bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthese von Brassinosteroiden
Authors: Adam Günter , Marquardt Volker 
Published: September 2010

AbstractSince the discovery of brassinolide, the first member of a new class of steroidal plant growth regulators, the synthesis of such compounds has represented an area of tremendous activity. The synthetic pathways to the most important member brassinolide and other native brassinosteroids as well as to structural analogs including aza and thio compounds are reviewed. Besides the various methods for A/B ring functionalization especially the different principles for a stereoelective side‐chain construction, starting from 22‐aldehydes, Δ22‐sterols or pregnane derivatives as steroidal precursors, are discussed.
Methoden zur hierachischen Clusterung
Authors: Henrion André , Henrion René , Urban Petr , Henrion Günter 
Published: September 2010

AbstractThe methods of Pattern Recognition are a very powerful instrument for the arrangement and evaluation of inner relations of unknown subjects of investigation into groups of subjects which belong together as well as for the decision whether a priori unknown subjects belong to a priori known groups. Therefore these methods are useful for solving many chemical problems. After having published contributions about Principal Components, Non Linear Mapping and Non‐Hierarchical Clustering with CLUPOT here a complex BASIC‐program for the alternative application of the most important methods of hierarchical clustering like Single‐, Complete‐, Centroid‐, Average‐ (weighted and unweighted) Linkage, Ward's method and Flexible Strategy (according to Lance and Williams) is described which make it possible to choose the different distances (Euclid, Manhattan, Mahalanobis) and to find out the best approximation of method and subject of investigation. As a first example trace analytical results of different laboratories for different tungsten powders are compared.
Insertionsreaktionen mit Isocyanaten — Reaktionsmöglichkeiten, Kinetik, Mechanismen
Authors: Noack Rainer , Schwetlick Klaus 
Published: September 2010

AbstractThe insertion reactions of isocyanates into CN, CO, CS, SiN, SiO, SiS, SiP, PN, PO, PM, BC, BN, BO, BS, BHal, SnN, SnO, SnS and other MX bonds are reviewed. Rate constants are in the range of 10−6 to 103 M−1 s−1, often above 10 M−1 s−1. Reaction mechanisms freguently involve equilibria prior to the rate determining step. Cyclisations to N‐heterocycles, uretdiones and isocyanurates and formation of carbodiimides are observed as side‐reactions. Ring expansions open routes to macrocyclic compounds. Insertions are important in organometal catalysis of isocyanate reactions as well as in metal complex catalyzed syntheses and, therefore, in a number of industrial processes.
Thiocarbonsäureanhydride — eine neue Klasse von Thioacylierungsmitteln
Authors: Martin Arnim A. , Barnikow Günter 
Published: September 2010

AbstractThiocarboxylic anhydrides represent a new class of useful thioacylating reagents. For ten years they have increasingly been investigated whereas the application is limited because of their partly remarkable instability. The preparation is carried out by means of relatively simple reactions. From the beginning of our century first attempts to prepare thioanhydrides failed. Kato et al. first published the isolation and characterization of pure thiocarboxylic anhydrides in 1976.
Physikalisch‐chemische Verifikationsmöglichkeiten für ein C‐Waffen‐Verbot
Authors: Stöhr Ralf , Stock Thomas , Müller Konrad 
Published: September 2010

AbstractThe question of verification is one of the most intensively discussed problems for a chemical weapon convention at the Geneva Disarmament Conference. With the development and stockpiling of binary warfare agents in the USA the verification tasks reach a new dimension.Sampling methods and analytical techniques are discussed for an efficient verification system for field tests and laboratory applications. Physicochemical techniques, e.g. enzymatic analysis, High Performance Liquid Chromatography, Gas Chromatography and their couplings with Mass Spectrometers or Fourier Transform‐Infrared Spectrometers are preferential techniques for central laboratories.
Poly(phenylenvinylen); Entwicklung eines elektroaktiven Polymermaterials vom unschmelzbaren Pulver zum transparenten Film
Authors: Hörhold Hans‐Heinrich , Helbig Manfred , Raabe Dietrich , Opfermann Johannes , Scherf Ullrich , Stockmann Regina , Weiß Dieter 
Published: September 2010

