bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymers and Fibers from Vinylidenedicarbonitrile
Authors: Sprague B. S. , Greene H. E. , Reuter L. F. , Smith R. D. 
Published: December 2003

AbstractVinyldendicarbonitrile (Vinylidene cyanide) on free redical catalyzed copolymerization shows a much stronger tendency to form 1:1 alternating copolymers than acrylonitrile. While bulk poly(vinylidene cyanide) fails to crystallize, despite its molecular symmetry, several alternating copolymers are readily crystallizable, notably those containing butadiene, isoprene, isobutylene, or vinylidene chloride. Fibers have been prepared from a number of the higher melting copolymers and examined for physical properties. Fibers from the vinyl acetate and vinyl chloride copolymers show expectional elastic behavior both when dry and wet. The fiber from the vinylidene cyanide |vinyl acetate alternating copolymer (Darvan® nytril fiber) is only moderately oriented and is characterized by exceptional softness and excellent elastic recovery and resilience, both when dry and wet.
Pyrrolidone, Capryllactam and Laurolactam as new Monomers for Polyamide Fibers
Authors: Dachs K. , Schwartz E. 
Published: December 2003

AbstractThe industrial production of capryllactam (1‐azacyclononan‐2‐one) and of laurolactam (1‐azacyclotridecan‐2‐one) starts with cyclization of acetylene or butadeine to give cyclooctatetraene or cyclooctadiene, or cyclization of butadiene to give cyclododecatriene. Further steps are: oxidation of the cyclic hydrocarbon to the ketone, formation of the oxime, and rearrangement of the latter with sulfuric acid. Pyrrolidone can be prepared from acetylene and formaldehyde by way of butyrolactone. The behavior of the lactams during polycondensation is described and the properties of the resulting fibers are compared with those of the known polyamide fibers.
Attempts to Synthetize Tetramethylyclobutadiene
Authors: Criegee R. 
Published: December 2003

AbstractAttempts to prepare cyclobutadiene, which is primarily of theoretical interest, or one of its derivatives have so far led only to products structurally closely related to tetramethylcyclobutadiene. It has not been possible to prepare the compound itself nor to establish unequivocally that it occurs as a reaction intermediate.
Reactivity of Dichloro‐ and Trichloropyrimidyl Dyes and the Sensitivity of their Dyeings to Hydrolysis
Authors: Thumm O. , Benz J. 
Published: December 2003

AbstractSeveral examples are used to show that the reactivity of dichloro‐ and trichloropyrimidyl dyes and the sensitivity of their dyeings to hydrolysis are determined by the nature of the bridge unit between the chromophore and the reactive system. The tendency of the dyeings to hydrolyze in acid and, more particularly, in alkaline media increases with increasing reactivity of the dyes. In alkaline media, dyeings made with dyes containing oxygen bridges are cleaved mainly between the reactive system and the chromophore, while in dyeings made with dyes containing imino or methylimino bridges, the linkage between the reactive system and the cellulose is hydrolyzed.
Automatic Activity Measurements during the Separation of Radioactive Compounds by Thin‐Layer Chromatography
Authors: Schulze P.‐E. , Wenzel M. 
Published: December 2003

AbstractA method was developed for continuous automatic measurement of the radioactivity distribution of weak β‐emitters on open columns, for example, thin‐layer chromatograms. It may be used for analytical separations, as well as for preparative separations on a semi‐micro scale. During the measurements the substances are not contaminated by addition of other materials.
High‐temperature Chlorination of Amines and Acylamines
Authors: Holtschmidt H. 
Published: December 2003

AbstractHigh‐temperature chlorination of acyl derivatives of primary and secondary amines and of tertiary alkyl amines usually yields compounds containing either the imidochloride (monochloromethyleneamino) group or the dichloroisocyanide (dichloromethyleneamino) group . In many cases, yields in the range of 80 to 95% are obtaied. Several ring‐opening and ring‐closing reactions ocurring under the conditions of high‐temperature chlorination ae described.
Low‐Temperature Polymerization of Ethylene
Authors: Bestian H. , Clauss K. , Jensen H. , Prinz E. 
Published: December 2003

