allow us to use a laser induced fluorescence detection system for chemical analysis successfully. Solutions containing Nile blue are first per formed in the CE chips as a demonstration of electrophoretic injection. The capability of the microfabricated CE chips for electrophoretic injection and separation is then characterized via the analysis of DNA fragments φX174 digested by Hae III. An excellent signal/noise ratio is obtained. In addition to single‐channel sample injection and separation, multi‐channel de vices capable of parallel electro‐migration of multi‐samples have also been demonstrated in the study.
Cycloaddition of α‐Chloroformylarylhydrazines' with Pyridines Afford 2‐Aryl‐2H‐[1,2,4]triazolo[4,3‐a]pyridin‐3‐Ones
Authors: Chiu Chun‐Yen , Kuo Chao‐Nan , Kuo Wen‐Fa , Yeh Mou‐Yung 
Published: May 2015

Abstract2‐Aryl‐2H‐[1,2,4]triazolo[4,3‐a]pyridin‐3‐ones 4 were synthesized by cycloaddition of α‐chloroformylarylhydrazines 7 with pyridines 1. The inductive and mesomeric effects of substituents on pyridines were also investigated in this study. In reactions of 3‐substituted pyridines bearing a π‐electron‐donating substituent, the ortho site, C(2), of the pyridine ring is more favored for cycloaddition than the para site, C(6). As the substituent is a σ‐electron‐donating group, the cycloaddition only occurs on the ortho position. For reactions of 2‐substituted pyridines, however, cycloadditions were controlled solely by inductive effect, regard less of mesomeric effect. Only when the substituent is an electron‐donating group, would the cycloaddition proceed to afford expected cycloadducts. Further more, it is found that the inductive effect plays a more important role than the steric effect for reactions using 2‐substituted pyridines.
Fusicoccane Diterpenoids and Bisbibenzyls from the Liverwort Plagiochila Peculiaris
Authors: Wu Chia‐Li , Liou Chuang‐Shing , Ean Uni‐Juni 
Published: May 2015

AbstractTwo new oxygenated diterpenes, fusicoccanin and neofusicoccantriepoxide, were isolated and identified from the Taiwanese liver wort Plagiochila peculiaris. The latter compound possesses a methyl‐rearranged fusicoccane skeleton. In addition, known secoaromadendranes and macrocyclic chloro‐bisbibenzyls were also isolated from the polar fraction. P. peculiaris rep resents a very complex chemo‐type of this genus.
Annocherine C, A New C‐α Hydroxy Benzylisoquinoline and Other Constituents from the Leaves of Annona Cherimola
Authors: Chen Chung‐Yi , Wu Yang‐Chang 
Published: May 2015

AbstractA new C‐α hydroxy benzylisoquinoline, annocherine C (1), along with nine teen compounds including six alkaloids, liriodenine (2), oxoxylopine (3), oxonantenine (4), (‐)‐asimilobine (5), (‐)‐xylopine (6) and (‐)‐anolobine (7); four steroids, β‐sitosterol, stigmasterol, β‐sitosteryl‐D‐glucoside and stigmasteryl‐D‐glucoside and nine benzenoids, methylparabene, vanillin, trans‐methyl p‐coumarate, cis ‐methyl p‐coumarate, p‐hydroxybenzadehyde, p‐hydroxybenzoic acid, 4‐methoxybenzoic acid methylester, methyl vanillate and p‐dihydrocoumaric acid, were isolated from the leaves of Annona cherimola. These compounds were identified by spectral analysis.
Simple Fourier Trans form(FT)‐IR and Reverse‐Phase HPLC Identification Methods of Commercial Ganoderma Products
Authors: Chen Deng‐Hai , Ju Huei‐Yen , Hseu Kuo‐Chong 
Published: May 2015

AbstractGanoderma products could be classified into 3 types according to their raw materials, i.e. fruit bodies, cultured mycelia and the mixtures of both. Seven commercial samples and three mycelia products prepared in laboratory were analyzed by Fourier Trans form(FT)‐IR spectrophotometer. The fruit‐body products gave a weak absorption band at 890∼894 cm−1 and the mycelia show a weak to medium band at 774∼778 cm−1 on the FT‐IR spectra, respectively. These two bands were observed in the IR spectra of mixed‐type products. A modified sample pretreatment procedure for the reverse‐phase HPLC analysis was also investigated. The spectral patterns revealed that fruit bodies of the commercial samples were the species of G. tsugae.