bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass Spectrometric Analysis of Laser Induced Microplasmas from Organic Samples
Authors: Nitsche R. , Kaufmann R. , Hillenkamp F. , Unsöld E. , Vogt H. , Wechsung R. 
Published: November 2013

AbstractA Laser Microprobe Mass Analyser (LAMMA) has been developed for the analysis of microscopically small volumes (10−11–10−13 cm3) of thin organic specimens (0.1–1 μm). Detection limits for most of the organic ions are in the range of 10−17–10−20g corresponding to 0.1–10 ppm. The instrument is based on the combination of a light microscope for observation and exact localisation of the sampled volume within the morphological structures of the specimen as well as for focusing the beam of a pulsed laser onto the specimen. The ions of the laser‐generated microplasma are analysed with a time‐of‐flight mass spectrometer. Mass spectra of organic standard samples and heart muscle cells are reported and discussed.
Rapid Analysis of Therapeutic Drugs in Blood by Chemical Ionization Mass Spectrometry
Authors: Lehrer Michael , Karmen Arthur 
Published: November 2013

AbstractA rapid procedure was devised for analyzing anticonvulsants in serum by chemical ionization mass spectrometry. Samples were volatilized by heat into the ion source of the mass spectrometer and reacted there with CH5+ and other reactant ions produced by ion‐molecule reactions of the methane reagent gas. Increasing the temperature of the probe produced quasimolecular ion peaks of the different drugs, which rose and fell on the oscilloscope tracing at overlapping rates, indicating similar but not identical rates of volatilization. These peaks were recorded by connecting the electron multiplier ion detector output through a voltage to frequency converter to a 200 channel multichannel analyzer (MCA) operated in the multiscale mode. The concentration of the anticonvulsants were then calculated from the ratio of the counts in the channel of the drug to that of the appropriate internal standard. Other drugs present, including barbiturates, carbamazepine, ethosuximide and caffeine were readily identified when present. With one solid probe inlet, an assay could be performed every two minutes.
Use of Polymers as Protecting Groups in Organic Synthesis. VII. Preparation of Monobenzoates of Acyclic Triols
Authors: Fréchet Jean M. J. , Seymour Elizabeth 
Published: November 2013

AbstractCrosslinked resins containing styrylboronic acid units were used in the protection of 1,2 and 1,3‐diol groupings with several acyclic triols. With 1,2,3‐propanetriol, a five‐membered ring boronate was formed almost exclusively while with 1, 2, 4‐butanetriol a six‐membered ring boronate predominated. The fully recyclable polymer could be used in a fast and efficient synthesis of monobenzoyl derivatives of triols. Macroreticular and 1% crosslinked solvent‐swellable resins were tested and the latter were found to perform better on repeated use.
A Graphite Supported Chiral Catalyst
Authors: Kagan H. B. , Yamagishi T. , Motte J. C. , Setton R. 
Published: November 2013

AbstractPartially graphitized carbons were functionalized by carboxylic groups which were esterified with 4‐hydroxybenzaldehyde. A chiral diphosphine moiety, analogous to the DIOP framework, was then synthesized from the aldehyde function. The supported chiral diphosphine was transformed into a rhodium catalyst. Preliminary results of asymmetric hydrogenation or asymmetric hydrosilylation are described.
Some Recent Advances in the Study of the Reactivity of Systems Containing Polymers
Authors: Morawetz Herbert 
Published: November 2013

AbstractRecent studies of reaction rates in polymer systems are reviewed. These involve ionic reactions in polyelectrolyte solutions, kinetic effects due to the nature of the “effective solvent medium” in the polymer domain, neighboring group effects in polysaccharide oxidation, intramolecular polymer reactions involving non‐neighboring groups, the quenching of the fluorescence of groups attached to a polymer by species carried by another polymer chain and the photoisomerization of azobenzene residues in the backbone of polymer chains.
Enzyme–Analogue Built Polymers. IX. Polymers with Mercapto Groups of Definite Cooperativity
Authors: Wulff Günter , Schulze Ilona 
Published: November 2013