AbstractA two‐component organometallic catalyst of composition CH3TiCl3·CH3AlCl2 effects high‐speed polymerization of ethylene in the presence of chlorinated hydrocarbons at low temperatures. The catalyst does not undergo any alteration in the process. In contrast to the Ziegler catalysts, the titanium remains quadrivalent. Olefins of low‐molecular‐weight and with branched structures are produced. It proved possible to isolate the primary products of the polymerization at −50 to −100°C and to elucidate the mode of their formation from a knowledge of their structures. The findings are incompatible with either a cationic or anionic reaction mechanism. A novel type of mechanism is proposed, whereby the catalyst is supposed to have an ionic structure and molecular growth proceeds via π‐complex formation of the olefin with the titanium cation. The formation of ethylene/olefin copolymers is also discussed.
Organic Derivatives of Mica‐type Layer‐Silicates
Authors: Weiss Armin 
Published: December 2003

AbstractMica‐type layer‐silicates such as montmorillonite and vermiculite are capable of exchanging their cations for other (including organic) cations, just like the zeolites. These derivatives swell in a variety of liquids. This paper presents a survey of the structures of organic derivatives of mica‐type layer‐silicates and illustrates some possibilities for their industrial utilization.
(Halogenomethyl)pyridines and (Halogenomethyl)quinolines
Authors: Mathes W. , Schüly H. 
Published: December 2003

AbstractHitherto, 2‐ and 4‐trihalogenomethyl‐pyridines and ‐quinolines were the only compounds of this type readily assessible by direct halogenation with free halogen. The particularly important and highly reactive monohalogenomethyl compounds had to be prepared by roundabout means, except in special cases. In the present article, a method is described for direct monochlorination of 2‐methyl groups in heterocyclic bases on a technical scale. A reveiw is also given of the preparation and properties of (halogenomethyl) pyridines and (halogenomethyl)quinolines.
Gas Chromatographic Investigation of Racemization during Peptide Synthesis
Authors: Weygand F. , Prox A. , Schmidhammer L. , König W. 
Published: December 2003

AbstractIt is shown that the methyl esters of many diastereoisomeric N‐trifluoroacetyldipeptides can be separated by gas chromatography on Golay columns. This makes it possible for the first time to carry out accurate quantitative investigations of recemization occurring during peptide synthesis without resort to measurements of optical rotation or enzymatic cleavage, and witout having to isolate the peptides. Some well‐known methods of forming peptides were examined using the synthesis of the methyl ester of carbobenzoxy‐L‐valyl‐L‐valine as an example. The synthesis of the methyl ester of N‐trifluoroacetyl‐L‐valyl‐L‐valine was investigated as a model for the linking of peptides. The influence on racemization of numerous factors was determined. General conclusions could be drawn regarding peptide synthesis.
Preparative and Analytical Separation of Organic Compounds by Means of Chromatography on Polyamide
Authors: Endres Horst , Hörmann Helmut 
Published: December 2003

AbstractColumns of polyamide are well suited for chromatographic separation of numerous organic compounds, especially phenols, carboxylic acids, and aromatic nitro compounds. The method is also useful for isolating naturally occurring compounds on a preparative scale. The affinity of phenols for polyamides is due to the formation of hydrogen bonds to the peptide linkages of the polyamide, while aromatic nitro compounds are retained by means of free amino groups in the polymer. Quinones react irreversibly with the free amino groups of the polyamide. Quinones are not retained by acetylated polyamides although phenols are.
Mass Transport in Metallic Solids
Authors: Wever H. 
Published: December 2003

AbstractMass transport in a metallic solid requires that the lattice units exchange places. This is made possible by lattice defects. Also, a circular interchange has to be discussed. Driving forces cause the superposition of directional motion over the random motion of site exchange: When a chemical potential gradient exists, isothermal diffusion occurs; with an electrical potential gradient, electrolytic transport takes place; and with a temperature gradient, the effect is thermal diffusion. Both concentrational changes and dimensional changes may accompany these processes. From observation of these phenomena, the mechanism by which lattice particles change places can be deduced. In addition, it is possible to calculate characteristic data, such as migration energy, imaginary change, and heat of transportation.
Syntheses with s‐Triazine
Authors: Grundmann Ch. 
Published: December 2003