AbstractThe development of PPV systems has moved from intractable powders to flexible films. This opens new uses as thin film insulation material, as photoconductive electrophotographic recording material, and as novel electrochemical electrode material for polymer batteries. Tractable films were readily achieved either by transformation of a soluble precursor polymer or by introduction of solubilizing phenyl substituents. Contrary to wide‐spread expectations PPV is not a metal‐like conductor, but rather a broad‐band gap photoconductor (Eg= 2,4 eV). However, it can be made highly conducting upon appropriate chemical or electrochemical treatment, thus forming several salt‐like redox stages (σ = 10−4to 103S/cm). The formation of coexisting polymeric ion radicals (polarons) and diions (bipolarons) is well understood in terms of the concept of chain segment redox reactions (ECS concept). More detailed studies of the phenyl substituent effect show that the electronic properties are not altered drastically, but are modified due to broadening the band gap up to 2,9 eV along with an increase of the oxidation potential. Furthermore, phenyl substitution increases the resistance to heat, and stabilizes the deeply coloured redox stages.
Struktur, Eigenschaften und Anwendungen von Heteropolyverbindungen
Authors: Lunk Hans‐Joachim , Schönherr Siegfried 
Published: September 2010

AbstractThe present paper tries to give a survey of the field of heteropolyanion compounds the first of which were described as early as 1826 by Berzelius and of heteropolycation compounds which were prepared only recently. There is an obvious similarity between these two classes of compounds although the heteropolyanions are formed of transition metals of subgroups 6 and 5 (Mo, W, V, Nb, Ta) while in the heteropolycations the main group metal aluminium functions as the polyatom.The introductory chapter presents a short historical survey; the following chapters describe synthetic methods, structural interrelationships and applications of these two classes of compounds. The coordination number of the heteroatom with respect to oxygen was chosen as the principle of classification of the heteropolyanions. This allows to show the close structural relations existing between anionic and cationic complexes.
AIBIIICVI2‐Halbleiter mit Chalcopyritstruktur
Authors: Kühn Günther , Neumann Hans 
Published: September 2010

AbstractThe ternary AIBIIICVI2chalcopyrite semiconductors are current of technological interest since they show promise for applications in such areas as solar cells and non‐linear optics. In this paper we give a survey about the crystal chemistry of this compounds including the structure of epitaxial layers and discuss some new results concerning their thermal properties. Furthermore the influence of the p‐d hybridization of the uppermost valence band on the band gap and the nature of the intrinsic defects in CuInSe2are considered.
Charakterisierung des σ‐Akzeptorverhaltens von modifizierten Polykieselsäuren
Authors: Spange Stefan , Hortschansky Peter , Ulbricht Antje , Heublein Günther 
Published: September 2010

AbstractThe acceptor properties of various modified poly silica acids as aerosil or suprasil have been investigated by means of complexation with Fe(phen)2(CN)2 in suspension of 1,2‐dichloroethane. U V‐measurements and the acceptor number (AN) of Gutmann fits a linear relation.The influence of water on the surface acceptor strength in comparison to the behaviour in volume is discussed. Chlorination by SOCl2 drastically elevates the acceptor strength. Ester formation or reaction with poly epoxides lowers the AN of the surface.
Analytische Technik zur Quecksilberspurenbestimmung
Authors: Streufert Belief 
Published: September 2010

AbstractThe determination of mercury will be more and more important for environmental protection. The topic of this paper is the investigation of traces of mercury in water solutions and solid matters. It is entered in advantages and dis‐advantages of analytical methods applied to determination of traces of mercury. The flameless AAS (cold vapor method) is described as the most advantageous analytical method for investigations of one in water solutions. The graphical solutions of measuring results is presented and advices about systematic errors are also given.
Aus der Geschichte der physikalischen Chemie an Berliner Hochschulen während der Zeit der Berliner Physik
Authors: Bartel Hans‐Georg 
Published: September 2010