AbstractBy copolymerization of bis(p‐vinylbenzyl)disulfide (1) with crosslinking monomers and subsequent reduction of the disulfide bond with diborane, polymers with two closely positioned mercapto groups were prepared. Under comparable conditions polymers with randomly distributed mercapto groups were obtained from (p‐vinylbenzyl)thioacetate (2). The degree of cooperativity of the mercapto groups in polymers of (1) as well as the degree of site separation in polymers of (2) were determined quantitatively by oxidation with I2. The percentage of reoxidation by I2 to disulfide depends on degree of crosslinking of polymer, the concentration of mercapto groups, the degree of swelling and the reoxidation temperature. From these data valuable information on the arrangement of functional groups as well as on polymer structure was obtained.
Synthesis of Potential Biologically Active Polymers Based on Polystyrene
Authors: Gabbay Y. , Zilkha A. 
Published: November 2013

AbstractPolystyrene was utilized as a polymer backbone on which various potentially biologically active structures were constructed. The polymer was chloromethylated and converted by a series of reactions to polyphenethylamines, polyphenylacetamides and a polybarbiturate.
Impregnated Resins: Metal‐Ion Complexing Agents Incorporated Physically In Polymeric Matrices
Authors: Warshawsky Abraham , Patchornik Avraham 
Published: November 2013

AbstractSolvent Impregnated Resins (SIR) are prepared by physically impregnating metal‐active compounds in high‐surface area, macroporous, styrene‐divinylbenzene copolymers. Impregnation methods, the structure of the resulting SIR resins, and their metal complexing properties are examined. The interrelationships between complexation efficiency, the nature of the extractant, and its concentration in the polymeric phase is discussed. Three practical examples of ion separation are discussed using solvent impregnated resins incorporating di‐2‐ethylhexylphosphoric acid, tri‐butyl‐phosphate, and 2‐hydroxyaryloximes.
The Effect of Adsorption Conformation of Intermediates on Kinetic Parameters of Electrode Reactions. Mechanism of the Electroreduction of Dihalopyridines on the DME
Authors: Kashti‐Kaplan S. , Kirowa‐Eisner E. 
Published: November 2013

AbstractThe mechanism of reduction of 2,6‐dichloropyridine, 2,5‐dibromopyridine and 2,3‐dichloropyridine in ethanol‐water media was investigated at the DME. The electrode processes were studied by measurements of Tafel slopes, reaction orders and pH effects. The proposed mechanism involves: (i) first protonation and electronation in a quasi‐equilibrium step resulting in an adsorbed pyridinyl radical (intermediate I) parallel to the electrode surface, (ii) Cleavage of the C–X bond in the rate‐determining step, resulting in an adsorbed cation radical (intermediate II), perpendicular to the electrode. The Tafel slope computed via the combined‐adsorption isotherm are in agreement with the experimental values.
Multiscreen Carbon Cloth Electrode
Authors: Sutzkover E. , Zur C. , Ariel M. 
Published: November 2013

AbstractThe current—voltage response of single and multiscreen electrodes for a limited range of electrolyte flow velocities is described. The short and long term stability of the single screen electrodes and their performance under a variety of operating conditions were determined. The multiscreen electrode was next examined to determine resistances within the cell, which were then exploited for the interpretation of current distributions and concentration profiles obtained with the multiscreen electrode operating in the rear or the frontal supply mode.
Anisotropy of the Optical Properties of Electrode Surfaces
Authors: Plieth W. J. 
Published: November 2013

AbstractDifferential reflection spectroscopy of electrode/electrolyte interfaces gives a quantity which in analogy to thermodynamic properties of the surface region shall be called “dielectric surface excess”. The dielectric surface excess has two complex components representing the anisotropy between the dielectric properties tangential and normal to the surface. Methods are described for the experimental determination of the two components. Results for oxide layers on platinum, bromide adsorbed on gold, rhodamin B adsorbed on silver and monomolecular films of lead on silver are discussed.
Study of the Adsorption of Succinic Acid on Platinized Platinum Electrode by Radiotracer Method
Authors: Horányi G. , Rizmayer E. M. , Inzelt G. 
Published: November 2013

AbstractThe problem of the adsorption behaviour of succinic acid has been studied from different points of view. The mobility of adsorbed species, the potential dependence of the adsorption and the effect of different ions and organic species on the adsorption were investigated in M HClO4 supporting electrolyte using platinized platinum electrode. It has been stated that succinic acid does not chemisorb under the experimental conditions studied, and it may be considered as a typical representative of organic compounds which behave like anions with respect to the adsorption properties. An attempt was made to explain the unexpected potential dependence of the adsorption of these species.
Adsorbed Hydrogens and Reduction of Olefins on Platinum in Acid Solution
Authors: Kita Hideaki 
Published: November 2013