AbstractThe preparation and properties of s‐triazine are discussed. Nucleophilic reagents (even water) readily attack s‐triazine. Thus, open‐chain and heterocyclic compounds, e.g. formamidines, aminomethylene compounds, and triazole, pyridine, and pyrimidine deravatives are accessible from s‐triazine. With amidines and imido ethers substituted triazines are obtained (by trans‐triazination).The latter are formed via open‐chain intermediates.
Recent Investigations of Sulfur‐Nitrogen Compounds
Authors: Glemser O. 
Published: December 2003

AbstractThe preparation, properties, and structure of cyclic and acyclic sulfur‐nitrogen halides are discussed. In the cyclic compounds, SN rings with localised and delocalized π‐bonds occur. In acyclic halides, SN triple bonds are observed. Organic iminosulfur dihalides are discussed.
Kinetics and Mechanism of 1,3‐Dipolar Cycloadditions
Authors: Huisgen R. 
Published: December 2003

AbstractCriteria for the mechanism of 1,3‐dipolar cycloadditions which lead to 5‐membered rings are provided by the stereoselectivity observed with cis‐trans isomeric dipolarophiles, by the effect of solvent and substituents on the rate constants, by the activation parameters, and by orientation phenomena. A concerted addition, which can also be described in terms of molecular orbitals and in which the two new σ‐bonds are formed simultaneously, although not necessarily at equal rates, offers the best explanation of the experimental facts.
New Developments in the Chemistry of Polyphosphanes
Authors: Wiberg E. , Van Ghemen M. , Müller‐Schiedmayer G. 
Published: December 2003

AbstractWhile silicon and sulfur, which are situated to the left and to the right of phosphorus in the periodic table, from numerous chain and cyclic Si–Si and S–S‐compounds with varying numbers of members, until recently the polyphosphance chemistry has been limited to the two‐membered compounds diphosphane P2H4 and its derivatives. A number of results obtained in studies on polyphosphanes carried out in recent years will therefore be discussed, which, together with some more recent work by other authors, have led to an expansion of our knowledge of the prepration and properties of straight and branched‐chain as well as of cyclic and polycylic –P–P‐systems.
Some Aspects of the Chemistry of Organoselenium Compounds
Authors: Gosselck J. 
Published: December 2003

AbstractIn this article, the gradations in reactivity of organic oxygen, sulfur, and selenium compounds of equivalent structure (“isologues”) are reviewed. New or improved methods for the preparation of organoselenium compounds (especially saturated and unsaturated selenides) are described. The addtion of selenols onto acetylenic triple bonds cheifly to cisadducts.
Reactions of Olefins with the Titanium‐Carbon Bond
Authors: Bestian H. , Clauss K. 
Published: December 2003

AbstractAt low temperatures, ethylene and α‐olefins (Δ1‐olefins or 1‐alkenes) are rapidly converted into oligomrs by the two‐component organometallic catalyst CH3TiCl3·CH3AlCl2. To achieve smooth oligomerizations, aromatic or chlorinated hydrocarbons must be used as solvents. Although the activity of the titanium‐carbon bond is enhanced by the aluminum component of the catalyst, the aluminum and its methyl group do not participate in the reaction proper; the latter proceeds exclusively at the titanium‐carbon bond. The reaction will olefins can be used as an analytical method for the quantitative determination of the titanium‐carbon bond in admixture with the organoaluminum component. It is thus possible to follow the reaction leading to formation of the catalyst from titanium tertrachloride, as well as the processes occurring at the titanium‐carbon bond during the oligomerization of olefins. All the observations indicate that the catalyst possesses an ionic structure which is determined by the solvent. It is shown that the initial reaction step probably involves formation of a complex between the olefin and the alkyltitanium cation. The reaction scheme proposed is based on organometallic reactions which are characterized by carbanion and hydride transfers within the olefin‐cation complex. This mechanism, which is unusual for Ziegler catalysts, is due to the predominance of hydride transfers.
Proton Transfer, Acid‐Base Catalysis, and Enzymatic Hydrolysis. Part I: ELEMENTARY PROCESSES
Authors: Eigen M. 
Published: December 2003

