bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Formation of Carbenium Ions and Naked Anions by the Protonation of Phthalophenone with a Super Acid
Authors: Brandner G. , Dickert F. L. , Lehmann E. 
Published: March 2014

AbstractTwo molecules of a strong acid such as CF3SO3H are necessary to cleave the lactone ring of phthalophenone. NMR and conductivity measurements reveal that the carboxylate group has to be protonated for this purpose followed by its solvation with an additional molecule of acid. But CF3SO3‐ which is simultaneously formed behaves as a naked anion in the solvent dichloromethane. CNDO‐Calculations indicate a strong interaction between the charged central carbon atom and the ‐COOH group in which is accompanied by an unusually large twisting of the phenyl rings.
Test of a Symmetry Reduced Extended RISM (XRISM) Equation Against Diffraction Experiments on Liquid Benzene and Hexafluorobenzene and Evaluation of Optimized Potentials
Authors: Bartsch E. , Bertagnolli H. 
Published: March 2014

AbstractSymmetry reduced extended RISM (XRISM) calculations have been performed on the polar molecular liquids benzene and hexafluorobenzene. By comparing XRISM results and Monte Carlo simulation data for benzene, good agreement between both methods could be shown applying different closures. Testing XRISM theory against X‐ray and neutron diffraction experiments, it could be demonstrated that the method is suited to extract optimized Lennard‐Jones (12,6) potentials. Although a good overall agreement with experimental data could be achieved, the remaining differences suggest that it is necessary to use more complicated potentials in order to obtain a full description of the structural details provided by the experiments. — A variation of the partial charges can be tentatively interpreted in terms of electrostatic interactions playing a decisive role in the determination of the short‐range structure in the studied polar molecular liquids.
Solid‐Solute Phase Equilibria in Aqueous Solution. I. Solubility Constant and Free Enthalpy of Formation of Huntite
Authors: Königsberger E. , Gamsjäger H. 
Published: March 2014

AbstractSolid binary carbonate phases often dissolve congruently in aqueous media, even when they are not stable under the prevailing conditions. From the thermodynamic point of view these dissolution reactions lead to a metastable equilibrium with fixed composition, when neither diffusion in the solid state nor recrystallization from the solution occurs. The solubility of natural huntite. CaMg3(CO3)4, was studied potentiometrically at 50°C and I = 3.0 mol kg−1 (Na)ClO4. Since it dissolved congruently the solubility constant log *Kpso = log{[Ca2+]0.25 [Mg2+]0.75 p[H+]−2} = 10.36 ± 0.03 was used to calculate its standard free enthalpy ΔfG0298 (Ca0.25Mg0.75CO3) = −1045.0 ± 2.4 kJ mol−1; thus huntite is considerably less stable than the corresponding mechanic mixtures of calcite or dolomite and magnesite respectively. Stable and metastable equilibria in carbonate systems can be graphically presented by phase diagrams with In *Kpso and mole fractions as variables, where *Kpso is the total solubility constant defined by *Kpso = ([Ca2+] + [Mg2+]) p [H+]−2.
Charge Carrier Generation and Transport in Polyvinylcarbazole: A Model System for Polymeric Photoconductors
Authors: Kaul H. , Haarer D. 
Published: March 2014

AbstractThe problem of electron‐hole separation in polyvinylcarbazole (PVK) is discussed, based on new “time of flight” data, covering a time range from 10 nanoseconds to about 10 minutes. The experimental data are analyzed with the aid of the Onsager‐theory of electron‐hole recombination and yield an Onsager radius r0 of 18 ± 2 Å. Due to the high sensivity of the method it is possible to reproduce the low field regime of the Onsager recombination scheme. There are still sizeable deviations between the theoretical and the experimental quantum yields in the mid field regime. These differences do not enter into the determination of the r,‐value to a great extent because ro shows a weak logarithmic dependence on the extrapolated low and high field values of the charge carrier yields. The discrepancies between theory and experiment are believed to be caused by inhomogeneous electrical fields due to localized space charges in the zone of charge generation; they may in future provide information about the magnitude of “internal fields”.
NQR Spectroscopy and Structure of Photochromic 2,3,4,4‐Tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline and 2,4,4‐Trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide
Authors: Brummer Stefanie , Weiss Alarich 
Published: March 2014