AbstractPlatinum electrodes subjected to anodic activation reveal three kinds of adsorbed hydrogen (I, II, and III). These adsorbed hydrogens are interchangeable with each other. The adsorbed hydrogen I (ionization peak at ca. 40 mV, rhe) is the most reactive and responsible for the hydrogen evolution reaction. When C2–C4olefins are reduced by H2, the adsorption layer on Pt drastically changes depending on the composition of olefin and H2in the gas phase. At relatively low pressure of H2(region H), II (ca. 140 mV) takes part in the hydrogenation, whereas III (ca. 290 mV) gradually changes to II. Isotopic study proves that the hydrogenation in region H proceeds by the two Horiuti‐Polanyi type reaction paths, which is common among the olefins studied. The electroreduction gave the same results, where the discharge of H+is always taken to be in equilibrium.
Study of Nonconjugated Bichromophores Linked by a Polyether Chain. I. Photochemical Synthesis of Crown‐Ethers from bis‐(9‐Anthryloxy) Polyoxaalkanes
Authors: Desvergne Jean‐Pierre , Bouas‐Laurent Henri , Sarrebeyroux Roland 
Published: November 2013

AbstractA series of bisanthracenes (In) linked by a polyoxyethylene chain: 9‐anthryl‐O–CH2–CH2–O–CH2–(CH2–O–CH2)n–CH2–O‐9‐anthryl, where n = 1–4, was synthesized in order to investigate the bichromophoric interactions of the two aromatic rings in connection with the special properties of the chain. UV absorption spectra at room temperature in benzene and ethanol exhibit, in general, a weak hypochromicity compared with other 9–9′ bisanthracenes. Under the same experimental conditions, the fluorescence of In is twofold: (i) an emission from the locally excited state (“monomer fluorescence”) with quantum yield (ΦFM) ca. 0.10–0.17 (benzene) and 0.03–0.08 (ethanol); (ii) an excimer‐type fluorescence centered at ca. 470–515 nm, of which quantum yields (ΦFD) are in the range 0.01–0.025 (benzene) and 0.01–0.012 (ethanol). Of note is the observation of an intramolecular excimer formed from bischromophores linked by long chains (10–19 atoms). Photocyclomerization quantum yields were found to be (365 nm) 0.18–0.26 (benzene and ethanol); closure effiency is almost as high as for bisanthracenes linked by short chains. The photocyclomers, thermally unstable, are readily dissociated to In at room temperature. Several closure and reopening cycles could be observed in degassed diluted solutions. Under our conditions, addition of inorganic salts such as LiClO4 does not distinctly alter closure quantum yields of In. Rather, the complexes formed between the photocyclomers IIn (crown‐ethers) and the cations are thermally stable up to high temperatures and were not observed to revert to In either thermally or by irradiation with a low pressure mercury lamp. But the compounds In were quantitatively recovered with an excess of polar solvents which compete with the crown‐ethers to solvate the cation.
Ligand Structure and Complexation, XLVIII Alkali and Alkaline Earth Metal Ion Complexes of Bipyridine, Phenanthroline and Terpyridine
Authors: Vögtle Fritz , Müller Walter M. , Raßhofer Werner 
Published: November 2013

AbstractCrystalline alkali and alkaline earth metal ion complexes of 2,2′‐bipyridine and 2,2′:6′,2″‐terpyridine are obtained and compared with known and new alkali and alkaline earth metal salt complexes of 1, 10‐phenanthroline.
Crown Ether Assisted Chemical Reactions, II. Crown Ether Complexes of Potassium Phthalimide, Sodium Saccharinate and Sodium Acetylacetonate: New Reagents Containing Activated Anions
Authors: Raßhofer Werner , Oepen Gerhard , Vögtle Fritz 
Published: November 2013

AbstractThe synthesis of several crown ether and cryptand complexes with potassium phthalimide, sodium saccharinate and sodium acetylacetonate is reported. The anions in the complexes prove to be activated; this has been used to carry out a series of new nucleophilic substitutions with 2,4‐dinitrochlorobenzene, pentachloropyridine and pentafluoropyridine. Without addition of crown ethers these reactions could not be achieved. Only pentafluoropyridine reacts with potassium phthalimide alone, yielding a monosubstituted product. With crown ether assistance threefold substitution could be realized with pentafluoropyridine, whereas pentachloropyridine gave only monosubstitution.
Wrapping of Metal Cations by Linear Polyethers
Authors: Saenger W. , Suh I.‐H. , Weber G. 
Published: November 2013

