bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoformation of “Z” (cis) Isomers in Diaryl‐ and Triaryl‐ Azomethines, Part II.1 Electronic and NMR Spectra of Methyl Derivatives of Benzylideneaniline (C6H5—CH=N—C6H5)
Authors: Maeda Koko , Fischer Ernst 
Published: November 2013

AbstractUV irradiation of benzylideneaniline, A, and its methyl derivatives B–E in aliphatic hydrocarbon solvents or CH2Cl2 results in extensive conversion into the corresponding “Z” (cis) isomers. The process is reversible both photochemically and thermally, and no pronounced side reactions were observed. At temperatures below about — 70° the Z modifications are thermally stable and their electronic and NMR spectra were measured by static methods. The extent of photoisomerization was estimated by means of the NMR spectra. The changes in electronic and NMR spectra resulting from the E → Z conversion were compared with those observed in the corresponding derivatives of stilbene and azobenzene. Photosensitized Z ← E at below — 70° was observed with biacetyl, but not with dye sensitizers having triplet energies below about 50 kcal · mol−1. Quantum yields for the direct photoisomerization in both directions were calculated, and are in the range of 0.1—0.6. As distinct from stilbenes and azobenzene derivatives, no appreciable temperature dependence of these yields was found, in the range — 70° to – 180°.
Photoreactions of Aromatic Compounds. XXXVII.1 Photosubstitution Reactions of Nitronaphthalene Derivatives
Authors: Lammers J. G. , Cornelisse J. 
Published: November 2013

AbstractA systematic investigation was made of the photochemical properties of 12 fluoronitronaphthalenes and some methoxynitronaphthalenes in the presence of hydroxide ions, methoxide ions and methylamine. Results show that photosubstitution of fluorine in fluoronitronaphthalenes by methoxide or hydroxide must be a consequence of the activating effect of the nitro group. This effect is also clearly present when the nitro group and the fluorine atom are in different rings.
Photoreactions of Aromatic Compounds. XXXVIII.1 Kinetics of the Photohydrolysis and Photoamination of 1‐Fluoro‐3‐nitronaphthalene, 1‐Fluoro‐6‐nitronaphthalene and 1‐Methoxy‐3‐nitronaphthalene
Authors: Lammers J. G. , Tamminga J. J. , Cornelisse J. , Havinga E. 
Published: November 2013

AbstractNucleophilic photosubstitution reactions of some naphthalene derivatives have been studied in order to establish new data on rate constants and other quantitative aspects of nucleophilic aromatic photosubstitution reactions. Results show that the photoreactions of the meta substituted fluoronitro‐ and methoxynitronaphthalenes with hydroxide ion and methylamine are SN2 (3Ar*) processes. In addition, it is shown that the lifetimes of the excited species in aromatic photosubstitution may be a decisive factor in determining the nature and the quantum yield of the reaction at moderate and low nucleophile concentration.
Topochemistry. Part XXXIX. The Solid‐state Photochemistry of some 2′‐Nitrochalcones
Authors: Jungk Axel E. , Luwisch Moshe , Pinchas Shraga , Schmidt Gerhard M. J. 
Published: November 2013

AbstractIt is shown that the specific pathway of a complex photochemical reaction in the solid state is governed by the molecular conformation and its retention, and by the molecular packing. 2′‐Nitrochalcone and those of its derivatives which are isomorphous with it display the s‐trans conformation in the solid state and yield indigos upon irradiation. However, this conformation is not sufficient to ensure photoreactivity: thus the s‐trans‐4‐bromo‐derivative does not yield indigo. The same derivative in the s‐cis conformation (in a second crystal form) has a crystal structure similar to that of the parent compound, and also does not yield indigo.
Thermodynamics of Power and Dissipation
Authors: Kafri O. , Levine R. D. 
Published: November 2013

AbstractCan one provide a thermodynamic theory for processes which occur with finite rates? We discuss a possible approach based on expressing the first and second laws as rate equations. The result is a first law formulated in terms of power and a second law in terms of rate of energy dissipation. We argue that such an approach introduces a distinction between passive systems which are devoid of memory and cannot store energy and systems with a facility of recall (e.g. a coiled spring). The second possibility, that of systems capable of recall, allows for short term deviations from the overall restrictions imposed by the second law, illustrating the maxim that knowledge is power.
Oxyfluoro Compounds of Bromine
Authors: Gillespie Ronald J. , Spekkens Paul H. 
Published: November 2013