AbstractThe 35Cl NQR spectra of the photochromic compounds 2,3,4,4‐tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline. β‐TKN, and 2,4,4‐trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide, TCNS, were studied from 77 K to the decomposition temperature. The crystal structure of TCNS was determined, space group C‐P21/m, Z = 2, a = 818.3(2) pm, b = 828.0(2) pm, c = 905.4(2) pm, β = 107.552(2)°, σcalc = 1.752 Mg · m−3. No phase transition is observed for the two title compounds in the temperature range of the 35Cl NQR spectroscopy. The 35Cl NQR spectra are discussed in connection with the crystal structures. — For a few other compounds related to the photochromic ones, 2,2,3,4‐tetrachloro‐1‐oxo‐1,2‐dihydronaphthaline (α‐TKN), 2,3,4,4,5,6‐hexachloro‐cyclohexadiene‐(2,5)‐one‐(1) (HCP), 2,2,3,4,4‐pentachloro‐1‐oxo‐1,2,3,4‐tetrahydronaphthaline, and 2,3,4‐trichloro‐1‐naphthol, results of NQR spectroscopy are given, too.
In Situ Observation of a Phase Transformation in α‐(BEDT‐TTF)2I3 using a Contactless Technique
Authors: Späth K. , Gross F. , Heidmann C. P. , Andres K. 
Published: March 2014

AbstractWe describe a novel apparatus for contactless measurement of the conductivity of small platelet‐shaped charge transfer crystals from above room temperature down to helium temperatures. This technique is employed to study the temperature dependence of the conductivity in the quasi two‐dimensional organic conductor α‐(BEDT‐TTF)2I3 both in its pristine form and after annealing at 360 K. The low temperature behaviour is found to change from insulating (metal‐to‐insulator transition at 135 K) to metallic.
Single Crystals from Optically Active Diacetylenes and Polydiacetylenes
Authors: Kröhnke C. 
Published: March 2014

AbstractDiacetylene monomers with chiral side groups have been synthetized. The monomer crystals polymerize upon irradiation or thermal annealing. The thermal polymerization was studied and the potential use of the resulting polymer crystals as optical devices was discussed. A characterization of the monomers and one polymer in solution with regard to specific rotation was obtained.
Intrinsic Fluctuations in Macromolecular Self‐Replicating Systems
Authors: Fernandez Ariel 
Published: March 2014

AbstractThe relevance of stochastic effects at very low template concentration for Qß‐catalized‐template‐instructed RNA replication is established. The fluctuations in rates and in elongation intermediate concentrations are determined making use of a center manifold stochastic reduction of the fast‐relaxing kinetic degrees of freedom. The strength of these far‐from‐equilibrium fluctuations is scaled with the small rate‐control characteristic parameters of the system. The fluctuations in the concentration of the chain‐elongation intermediate complexes are enhanced as the template chain becomes shorter, thus, a deterministic description does not hold for RNA chains of the order of 50 nucleotides. Some results on the de‐novo synthesis of RNA are reinterpreted in the light of these experimental findings. The far‐from‐equilibrium fluctuations determine the scattering of lag‐times corresponding to the macroscopically‐detectable amplification of the template. The results show very good agreement with the experimental evidence.
Rechnergestützte Analyse komplexer NMR‐Spektren. Untersuchungen zur spektralen Darstellung und Vergleichsfunktion
Authors: Schäfer A. , Ziessow D. 
Published: March 2014

AbstractNMR Spectra of more than three strongly coupled spins need to be analyzed with the aid of iterative computer programs. Computation times and convergence depend on the employed measure V of similarity between experimental and theoretical data. The latter are calculated with suitably chosen values for the parameter vector p of the spin system so that V(p) constitutes an error function. Various functions are classified in terms of the representation of spectra and their properties are discussed along particular cross‐sections in the parameter space. This includes the dependence on the normalization of the theoretical spectrum (largest peak vs. integral) and kind of unsigned errors (squared vs. absolute value). Computation times and convergence behaviour show that broadened spectra and integral functions may well be used to represent the full spectrum, while triangular line shapes may be of advantage when transition frequencies and intensities are available only.
Nuclear quadrupole interactions in solids: A survey
Authors: Smith J. A. S. 
Published: March 2014