AbstractThe wrapping of linear polyethyleneglycol ligands around metal cations is dependent on their lengths. Short ligands (containing 5 heteroatoms) form circular complexes; extension by one to five heteroatoms leads to helical structures, and ligands containing 11 heteroatoms are able to bind two cations in an S‐like arrangement. It is remarkable (1) that the longer achiral ligands form chiral complexes, (2) that in general all the heteroatoms are coordinated to the cation, (3) that the cation … heteroatom distance is dependent on the electronegativity of this atom, (4) that the C–C–O–C and C–O–C–C torsion angles are trans while the O–C–C–O are gauche, (5) that while the O–C–C–O torsion angles are always gauche the C–C–O–C and C–O–C–C are more flexible and can adopt a non‐trans form, and (6) that the ligands wrap preferentially in an “equatorial” zone around the cation while the “polar” zones are occupied by one or both ends of the ligands depending on their lengths. In this study we describe the molecular structures of the following complexes as determined by X‐ray crystallographic methods: the RbI‐complexes of α, ω‐bis(8‐quinolyloxy)‐3‐oxapentane, and of the homologous – 3, 6, 9‐trioxaundecane and ‐3, 6, 9, 12, 15, 18‐hexaoxaeicosane; the RbI‐complex of 1, 11‐bis(8‐quinaldyloxy)‐3, 6, 9‐trioxaundecane; the NaSCN‐complex of 1, 8‐bis(2‐methoxyphenoxy)‐3, 6‐dioxaoctane; and the 2 · KSCN‐complex of 1, 5‐bis{2‐[5‐(2‐nitrophenoxy)‐2‐oxypentyloxy]‐phenoxy}‐3‐oxapentane.
Enzyme‐Analogue Built Polymers XII Specific Binding Effects in Chiral Microcavities of Crosslinked Polymers
Authors: Wulff G. , Lohmar E. 
Published: November 2013

Abstract2,3‐O‐(4‐Vinylphenylboronic)esters (2a–c) of different D‐glyceric esters were copolymerized to macroporous, crosslinked polymers. After the glyceric esters 1a–c, acting as templates, had been split off, chiral microcavities with one boronic acid group per cavity were formed. These polymers were capable of resolving the racemate of the template used. By comparison of resolution‐specificities of polymers prepared from glyceric esters carrying different bulky groups in the ester moiety, the influence of the size of substituents at the asymmetric C could be determined. The polymers showed the most specific racemic resolution for the racemate of the template used. Small differences between the structure of the racemate and that of the template used led to a decrease of specificity; bigger differences resulted in a complete disappearence of specificity. Furthermore, it was investigated whether non‐covalent interactions between the template and added comonomers were strong enough during polymerization to allow the formation of specific structures within the cavities. The directed introduction of charge‐transfer interaction led to a strong increase in specificity for racemic resolution.
Conformational Analysis of Flexible trans‐Dienes by Polarization Spectroscopy
Authors: Sheves Mordechai , Friedman Noga , Levendis Demetrius , Margulies Leon , Mazur Yehuda 
Published: November 2013

AbstractThis paper presents our attempts to utilize polarized (linear dichroic) spectroscopy of compounds oriented in stretched films for the conformational analysis of labile systems.
Monolayer Assemblies of Dyes to Study the Role of Thermal Collisions in Energy Transfer
Authors: Möbius Dietmar , Kuhn Hans 
Published: November 2013