AbstractThe history of physical chemistry in Berlin during the period from 1870 to 1933 is reviewed. The Landwirtschaftliche Hochschule as well as the University of Berlin are playing a main role. The activities of H. Landolt, H. Jahn, J. H. van't Hoff, W. Nernst and M. Bodenstein in research and in lectureship are highlighted. Their works concerning optical activity, constancy of masses during chemical reactions, electrochemistry, thermodynamics, chemical kinetics and others are linked to the development of chemistry and physics. Landolt's and Nernst's aims to organize science and their relationship to the Physikalisch‐Technische Reichsanstalt are described. During the period mentioned above the physical chemistry in Berlin was part of the so‐called Berliner Physik.
Über die Azo‐Hydrazon‐Tautomerie
Authors: Mustroph Heinz 
Published: September 2010

AbstractSince the azo‐hydrazone tautomerism was discovered, it has been the subject of much research and much heated debate. Only modern spectroscopic methods led to clear experimental evidences. Therefore, the first part of the review describes the spectroscopic methods (UV/VIS, IR, mass, NMR and X‐ray photoelectron spectra and crystal structure analysis) associated with a more detailed evaluation of the certainty of the results so obtained. It is shown that nuclear magnetic resonance (δH, δ13C, δ15N, δ14N, J15NH) is a generally applicable tool and it leads to the most reliable results. In the second part, a survey of the tautomerism of p‐hydroxyazo‐benzenes, phenylazonaphthols and the azocoupling products of pyrazolones and ß‐diketones is given. The effects of substituents, anellation and H‐bonding are summarized. The various assumptions, indications and evidences of tautomeric structures and solvent effects are discussed critically.
Über ternäre Komplexe des Eisen(III)‐Ions mit Aminopolycarbonsäuren und einigen Liganden
Authors: Koch Siegfried 
Published: September 2010

AbstractIn this paper is discussed the ternary complexation of iron(III) with aminopolycarboxylic acids (nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid) and some inorganic as well as organic ligands.The complicated equilibria in aqueous solution were investigated by spectrophotometric and in some cases by electrophoretic methods. It was found that the composition of the species is Fe: APC:L = 1:1:1. The reaction mechanism of these equilibria is suggested and the stability of ternary complexes is described. The measured optical properties (λmax, ϵmax) of the mixed ligand complexes are discussed and compared with the corresponding binary species.
Display‐Methoden bei der Mustererkennung
Authors: Henrion René , Henrion André , Henrion Günter 
Published: September 2010

AbstractIn addition to other methods of pattern recognition (for instance cluster analysis) display methods have much importance. They give the possibility of graphical representation of originally multidimensional data sets under different aspects. Some of the most important display methods like principal component analysis, linear discriminant display, nonlinear mapping and others are explained, compared with each other, discussed and illustrated in their relations. Data sets of analytical chemistry results are evaluated by BASIC programs for microcomputers and used for explanation of the possibilities and limits of the above mentioned methods.
Internationale und nationale Methoden der Verifikation regionaler und globaler Vereinbarungen zum Verbot chemischer Waffen
Authors: Lohs Karlheinz , Stock Thomas , Kläß Volker 
Published: September 2010

AbstractVerification is the key issue in the ongoing Genevea talks on a comprehensive ban of all typs of chemical weapons, including the precursors of the binary warfare agents. To solve the still open questions regional steps as well as global proposals are under discussion. There are national and international control systems, techniques and methods useable. Automatic monitoring from the civil chemical industry and also the safeguards experience of the IAEA in Vienna can be examples to promote the treaty. Finding a general acceptable solution is very urgent, because otherwise a new spiral in the chemical arms race will be irresistible.
Struktur und Reaktivität von alternierenden Maleinsäure‐Anhydrid‐Copolymeren
Authors: Rätzsch Manfred , Steinert Volker 
Published: September 2010