AbstractRecent research on oxyfluorides of bromine is reviewed. This work is the first on the subject since 1963 when BrO2F was the only known oxyfluoride of bromine. Since then a number of other oxyfluoro compounds have been prepared, and a considerable amount of information on the structure and properties of all these compounds including additional information on BrO2F has been obtained. This review attempts to summarize all the data reported up to mid‐1977.
Fluorohalogenates: Preparation, Properties and Structure
Authors: Shamir Jacob 
Published: November 2013

AbstractRecent advances in the field of fluorohalogenate chemistry are reviewed. Areas considered include their preparation, properties and structure. It is concluded that while many of the expected anions formed by the various halogen fluorides can be isolated and identified, full understanding of their structures is hindered by their extremely reactive properties and the fact that their existence is mostly limited to the solid state.
Reactions of Organic Compounds with Xenon Fluorides
Authors: Filler Robert 
Published: November 2013

AbstractXenon fluorides, especially XeF2 and the intercalates of XeF4 and XeF6 in graphite, react with a broad range of aromatic compounds to provide a convenient direct route to fluoroaromatic compounds, many of which are otherwise difficult to prepare. Some of the products are of medicinal and biological interest. Highly colored radical cations are generated in the reactions by one‐electron oxidation. XeF2 also serves as a useful source of fluorine by reacting readily with carbon‐carbon double and triple bonds to yield difluoro‐ and tetrafluoro‐ addition products, as well as products resulting from rearrangements (especially in the case of norbornene).
Photochemistry of Fluorosubstituted Aromatic and Heteroaromatic Molecules
Authors: Zupan Marko , Šket Boris 
Published: November 2013

AbstractThe photochemistry of fluoro‐substituted aromatic and heteroaromatic molecules is reviewed. Investigations in this field of organic fluorine chemistry are summarized and some recent observations are presented. It is concluded that the fluorine atom is a convenient substituent for the elucidation of the reaction pathways of photochemical transformations of aromatic and heteroaromatic molecules.
Spirophosphoranes Containing the Perfluoropinacolyl Ring System
Authors: Röschenthaler Gerd‐Volker , Sauerbrey Karl , Schmutzler Reinhard 
Published: November 2013

AbstractA series of spirophosphoranes, [C6H4O2][OC(CF3)2C(CF3)2O]‐PR (R = F, Me, Bu1, Ph, and OMe) containing the catechol and perfluoropinacolyl ring system have been prepared. Characterization was by NMR and IR spectroscopy, mass spectrometry, and by elemental analysis. In some cases temperature dependent effects were observed in the 19F‐NMR spectra; the findings are rationalized in terms of a “high‐energy” ligand exchange process. Hydrolysis of the phosphorane with R = F may proceed along two different pathways, with formation of phosphoryl compounds.
The Influence of Fluorine Substitution on the Aromaticity of Carbocyclic Systems
Authors: Hess B. A. , Schaad L. J. 
Published: November 2013

AbstractHückel integral parameters were evaluated for F and Cl by fitting calculated to observed heats of atomization. With these, empirical C‐F and C‐Cl bond energy terms were obtained from Hückel calculations on a set of 34 halogen‐substituted acyclics. The effect of fluorine substitution on the resonance energy per π electron (REPE) of cyclic compounds was then examined. Both F and Cl were found to act as electron donors in affecting REPE with F being the stronger.
Field Ionization Mass Spectrometry. II. FD Spectra of Nucleotides — Analysis of Methylation Products of Dinucleoside Phosphates
Authors: Linscheid M. , Feistner G. , Budzikiewicz H. 
Published: November 2013

AbstractThe analysis of reaction products in methylation of four dinucleoside monophosphates (ApA, UpU, ApU, UpA) by FDMS is reported. Both the relative amounts of the various methylation products and the sites of methylation could be determined, the latter from the fragmentation patterns. The results are explained by the different reaction rates of the nucleoside moieties.
The Diurnal Rhythms in Plasma Glycine Pool Sizes and Turnover Rates: 15N‐Glycine Single Dose Experiments Employing Gas Chromatographic — Mass Spectrometric Analysis
Authors: Lapidot A. , Nissim I. , Irving C. S. 
Published: November 2013