AbstractNuclear quadrupole interactions have been measured in solids for nearly forty years; with recent improvements in techniques and sensitivity, they are finding much application in the study of electronic structure and molecular motion. The most complete information on the quadrupole coupling tensor comes from investigations of single crystals as in recent 35Cl quadrupole resonance studies in low magnetic fields of 1,2‐dichloro‐3‐nitrobenzene and (CH3)3C.CO2SbCl4 and in high magnetic fields of 17O magnetic resonance in benzophenone. High‐field studies of quadrupole splitting in the nuclear magnetic resonance spectra of powders are becoming increasingly used, particularly 27Al interactions in minerals and zeolites and 2H splittings and their relation to structure and motion in polymers. The sensitivity of radiofrequency techniques can be considerably increased by the use of double resonance methods, illustrated by recent work on 17O quadrupole interactions in O — H…O hydrogen bonds, 7Li of defects in lithium metal, and 14N in the detection of disorder in p‐nitrobenzoic acid crystals. Nuclear methods have an important part to play because of their remarkable sensitivity; the use of Mössbauer spectroscopy in the study of Fe(0) clusters and perturbed angular distribution techniques to measure 19F quadrupole interactions by means of an excited nuclear state of spin 5/2 provide interesting examples. Finally, recent theoretical and experimental work has been attempting to resolve the important question of the extent of charge transfer in ionic solids, illustrated by recent 57mFe studies of α‐Fe2O3 and 7Li, 14N in the superionic conductor Li3N.
79,81Br and 127I NQR studies of hydrobromides and hydriodides of amino acids and dipeptides
Authors: Kehrer Armin , Fleck Silvia , Weiss Alarich 
Published: March 2014

AbstractBy 79,81Br and 127I NQR the hydrobromides of 1‐asparagine, 1‐asparatic acid, glycyl‐1‐alanine, and glycylglycine and the hydriodides of 1‐asparagine, 1‐glutamic acid, and glycylglycine were studied in the temperature range of 77 ≤ T/K ≤ 420 (or decomposition point). — A reversible phase transition is observed for glycyl‐1‐alanine hydrobromide at 203 ± 1 K. 79,81Br NQR frequencies are strongly influenced by N⊕—H…Br⊖ and O—H…Br⊖ hydrogen bonds. The 79Br frequencies can be grouped into two bands, one at 12.4 < v/MHz < 18.5, the other at 24.8 < v/MHz < 26.4. The compounds of the high frequency group are characterized by N⊕—H…Br⊖ and O—H…Br⊖ hydrogen bonds, whereas the bond scheme of the low frequency compounds is determined by N⊕—H…Br⊖ bonds only. This grouping of amino acid and dipeptide hydrobromides according to frequency band and hydrogen bond scheme can be applied to the hydriodides, too. The ones with a O—H…I⊖ hydrogen bond have nuclear quadrupole coupling constants of N⊕ > 120 MHz, the other compounds with N⊕—H…I⊖ hydrogen bonds only show nuclear quadrupole coupling constants of 70 < e2QzzQh−1/MHz < 120.
Optical solid state spectroscopy by holographic grating techniques with quantum limited sensitivity
Authors: Bráuchle Chr. 
Published: March 2014

AbstractIn the past holographic gratings have been used successfully with cw and pulsed laser sources to study a broad variety of photophysical and photochemical phenomena of molecules in solid, liquid and gas phase. In this paper a newly developed holographic grating technique, called phasemodulated holography (PMH), is presented. With this technique for the first time a separated and simultaneous monitoring of the amplitude and phase gratings including the absolute signs of these contributions is possible. Thus hologram formation mechanisms and the underlying photochemistry can be studied in great detail. This feature and an up to eight orders of magnitude improvement of detection sensitivity over conventional techniques makes PMH an ideal tool for the investigation of new materials for holographic optical information storage. This will be demonstrated for several examples i. e. photoactive molecules incorporated in polymer systems.
Photophysical hole burning on dye solutions in the liquid phase with ns‐laserpuises
Authors: Menzel Ralf , Witte Peter 
Published: March 2014

