bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adiabatic Photoreactions of Organic Molecules
Authors: Turro Nicholas J. , McVey Jeffrey , Ramamurthy V. , Lechtken Peter 
Published: December 2003

AbstractAn adiabatic photoreaction is a chemical process that occurs entirely on a single excited electronic energy surface. As a rule, most photoreactions of organic molecules start on an excited electronic surface but “jump” to a lower surface somewhere along the reaction coordinate. There are, however, exceptions to this general rule. For example, photoreactions involving small structural changes and minor alterations in covalent bonding (e.g., proton transfer and complex formation) are commonly found to occur adiabatically. The purpose of this review is to survey examples of more complicated adiabatic photoreactions such as fragmentation, electrocyclic rearrangements, and geometrical isomerizations. The concepts employed are presented in an introductory discussion.
Raw Material‐Polymer Interrelationships — Today and Tomorrow
Authors: Weissermel Klaus 
Published: December 2003

AbstractAgainst the background of increasing demand and limited availability of fossil, non‐regenerative fuel reserves and resources, ways are indicated of ensuring future supplies of raw materials and energy. The ambivalence of petroleum, natural gas, and coal in the energy and chemical sectors is demonstrated and opportunities for the gradual separation of their dual function are indicated. Taking into account the time factor, the necessary restructuring processes are analyzed critically with respect to their impact on the raw material–polymer relationship.
Coupling of Solvolysis and CC Linkage: A Promising Synthetic Route to Functionalized Carboxylic Acids, Aldehydes, and Ketones
Authors: Bott Kaspar 
Published: December 2003

AbstractNumerous additions of carbocations to chloroolefins or acetylenes can be coupled with a solvolysis step when performed in a suitable acid; the products are variously substituted carboxylic acids, aldehydes, and ketones. Factors determining the success of these syntheses are the stability of the intermediate carbocations and suppression of the competing addition of protons to the unsaturated reaction component. Under the conditions of the Tscherniac‐Einhorn reaction, amidomethylation of chloroolefins and acetylenes, i.e. the introduction of acylaminomethyl groups, is shown not to involve a trigonal α‐chloro carbocation or a linear vinyl cation, but instead to proceed via a cyclic oxazinium ion intermediate.
Synthesis of Intermediates by Rhodium‐Catalyzed Hydroformylation
Authors: Siegel Hardo , Himmele Walter 
Published: December 2003

AbstractThe reaction of olefins with carbon monoxide and hydrogen to give aldehydes is referred to as hydroformylation (oxo reaction). As catalyst for this reaction rhodium is about three to four orders of magnitude more active than the more commonly employed cobalt. With special rhodium compounds, e.g. di‐ν‐chlorobis(ν‐1,5‐cyclooctadiene)dirhodium [RhCl(C8H12)]2, in the presence of chiral phosphanes, even asymmetric hydroformylations can be achieved; however, the enantiomeric purity of the products (20–30%) is not high enough for industrial‐scale syntheses.
Computer Simulation of the Kinetics of Complicated Gas Phase Reactions
Authors: Ebert Klaus H. , Ederer Hanns J. , Isbarn Gunther 
Published: December 2003

AbstractModern digital methods and powerful computers make it possible to simulate the time behavior of chemical reactions. These calculations can be performed on systems containing an almost unlimited number of elementary reactions. Generally, however, the reaction models used should contain only those elementary reactions which describe the bulk of the conversion. Such a reaction model may be obtained by reduction of the complete set of elementary reactions. Another possibility is analysis of the chemical system starting from conditions ensuring a simple chemistry, which is generally the case at low temperatures and low conversions. The reaction model may then be extended into the range of the reaction variables (temperature, time) of interest. Mathematical simulations may be helpful during the development of the reaction model, and sometimes even decisive. These methods were applied to the pyrolysis of ethylbenzene and n‐hexane, and to CO oxidation. They yield information on the reaction paths, the importance of particular elementary reactions, and reaction stability. Furthermore, quantitative data can be obtained concerning the influence of single elementary reactions on the product distribution. The sensitivity matrix shows, e.g., whether the determination of kinetic parameters of an elementary reaction from kinetic data of the overall reaction is possible in principle, and how high the accuracy of the rate constants should be for simulation of the reaction. Both results are important for modeling chemical reactions.
The Influence of Density and Temperature on the Properties of Pure Molten Salts
Authors: Tödheide Klaus 
Published: December 2003