AbstractAlternating copolymers that contain maleic anhydride (MAn) as a component occur in two different stereochemical configurations which are differentiated by their reactivity. Model compounds, 2, 3‐dialkylsuccinic acids and their anhydrides, were investigated and it was demonstrated that there is a distinct difference between threo and erythro configurations in their chemical and physical behaviour. Both configurations also occur in the alternating copolymers.The relative reactivity of the anhydride group compared to other carbon acid derivates and the mechanism of reaction to catalized and uncatalized nucleophiles are discussed. The reaction results of model compounds and of alternating MAn‐copolymers to aromatic and aliphatic amins are presented. The cyclization reaction to corresponding imides is described, and their dependence from the amine basicity and from steric effects of amine and its copolymers, produced without and with catalyzer, is outlined.
Zur Wechselwirkung von Stickstoff und Sauerstoff mit Adsorptionszentren in Zeolithen
Authors: Oehme Wolfgang , Meiler Wolfgang , Lochmann Jens Rainer , Siegel Hans 
Published: September 2010

AbstractBy use of adsorption measurements and 15N nmr studies could be shown that the adsorption of nitrogen in zeolites of type A and X is strongly influenced by the cations. The interaction increases in the sequence Na+ < Ca2+ < Mg2+. Whereas the interaction with Na+ and Mg2+ leads to chemical shifts of −2,5 and −9,5 ppm, respectively, the adsorption of nitrogen in a cation free zeolite shows no influence on the chemical shift with reference to free gas. Ab initio and semiempirical calculations support the results of the experiments. By extention of these calculations to oxygen the preference of nitrogen could be proved.
Lipophile Kronenverbindungen — selektive Extraktionsmittel für Metallionen
Authors: Gloe Karsten , Mühl Peter , Beger Jörg 
Published: September 2010

AbstractDue to their pronounced complexing properties and selective solubilities lipophilic crown compounds can be used as effective extractants for metal ions. Structure modification of those compounds allows the directed influencing of complex‐forming tendency and extractability. In this review various aspects of extraction equilibria and the recent progress in the liquid‐liquid extraction of metal ions with crown compounds have been discussed. It is shown, that functionalized crown compounds give attractive possibilities in the winning, separation and concentration of metals. Especially promising are crown compounds with acid‐dissociable groups, because in this case a additional anion transfer during extraction of metal ions is not necessary. Further investigations in the field of synthesis and extraction of crown compounds can be expected with new fruitful and interesting results.
Lokalisierte versus delokalisierte Molekülorbitalbeschreibung Zusammenhänge — Strategien — Regeln
Authors: Soukup Rudolf Werner , Jameson Reginald F. 
Published: September 2010

AbstractHighly localized and extensively delocalized representations of the molecular wavefunction are equivalent. If simple Lewis octet structures are zero order approximations of the localized valence molecular orbitals, the conventional MOs can be easily predicted using group theory. Valence state ionisation potentials in connection with the Sanderson concept of homonuclear binding energies are the basis for estimations of the orbital energies. The significance of such estimations is proven in some examples.
Natriumwasserglaslösungen — Aufbau, Eigenschaften und Probleme
Authors: Hoebbel Dagobert , Ebert Roland 
Published: September 2010

AbstractThe paper gives a review of more modern results of the 29Si n.m.r., chromatographic methods, molybdate and dye adsorption methods regarding the structure and characterization of technically important sodium water glass‐(sodium silicate‐solutions) with molar ratio SiO2/Na2O = 3–3,5. There are described the influence of molar ratio, SiO2 concentration, condensation degree, impurities and thermal treatment on the structure and properties respectively of sodium water glass (NaWG) solutions. The results show that the complicate structure of NaWG solutions and their influenceability by temperature, impurities, molar ratio and SiO2 concentration and furthermore the lack of suitable methods are reasons for the present insufficient characterization of NaWG solutions. It is shown that a more complete characterization especially regarding the thermal history of NaWG solutions is possible by combination of the molybdate method with the dye adsorption method. There is a hint of the existence of a thermal equilibrium state, which is influenced not only by the silicate anion distribution but the association equilibrium exused by concentration and state of distribution of impurities.
Anwendung “künstlicher Intelligenz”in der Chemie;Computersimulationen von Struktur‐Eigenschafts‐Beziehungen
Authors: Adler Bernhard , Dobers Sven , Eitner Bernd , Felgner Lutz , Mertsching Gudrun , Sorkau Eduard 
Published: September 2010