AbstractGas liquid chromatography–mass spectrometry of trifluoroacetyl n‐butyl ester derivatives of plasma amino acids has been used to determine directly the 15N‐enrichment of plasma glycine in rabbits, following the intravenous administration of a single dose of 15N‐glycine. The isotope enrichment time decay curves of plasma glycine were linear over the course of the measurements (5–45 min). Glycine pool sizes and turnover rate constants were obtained from the intercepts and slopes of non weighted least‐squares lines, describing the isotope enrichment time decay curve. In fed animals, glycine pool sizes showed only modest variations over a 24 h period, while glycine turnover rate constants showed a statistically significant daily variation with a minimum at 10 PM. In fasted animals, the glycine pool sizes decreased and turnover rate constants increased with the duration of the fast. The turnover rate constants appeared to represent the utilization of glycine, as an energy or nitrogen source in the liver, rather than uptake of glycine into the free amino acid pool of muscle. These data indicate that physiologically significant variations in amino acid dynamics can be obtained from single dose tracer experiments, when GC‐MS is used to determine directly the isotope enrichments of plasma amino acids.
Analysis of Human Vaginal Secretions by Gas Chromatography–Mass Spectrometry
Authors: Preti George , Huggins George R. , Bares Jana 
Published: November 2013

AbstractVaginal secretions from 14 ovulating females were analyzed by gas chromatography (GC) and gas chromatography‐mass spectrometry (GC–MS) during 50 ovulatory cycles. The day of ovulation was documented in each case by charting of basal body temperature and/or determining hormonal profiles for estrogens, progesterone and luteinizing hormone. The secretions were found to contain a complex mixture of acids, alcohols and aromatic compounds. Two distinct types of vaginal environment were found with six subjects displaying large amounts of C2–C5 aliphatic acids in secretions and the remaining showing only acetic acid by GC–MS analysis. Predominant concentrations of these acids occur both at midcycle and in the luteal phase of the menstrual cycle. Lactic acid and urea were present in the secretions of all subjects and underwent cyclic variations in concentration with maxima occurring around midcycle. The effect of sexual arousal on the organic compounds in the secretions is also discussed.
13C‐Kinetic Isotope Effects in Photosynthetic Carboxylation Reactions and δ13C‐Values of Plant Material
Authors: Schmidt H.‐L. , Winkler F. J. , Latzko E. , Wirth E. 
Published: November 2013

AbstractThe influence of different parameters on δ13C‐values in plants in vivo and on the 13C‐isotope effect of the carboxylation reactions in vitro were examined using isotope ratio mass spectrometry.
Solvent Caused Quaternization as a Possible Source of Error in the Mass Spectral Quantitation of Tertiary Amines. I. Methylene Chloride Quaternization
Authors: Vincze Adam , Gefen Leon 
Published: November 2013

AbstractBasic tertiary amines such as atropine, derivatives of N‐methylpiperidine and quinuclidine, tend to quaternize in methylene chloride at room temperature. The quaternary ammonium salts formed undergo various dequaternization reactions in the heated direct inlet probe of the mass spectrometer, giving rise to volatile tertiary amines — different from the starting material and usually having higher molecular weights. Recorded spectra of such samples are a superposition of those of the various tertiary amines constituting the mixture. If just a few relevant and abundant ions in the mass spectrum of the original tertiary amine are monitored, as in quantitative fragmentography, rather low results might be obtained. Moreover, the operator may be quite unaware of the fact that he is measuring only part of the sample.
(Polystyrylbipyridine)palladium(0): Heterogeneous Catalyst for the Mild Hydrogenation of Dienes to Monoenes
Authors: Card Roger J. , Neckers Douglas C. 
Published: November 2013

Abstract(Polystyrylbipyridine)palladium(0) is an active catalyst for the selective hydrogenation of dienes to monoenes under mild conditions. Swelling solvents, such as tetrahydrofuran or benzene, are useable under 1 atm hydrogen at 25°C. The hydrogenation of linear isomers of hexadienes results in the formation of 1‐, 2‐ and 3‐hexene in each case. The hydrogenation occurs at the same rate for each of the hexadienes and < 1% hexane is observed until after consumption of the first equivalent of hydrogen. Cyclohexadiene undergoes hydrogen transfer to form cyclohexene and benzene. The chemistry observed is distinct from that observed in Bailar's use of (℗‐Ph‐CH‐2P(Ph2)2PdCl2as a hydrogenation catalyst.
The Three Phase Test: Intramolecular Nucleophilic Catalysis
Authors: Rebek Julius , Horton Joseph A. , Brown David 
Published: November 2013