AbstractThe proton occupies a special position as a promoter and mediator in chemical reactions occurring in solution. Many reactions in organic chemistry are catalysed by acids or bases; likewise, most enzymes contain active groups which promote acid‐base catalysis. To understand the reaction mechanisms involved, it is necessary to identify the elementary steps as well as their course in time. Systematic investigation of these elementary steps as well as their course in time. Systematic investigation of these elementary steps has become possible only with the development of new methods for studying very fast reactions. The present paper reviews the information obtained in this type of investigation. The result is a relatively complete picture of the elementary proton transfer mechanisms and a comprehensive description of the modes and laws of acid‐base and enzymatic catalysis.
Recent Developments in the Study of Lysozymes
Authors: Jollès P. 
Published: December 2003

AbstractLysozymes are widely distributed enzymes. They split the chemical skeleton of bacterial cell walls by hydrolysing the β (1 → 4) linkages between N‐acetylmuramic acid and N‐acetylglucosamine. the amino acid sequence of lysozyme from hen's egg‐white is known (129 amino acid residues). Lysozymes of different origins frequently differ in their primary structures although they exhibit qualitatively the same biological activity. The results obtained from investigations with lysozymes allow conclusions to be drawn regarding the chemical structure of the “backbone” of bacterial cell walls.
Reversibility of Energy Transformations in the Respiratory Chain
Authors: Klingenberg M. 
Published: December 2003

AbstractIn oxidative phosphorylation, the energy from the combustion of substrate hydrogen can be reversibly transformed into phosphate‐bond energy. This is the reason that oxidation‐reduction reactions in the respiratory chain can take place against the redox potential gradient if energy is supplied. The latter can come from ATP or directly from energy‐rich intermediates arising in the course of oxidative phosphorylation. – At the center of the present considerations is the postulate that there is an equilibrium prevailing in the respiratory chain that results from the reversibility of the reactions. At the same time this postulate provides a unifying approach to various phenomena related to the process of oxidative phosphorylation. Such an equilibrium may involve several components of the respiratory chain. Respiration thus corresponds to a dynamic equilibrium in the respiratory chain which deviates increasingly from the static equilibrium the greater the rate of respiration. Consequently, respiration can be considered as being regulated by the phosphorylation potential. – The stationary redox state of the components of the respiratory chain can be viewed as a simulataneous function of the phosphorylation potential and of the redox potential that effects both ends of the respiratory chain. The latter reacts to either extreme, i.e. to minimum or maximum differences in the redox potential, by forming characteristic patterns of the state of reduction of its components. Differences in redox potential amounting to as much as 280 mV can be over‐come by the phosphorylation potential for a single phosphorylative step. – The conditions for an equilibrium in the respiratory chain are also fulfilled from a kinetic viewpoint as the rates of the reverse reactions involving either electron or proton transfer are of the same order of magnitude as those of the forward reactions.
The Valence Tautomerism of Cyclooctatetraene
Authors: Huisgen R. , Mietzsch F. 
Published: December 2003

AbstractThe Diels‐Alder adducts of cyclooctatetraene and its derivatives are derived from the bicyclo[4,2,0]octane structure. A kinetic investigation shows that the Diels‐Alder addition of dienophiles to cyclooctatetraene and phenylcyclooctatetraene is preceded by a valence tautomerism equilibrium with bicyclo[4,2,0]octa‐2,4,7‐triene or its 7‐phenyl derivative.
Structure and Aromatic Character of Non‐benzenoid Cyclically Conjugated Systems
Authors: Hafner K. 
Published: December 2003

AbstractThe chemistry of aromatic compounds was originally confined to benzenoid hydrocarbons and their derivatives but has been enriched in the last decade by the discovery of numerous non‐benzenoid, cyclically conjugated systems that are more or less like benzene in their properties. This has necessitated a new conception of “aromatic character”. Theoretical and experimental studies have been applied to this problem. In this connection, several selected representatives of this class of compound are described, mostly from studies by the author's own group, and relationships between structure and “aromatic character” are indicated.
Three‐Membered Rings Containing Two Hetero‐Atoms
Authors: Schmitz Ernst 
Published: December 2003