AbstractThe proceedings of chemical structure descriptors for structure‐activity studies is proposed. These descriptors are based on the set of properties distributed in a topological space (molecular graph). It dominates perceptions of empirical descriptors or of autocorrelation descriptors from physical properties of atoms, for instance, of electronegativities, polarisations or volumes of chemical groups. The choice between these different methods is determined by the type of interactions of chemical compound with the receptor. By means of pattern recognition techniques you can make a classification of molecules on the base of the activity features. As well we obtaine fuzzy results with 75–95% probabilities only
Metallclusterverbindungen — Chemie und Bedeutung;Cluster mit isolierten Hauptgruppenelementatomen, große Metallcluster, Clusterfluxionalität
Authors: Walther Bernhard 
Published: September 2010

AbstractThis part of the review on metal cluster compounds deals with clusters containing isolated main group element atoms, with high nuclearity clusters and metal cluster fluxionality. It will be obvious that main group element atoms strongly influences the geometry, stability and reactivity of the clusters. High nuclearity clusters are of interest in there own due to the diversity of the structures adopted, but their intermediate position between molecules and the metallic state makes them a fascinating research object too. These both sites of the metal cluster chemistry as well as the frequently observed ligand and core fluxionality are related to the cluster metal and surface analogy.
Multivariate statistische Bewertung von Ringversuchsdaten
Authors: Henrion Günter , Henrion René , Dietrich Thomas , Heininger Peter 
Published: September 2010

AbstractAs an example for evaluation of results of intercalibration and for valuation of laboratories the determination of Cr, Ni, Cd, Cu, Pb, Zn by 14 laboratories with flame AAS has been taken. The elements have been determined in synthetical solutions similar to river and to waste water. For the calculations BASIC computer programs have been used. Results for the single elements are compared with results for the six elements together. For this purpose displays of principal components, of nonlinear mapping and of linear discriminance analysis are suitable. NLM has some advantages, LDA important draw backs.
Ordungsfaktoren in der organischen Synthese Mustererkennung als Methode der Faktorenanalyse
Authors: Heimbach Paul , Bartik Tamas , Boese Roland , Schenkluhn Hartmut , Szczendzina Georg , Zeppenfeld Eva 
Published: September 2010

AbstractIn linear‐free‐energy relations and free‐energy relations substituents are characterized by so‐called “electronic” parameters, σ1‐parameters of substituents e. g. show direct correlations to Tolman's X1‐parameters or our P‐parameters. But by systematic variations at tetrahedral phosphorus we found a further set of Δ‐parameters, by which representative substituents like ‐OMe/‐SMe and ‐CMe3/‐SiMe3 with nearly identical Xi‐ or P‐parameters may be further characterized. The opposite influence of substituents on chemical behaviour is determined by the +/−sign of Δ‐parameters. By the signs of P‐and Δ‐parameters with triphenylphosphane as standard alternative order factors like DO/ACC, EVEN/ODD and S/AS may be identified. Compensation phenomena by selforganisation alone make LFE‐relations applicable. The importance of pattern recognition and consideration of absolute and relative control make general order control in chemical systems understandable (see next review).
Probleme toxikologischer Risikobeurteilung von Chemikalien
Authors: Pankow Dieter 
Published: September 2010

AbstractProblems and difficulties in assessment of the toxicological risk of chemicals are reviewed. Evaluation is possible by means of acute and chronic toxicity studies including testing of carcinogenicity, mutagenicity, teratogenicity, behaviour, immune reactivity, and reproduction. The task of the industrial toxicologist is to establish dose‐effect relationships in order to set toxicity thresholds. Threshold limits are based on simple theory: Organism can tolerate some dosages of any chemical without adverse effect and conversely, almost any substance can cause adverse effects if sufficiently high dosages are given. Very toxic chemicals can be defined promptly, but to prove that a less‐obviously toxic substance could never do anything, to anybody, any time, is impossible. To minimize the residual risk safety factors for establishment of threshold limit values were used. Some economic aspects of the risk assessment of chemicals are discussed.