AbstractAn unambiguous method for the detection of reaction in intramolecular nucleophilic catalysis intermediates is described. The three phase test involves generation of the intermediate from an insoluble, polymer‐bound precursor and its trapping by a second solid phase suspended in the same solution. The hydrolysis of monoesters of phthalic acid and of certain substituted phenyl esters is discussed.
Molecular Models for Solvent Structure at Polarizable Interfaces
Authors: Fawcett W. R. 
Published: November 2013

AbstractMolecular models developed to account for the dielectric properties of the polarizable metal/solution interface are reviewed. Experimental data obtained for both aqueous and non‐aqueous systems in the absence of specific adsorption are examined within the context of these models. It is concluded that a relatively simple model can describe the properties of the inner layer in aprotic solvents where intermolecular forces can be described on the basis of permanent and induced dipole—dipole interactions.
Raman Scattering from Adsorbed Molecules in Electrochemical Systems
Authors: Efrima S. , Metiu H. 
Published: November 2013

AbstractThe classical theory of Raman scattering from adsorbed molecules on solid surfaces is outlined, and modifications aimed at discussing electrochemical systems are presented. We propose a mechanism for intensity enhancement and compute the polarization and the angular distribution of the scattered radiation. It is shown that for some limiting cases the position of the molecule with respect to the surface may be inferred from experiments.
Accuracy of Determining Electrode Properties from Impedance Measurements
Authors: Despić Aleksandar R. , Jović Vladimir D. , Djorović Mihajlo V. 
Published: November 2013

AbstractAn attempt is made to estimate the accuracy which can be achieved in the evaluation of parameters of an electrode with an activation controlled electrochemical process from measurements of electrode impedance. Ferrous/ferric couple at platinum in perchloric acid was taken as a model system and the impedance components have been measured as functions of frequency at different concentrations. Double layer capacitance, CDL, faradaic resistance, θ, and the ohmic resistance of the cell R, have been identified from the characteristic functions, and the indeterminacies in their values evaluated from the probable errors of measurements. The problem of indeterminacy was generalized and regions in the CDL – θ – R space were defined outside which those parameters cannot be determined within present limits of accuracy.
Solid Electrolyte Interphase (SEI) Electrodes. Part 1. The Kinetics of Lithium in LiAlCl4‐SOCl2
Authors: Peled E. , Yamin H. 
Published: November 2013

AbstractThe lithium electrode is always covered by a film of lithium chloride which acts as solid electrolyte interphase (SEI). Macropolarization curves indicate that the Tafel slope is greater than 3 V for electrodes having SEI thicker than 400 Å. This confirms that the rds for the deposition‐dissolution process is the migration of lithium cations through the SEI. Increasing the electrolyte concentration increases the interfacial capacitance and decreases the resistivity of the SEI. This is explained in terms of the effect of LiAlCl4 concentration on the concentration of the lattice defects. The effect of the concentration of the electrolyte on the resistivity of the SEI decreases as the thickness of the SEI is increased. The growth rate of the SEI increases as the concentration of the electrolyte is increased.
Electrocatalysis on Surfaces Modified by Foreign Metal Adatoms
Authors: Adžić Radoslav R. 
Published: November 2013

AbstractAn approach to the problem of electrocatalysis, which consists of modification of electrode surfaces by foreign metal adatoms, is presented. The paper reviews the work done in the author's lab on the effects of foreign metal adatoms, formed by underpotential deposition, on kinetics of several electrode reactions. Catalytic effects have been illustrated on examples of oxidation of some organic molecules, oxygen reduction, and electrodeposition of metals. The inhibition has been found with hydrogen evolution on noble metals. Small catalytic and inhibitory effects have been observed with redox reactions. The effects of foreign adatoms on the surface properties of electrode catalyst and the origins of catalytic and inhibitory effects have been analysed. The use of such adatoms as a probe in investigation of the mechanism of electrode reactions is discussed.
Biomimetic Chemistry in Oriented Systems
Authors: Breslow Ronald 
Published: November 2013