AbstractThe necessary conditions for observing inhomogeneous bleaching of the electronic absorption bands of organic molecules in solution at room temperature have been investigated by simple rate equation models. For systems with ground state recovery times in the ps‐range, photophysical hole burning (PPHB) can be obtained with the ns‐laserpulses. The measured experimental result for crystal violet in acetonitrile may serve as an example. In transitions between excited states PPHB is possible as an universal method on probably all organic molecules. This has been demonstrated for the S1‐absorption band of para‐terphenyl at 570 nm. The given brief outline of methods, results, and conclusions will be described separately in more detail.
Diffusion of excess electrons in decomposing liquid metal‐ammonia solutions in the high‐conducting state, injected into a zero‐electric field space
Authors: Arendt P. 
Published: March 2014

AbstractThe diffusive motion of electrons in the high‐conducting state of decomposing liquid lithium‐ammonia and sodium‐ammonium solutions in response to a non‐uniform concentration of electrons has been investigated. Excess electrons are produced near a permeable anode and through it injected into a zero‐external electric field space behind the anode. The excess electrons diffuse away from the anode over an average distance of about 1.5 cm during their lifetime in the high‐conducting state, which indicates through the Nernst‐Einstein relation a very large electric mobility of the electrons.
New strategies for studies on the kinetics and energetics of the Belousov‐Zhabotinskii reaction
Authors: Koch E. , Nagy‐Ungvarai Zs. 
Published: March 2014

AbstractThe oscillatory Belousov‐Zhabotinskii reaction and its subsystems were studied by ≈ 1700 DTA and UV experiments performed at linearly increased temperature. The starting concentrations of bromate, bromide, catalyst, and malonic acid were varied in order to obtain “concentration codes” of such series. These represent the dependence of any parameters in discrete ranges of the starting concentrations of the different components. Particularly adequate for a model check are the mechanistic codes (=MCC's), which concern the shape index and reaction type index: If these mechanistic coordinates remain constant in such a concentration interval, other data, e.g. activation energies, can be attributed to a rate‐determining process. — The results led to a nine‐step model which is based on the FKN mechanism and is capable of roughly reproducing the influence of the initial concentrations and heating rate on 11 parameters characteristic of the envelope and of the oscillations of the experimental signals. The MCC's of the experimental and theoretical series are similar, revealing 4 — 5 rate‐determining steps in the different concentration ranges.— The activation energies agree with values from the literature, cited for three steps; these and further resulting activation energies are consistent with our studies with subsystems.
Thermodynamic analysis of partition data in the CaCl2‐H2O‐n‐Octanol and CaCl2‐H2O‐n‐butanol systems at 298.15 K
Authors: Apelblat Alexander , Manzurola Emanuel 
Published: March 2014

AbstractSimultaneous extraction of calcium chloride and water by n‐octanol and n‐butanol is described. In the system with n‐octanol, the experimental results are consistent with formation of partly dissociated CaCl2(H2O)5(ROH)5 complex in the organic phase. The equilibrium constant for complex formation is K = 6.3 · 10−7 mol−1 kg. In the case of n‐butanol, only at low concentrations of calcium chloride, the extraction can be represented by formation of CaCl2(H2O)7(ROH)8, complex with K = 0.056 mol−1 kg. Activities of alcohols in the organic phase were evaluated by a numerical integration of the Gibbs‐Duhem equation. The solubility of water in n‐butanol as a function of water activity was also determined.
A New Statistical Model for Adsorption of Mixtures on Heterogeneous Surfaces
Authors: Liedy W. , Schlünder E.‐U. 
Published: March 2014

AbstractA new model for adsorption equilibria on heterogeneous surfaces is developed. First an analytical equation for single‐component adsorption is derived. Then the model is extended to mixtures. The comparison with experimental data shows that single‐component data can be described and extrapolated in a wide pressure and temperature range. The mixture data of a strongly real adsorpt system can be predicted with good accuracy only from single‐component sorptive data and the vapor‐liquid equilibrium of the considered system. A simplified model with mixture parameters gives good extrapolation to other temperatures.
Counterion Accumulation in Rod‐Like Polyelectrolyte Solutions with Added Salt and Manning's Condensation Theory
Authors: Bizzarri A. R. , Cametti G. , Di Biasio A. 
Published: March 2014