AbstractSince their discovery five years ago, the diaziridines have become an extensive and easily accessible class of compounds. Hydrolysis of these compounds effects a simple synthesis of hydrazine, alkylhydrazines, and N,N′‐dialkylhydrazines. They are also powerful oxidizing agents. The rigidity of the three‐membered ring gives rise to a few stereoelectronic peculiarities. Investigations on the mechanism of formation of the three‐membered rings led to a new synthesis of oxaziranes and to discovery of the isomeric oximes with a three‐membered ring structure. The latter decompose readily to form diimide. Diazirines are cyclic isomers of the aliphatic diazo compounds and are surprisingly easy to obtain by dehydrogenation of suitable diaziridines; they are chemically much more stable than the linear isomers. Grignard reagents add onto the NN double bond without destruction of the three‐membered ring. Thermal decomposition yields carbenes.
Complexes of Tetradentate Ligands Containing Phosphorus and Arsenic
Authors: Venanzi L. M. 
Published: December 2003

AbstractThe effect of ligand shape on coordination numbers and geometry of coordination compounds has been studied using two tetradentate ligands containing phosphorus and arsenic. These tend to form five‐coordinate complexes with trigonal bipyramidal structure [Fe(II), Co(I), Co(II), Rh(I), Ni(II), Pd(II), Pt(II)], but can also form six‐coordinate complexes with octahedral structure [Fe(II), Ru(II), Os(II), Co(III), Rh(III), Pd(IV), Pt(IV)]. The magnetic properties and the stereochemistry of the complexes are explained by ligand field theory which predicts that, for metal ions with d6‐electronic configuration, a low overall field strength should favor the formation of five‐coordinate paramagnetic complexes while a high overall field strength should favor the formation of six‐coordinate diamagnetic complexes. – This work provides further indication that the tendency of polydentate ligands to use all the potential donor atoms is not as pronounced as is generally believed. This is shown by the isolation of chromium(III) complexes in which the tetradentate ligands are, in fact, acting as tridentate, and by the isolation of mercury(II) complexes where only two of the four donor atoms of the polydentate ligand are actually bonded to the central metal atom.
The Chemistry of New Heat‐Resistant Films and Fibers
Authors: Wallenberger F. T. 
Published: December 2003

AbstractThis survey is principally concerned with papers published since 1959 on hydrocarbon polymers, aliphatic poly(terephthalamide) fibers, poly(hydroxybenzoic acid) films, poly(oxadiazole) fibers, poly(benzimidazole) films, poly(phenyltriazole) films, poly(pyromellitimide) films, and fibers from cyclized poly(acrylonitrile). All these materials have extremely high melting points and satisfactory in‐use characteristics at high temperatures.
The Phenomenon of Phototropy
Authors: Luck W. , Sand H. 
Published: December 2003

AbstractA short survey of the present status of our knowledge in the field of “phototrophy” is presented. The laws which govern this phenomenon are described, taking parafuchsin and N,N′‐di‐methyl‐1,4‐diaminoanthraquinone as examples. Phototropy and thermotropy are related. The acceleration of the regression of phototropically induced states by irradiation with light is discussed in some detail. An understanding of phototropy promises insight into the mechanisms of photochemical reactions and into the prerequisites for the preparation of light‐fast dyes.
Electron Affinity of Organic Molecules
Authors: Briegleb G. 
Published: December 2003

AbstractThe formation of organic radical ions by direct electron exchange between a donor molecule D and an acceptor molecule A is becoming increasingly important, particularly with regard to reaction mechanisms involving intermediate radical ions. All redox processes also involve electron exchange. Finally, the knowledge of electron affinities and ionization energies of organic molecules is necessary for a quantitative theoretical interpretation of intermolecular resonance and of the semiconductor properties of crystalline organic compounds and molecular compounds.
Old and New Processes of Multiplicative Distribution (Liquid‐Liquid Extraction). A Comparison of the Methods of aterial Flow and the Mode of Action
Authors: Fischer Werner , Biesenberger K. , Heppner J. , Neitzel U. 
Published: December 2003

AbstractA new process is described for the separation of mixtures of materials by multiplicative distribution, which is characterized by repeated addition of the mixture throughout the whole process and by material exchange during the countercurrent flow of finite amounts of one, and infinitesimally small amounts of the other phase. The intrinsic features of the mode of action of the old distribution processes and the new one are developed, and their relationship to one another is discussed. In this connection, an attempt is made to clarify the confused situation in the terminology of this field by introducing clearer definitions. Reflux and “displacement distribution”, another new distribution process, are treated briefly in two final sections.