AbstractBiomimetic chemistry is the field which attempts to imitate the accelerations and selectivities characteristic of enzyme‐catalyzed reactions. Enzyme chemistry is not slavishly mimicked in detail, but instead furnishes an intellectual stimulus to the design of novel catalysts and reagents. Work in this field at Columbia University is reviewed in the area of selective steroid transformations, reactions of flexible chains (in solution, micelle, and bilayer), and cyclodextrin lock and key chemistry inspired by chymotrypsin and by ribonuclease. Careful attention to geometrical factors leads to good mimics of the rates and selectivities of some enzymes.
Polymerization of Oriented Monomers. IV. Polymerization ofp‐Acryloyloxybenzylidene‐p‐butylaniline within a Liquid Crystalline Phase
Authors: Paleos C. M. , Voliotis S. 
Published: November 2013

AbstractThe effect of organization of a liquid crystalline monomer polymerized within a mesomorphic phase on its polymer morphology has been investigated. Specifically,p‐acryloyloxybenzylidene‐p‐butylaniline has been polymerized in the mesomorphic phase, which is obtained by melting a mixture of this monomer withp‐propanoyloxybenzylidene‐p‐butylaniline. Destruction of the liquid crystalline phase was avoided during polymerization by employing a monomer to solvent molar ratio equal to 1:3. In addition, the same monomer was polymerized in the isotropic melt of the same mixture. Polymers derived from both modes of polymerization were characterized by X‐ray diffraction and exhibited the same degree of crystallinity (about 70%). It is therefore concluded that monomer orientation does not affect polymer crystallinity and also that crystallinity originates from the strong interaction of polymer side groups or alternatively from the intrinsic tendency of polymers to organize.
Quasi‐Crystals
Authors: Krongauz V. A. 
Published: November 2013

AbstractIrradiation of solutions of photochromic spiropyrans in nonpolar solvents initiates a succession of spontaneous chemical and physical transformations, resulting in the appearance of colloidal spherical particles, globules, of very complex structure. They are composed of highly dipolar crystalline nuclei surrounded by amorphous envelopes. Due to their large permanent dipoles the globules are aligned in linear beaded structures in a constant electric field. Macroscopically these structures look like colored threads, extending along the electric lines of force. The globules and threads reveal properties associated both with crystals (optical and electric anisotropy, discrete X‐ray diffraction) and with amorphous materials (droplike form, fluidity). The globules grow stepwise, resulting in the appearance of several generations of threads with discrete increasing sizes of globules. The quasi‐crystalline globules mimic the organization of biomembranes.
Dipolar Micelles. 9. The Mechanism of Hydrolysis of Cationic Long Chained Benzoate Esters in Choline and Homocholine‐type Micelles
Authors: Pillersdorf A. , Katzhendler J. 
Published: November 2013

AbstractAn investigation was carried out on the hydrolytic reactions of the para‐substituted long chain esters N‐decyl‐N, N‐dimethyl‐N‐(2‐benzoyloxyethyl) ammonium bromide (CBE), N‐decyl‐N, N‐dimethyl‐N‐(3‐benzoyloxypropyl) ammonium bromide (HCBE) and decyl benzoates (DBE) in the cholinium type detergent N‐decyl‐N, N‐dimethyl‐N‐(2‐hydroxyethyl) ammonium bromide (I), and in the homocholinium type detergent, N‐decyl‐N, N‐dimethyl‐N(3‐hydroxypropyl) ammonium bromide (II). The first order rate constants (kc) of the trans‐benzoylation stage for HCBE in micelle I, CBE in micelle II and DBE in micelles I and II as catalysts were determined. The second order rate constants (k'OH) for the alkaline hydrolysis of these esters, were also evaluated. The results showed that the partition ratio (k−n/ko) of the tetrahedral intermediate formed during the reaction of I + HCBE, to the reactants and products, is relatively small when compared to the known values for oxygen esters in non‐micellar media. This phenomenon is discussed in terms of: (a) the stabilization of the anionic transition state by the positively charged micellar surface; (b) the electrophilic assistance to the expulsion of the leaving group; and (c) the favourable entropy of the substrate‐micelle intracomplex‐formation. Substituent effects on the rates (kc, k'OH) of CBE, HCBE and DBE were analyzed using the Hammett equation. When compared to the ρ values displayed in aqueous solution, the increased ρ values observed in micellar and dioxane‐water systems indicate that the hydrolytic reactions of HCBE and CBE in micelles proceed close to the less polar surface area. This requires a folded conformation of the head groups of the above mentioned esters. The low effectiveness of the hydroxylic micelles (I, II) in the hydrolysis of esters is also discussed.