AbstractThe Poisson‐Boltzmann equation in the cylindrical cell model is solved numerically for charged polyelectrolyte solutions containing mono‐ or di‐valent counterions and mono‐valent coions. The results, which describe the ion distribution around the polyion, are compared with those derived from the Poisson‐Boltzmann equation for salt‐free solutions in the limit of infinite dilution and with the Manning counterion condensation theory. This approach generalizes the results of Le Bret and Zimm for the dependence of the condensation radius on the polyion concentration to polyelectrolyte solutions containing added salt and shows how counterion condensation occurs even at finite concentration. The general conclusion drawn not only supports further evidences that the Manning condensation theory can be deduced from the Poisson‐Boltzmann equation but also suggests that counterion binding changes progressively from a free to condensed phase, as the polyion charge density parameter increases.
The Kinetics of the Interfacial Diffusion Controlled Electrochemical Processes at Non Porous Electrode/Solid Electrolyte Interfaces of Finite Dimensions
Authors: Barbi G. B. , Beonio‐Brocchieri F. 
Published: March 2014

AbstractThe functional dependence of current density and overpotential for an electrochemical process taking place at the interface between a “blocking” electrode and a solid electrolyte and whose rate determining step is the tangential diffusion over the interface was evaluated. — The conditions of applicability to such systems of the classical electrochemical kinetics were criticized. — In particular, it was put into evidence that, even in the case of a linear trend between the logarithm of the current density and overpotential, the extrapolation of the straight line portion to zero overpotential in some cases does not allow the determination of the value of the exchange current density.
Intracluster Proton‐Transfer between Methylsubstituted Benzene Cations and Polar Solvent Molecules Studied by Resonant Two‐Photon Ionization
Authors: Brutschy B. , Janes C. , Eggert J. 
Published: March 2014

AbstractIntracluster proton‐transfer was observed for mixed clusters of toluene and p‐xylene with polar solvent molecules (NH3, CH3OH, D2O) after resonant two‐photon ionization of the aromatic moiety. The transfer is deduced from the appearance of protonated solvent clusters, showing the R2PI spectra of their mixed cluster precursors. This process, observable only in combination with subsequent dissociation, is cluster size dependent. The minimum number of solvent molecules necessary for a transfer to take place depends on the solvent's proton solvation energy.
A Gasphase Kinetic Investigation of the System F + HNO3 and the Determination of Absolute Rate Constants for the Reaction of the NO3 Radical with CH3SH, 2‐Methylpropene, 1,3‐Butadiene and 2,3‐Dimethyl‐2‐Butene
Authors: Rahman M. M. , Becker E. , Benter Th. , Schindler R. N. 
Published: March 2014

AbstractThe reaction of HNO3 with atomic fluorine (1) has been studied in a discharge‐flow system at 298 K. Mass spectrometric detection with single ion counting was employed. The rate constant for the primary reaction (1) at 298 K. has been determined from the rate of HF and NO, formation under conditions [HNO3] ≫ [F]0 and the rate of HNO3‐removal under conditions [F] ≫ [HNO3]0

From the patterns of growth and decay of the primary product NO3 and the secondary product FO under various ratios of the initial concentrations of the reactants, the rate constants of the following secondary reactions have been determined:

Further, the rate constants for the reactions of NO3 with CH3SH, 2‐methylpropene, 1,3‐butadiene and 2,3‐dimethyl‐2‐butene at 298 K have been determined by introducing these reactants into the flow system and measuring their consumption under pseudo‐first‐order conditions. The values of the rate constants obtained are 7.7 ± 0.5, 3.3 ± 0.5, 1.7 ± 0.3 and 384 ± 38 in units of 10−13 cm5 s−1 respectively. A comparison is made between the values determined in this work and those reported in the literature.
Ion Relaxation in Aqueous Polyethyleneoxide Solutions Studied by Nuclear Magnetic Relaxation
Authors: Breen J. , Huis L. , De Bleijser J , Leyte J. C. 
Published: March 2014

AbstractThe nuclear magnetic relaxation rates of some ions are studied in aqueous PEO solutions. The relative molal increase of the ion relaxation is obtained for a number of ions. In a limited range the DP‐dependence, salt concentration dependence and temperature dependence are investigated. The quadrupolar relaxation mechanism of ions provides a means to investigate the ion hydration complex. The enhancement of the ion relaxation rate by the presence of PEO is interpreted by an ion hydrationcomplex‐PEO interaction. Two dynamical models are evaluated. One of the models is able to explain the NMR results and does not contradict the results obtained from neutron diffraction experiments.