AbstractThe energy transfer from an oxacyanine to a thiacyanine dye was investigated in monolayer assemblies. No temperature‐dependence of the efficiency was observed between 300 K and 20 K in arrangements where the donor molecules were isolated. However, in arrangements where the donor was organized into a large aggregate and the acceptor was highly diluted in the adjacent monolayer, the efficiency of the energy transfer was proportional to the absolute temperature; the spectral distributions of the fluorescence of the donor and the absorption of the acceptor were equally well matched at low and high temperatures. A simple model is discussed based on the idea that the energetic match needed for energy and electron transfer occurs occasionally due to thermal fluctuations and that this match will not be achieved below a certain temperature. A mechanism based on exciton hopping in the aggregate followed by energy transfer from a molecule in the vicinity of the acceptor to the acceptor does not explain the observed temperature‐dependence. However, the present experimental data can be rationalized by assuming that the excitation extends over a certain domain (consisting of about 10 donor dye molecules at room temperature and about 150 molecules at 20 K) which moves over the aggregate, occasionally reaching the vicinity of an acceptor molecule.
The Tetragonal Crystal Structure of 2:3 Deoxycholic Acid–Water Complex
Authors: Tang C. P. , Popovitz‐Biro R. , Lahav M. , Leiserowitz L. 
Published: November 2013

AbstractThe deoxycholic acid (DCA)–water (2:3) complex crystallises in space group P41212. The DCA molecules form hydrogen‐bonded layers which contain channels filled by chains of water molecules. These water molecules are linked by hydrogen bonds with each other and with the DCA molecules on the channel walls. The channel walls are thus hydrophilic unlike the hydrophobic channel walls found in the commonly observed orthorhombic P212121 inclusion complexes of DCA.
The Antisymmetrized Geminal Power, a Simple Correlated Wave Function for Chemical Bonding
Authors: Linderberg Jan 
Published: November 2013

AbstractThe pertinent features of the antisymmetrized geminal power are brought out with a view of describing the chemical bond and the electronic properties of molecules. It is demonstrated that for certain hamiltonians it is consistent with a response function derived from a simple moment expansion characteristic of the random phase approximation. Deficiencies with regard to “size consistency” are pointed out. Simple examples are analyzed in order to familiarize the reader with the nature of the approximations.
The Effect of Intramolecular Interactions on the Transferability Properties of Localized Descriptions of Chemical Groups
Authors: Bonaccorsi Rosanna , Ghio Caterina , Scrocco Eolo , Tomasi Jacopo 
Published: November 2013

AbstractStarting from a localized description of molecular wavefunctions, approximate descriptions of chemical groups are obtained. The degree of conservation of these representations is verified over a fairly large number of compounds by using different tests, from which it is seen that the influence of intramolecular interactions is strong enough to necessitate the inclusion of these effects in the description of molecular systems in terms of transferable models of groups. Further analyses demonstrate that intragroup interactions can be approximated, to a good degree of precision, by classical interactions only. The usefulness of a zeroth order representation of a group in terms of nonorthogonal transferable models of localized orbitals, coupled to an evaluation of classical intragroup interactions, is discussed, and a simple computational method for the evaluation of the changes in reaction barriers due to substitution of chemical groups in a given molecular framework is briefly outlined.
Walsh's Rules and the Small Bond Angle States of Triatomic Dihydride Molecules
Authors: Casida Mark E. , Chen Maynard M. L. , Macgregor Robert D. , Schaefer Henry F. 
Published: November 2013

AbstractA series of excited electronic states of AH2 molecules having extremely small bond angles has been discovered theoretically. Systems which have shown this characteristic to date include H2O+, NH2, CH2+, and NH2+. In the present research ab initio studies were carried out using a double zeta plus polarization basis set. Configuration interaction including all Hartree‐Fock interacting single and double excitations was performed. For the 2B2 state of CH2+, the predicted equilibrium geometry is θe(HCH) = 35.2°, re(C‐H) = 1.41 A. This state is bound by 20.3 kcal/mole relative to the separated C+ + H2 ground electronic state. The analogous state of BH2 is not substantially bound, but the neutral C + H2 system shows some very interesting features. All of these results may be qualitatively understood in the context of Walsh's rules.
Bonding in Metal Atom Cluster Compounds from the d‐Orbital Overlap Model to SCF‐Xα‐SW Calculations
Authors: Bursten Bruce E. , Cotton F. Albert , Stanley George G. 
Published: November 2013

AbstractThis paper gives a survey of results pertaining to the electronic structures of metal atom cluster compounds. The development of progressively more complete and accurate calculations, from the simple d‐orbital overlap model of Cotton and Haas (1964) through approximate Hartree–Fock (Fenske–Hall) calculations to recent SCF‐Xα‐SW calculations incorporating corrections for relativistic effects. It is shown that the qualitative essentials of the bonding are apparent even in the simplest treatment but that the more sophisticated methods are required to interpret spectra and other experimental data quantitatively.