AbstractMolten salts differ from most other types of liquids because of their high charge carrier density, which is responsible for a number of their extraordinary properties such as high ionic conductivity. Experimental and theoretical investigations during the past few years have provided information on the static and dynamic microscopic structures of this class of liquids and their relationship with the macroscopic properties. A consistent, albeit incomplete picture of the behavior of molten salts over wide ranges of temperature and density is now available including the transition from an insulator to an ionic conductor which a salt undergoes when it is compressed from vapor‐like to liquid‐like densities.
Pharmaceutical Chemistry Today—Changes, Problems, and Opportunities
Authors: König Horst 
Published: December 2003

AbstractDissatisfaction with empirical methods, high expectations of the public, poorly harmonized international regulations, and rising costs have induced pharmaceutical research to search for new approaches. As a consequence, the medicinal chemist's professional activity is in a state of change. His synthetic strategy is being increasingly influenced by the reasoning of molecular biology. Novel classes of biologically active compounds demand the development of new synthetic methods beyond the scope of modern preparative organic chemistry: enzymes and microorganisms, cell cultures, and genetic engineering are harnessed to supply highly complex structures. Major efforts are devoted to the development of reliable structure‐activity relationships to rationalize his work. Thus the field of medicinal chemistry stretches from physical and physical organic chemistry far into the realm of biosciences, and the interdisciplinary character of this research is rapidly increasing. The author endeavors to convey an impression of this complex subject with the aid of selected examples.
Protein Differentiation: Emergence of Novel Proteins during Evolution
Authors: Schulz Georg E. 
Published: December 2003

AbstractThe almost limitless number of proteins can be reduced to approximately 200 basic structures, i.e. geometries of polypeptide chains; these form, the set from which the tracable protein differentiation started. Protein differentiation begins with a gene duplication. One of the gene products is conserved since it must continue to fulfill the original function. The other gene product is conserved as soon as it has taken over a new function. Comparing amino acid sequences of equivalent proteins in two species yields the evolutionary distance between these species, which allows dating of their common ancestor (“molecular palaeontology”). These comparisons are now applied to the geometries of nonequivalent proteins, elucidating the pathways of protein differentiation.
Alkylsulfamoyl Chlorides as Key Units in the Synthesis of Novel Biologically Active Compounds for Crop Protection
Authors: Hamprecht Gerhard , König Karl‐Heinz , Stubenrauch Gerd 
Published: December 2003

AbstractDue to their bifunctional character, alkylsulfamoyl chlorides are versatile units for the synthesis of heterocycles, polar sulfamates, and sulfonamides. In the last decade, synthetic methods of general preparative use have been developed, by means of which amine hydrochlorides, isocyanates, aziridines or tertiary alcohols can be reacted with suitable sulfuric acid derivatives to give novel, variously substituted alkylsulfamoyl chlorides. These compounds can subsequently be converted either to previously unobtainable N‐alkoxyalkyl‐N‐alkylsulfamoyl chlorides or to novel heterocycles of the type 1H‐2,1,3‐benzothiadiazin‐4‐one‐2,2‐dioxide, 2H‐1,2,6‐thiadia‐zin‐3‐one‐1,1‐dioxide and 2H‐1,2,4,6‐thiatriazin‐5‐one‐1,1‐dioxide; these compounds are examples of interesting models which illustrate the relation between the structure and the action of the compound, and in some cases lead to highly selective, ecologically unobjectionable herbicides. On the other hand, the alkylsulfamoyl chlorides themselves can be N‐acylated to give further 3‐ to 5‐atom bifunctional synthesis units, with which novel heterocyclic syntheses can be carried out. Further uses of the alkylsulfamoyl chlorides include the preparation of biologically active sulfamates, and cycloaddition reactions of N‐sulfonylamines prepared in situ.
The Transition Metal‐Nitrogen Multiple Bond
Authors: Dehnicke Kurt , Strähle Joachim 
Published: December 2003

AbstractNumerous nitrido complexes of transition metals show very short metal‐nitrogen bond lengths, suggesting MN‐triple bonds. At present, compounds of this type are being intensively investigated. In particular the molybdenum complexes are considered as model substances for the study of at least an intermediate step of N2‐assimilation. This article contains a review of the structure and bonding, as well as syntheses and reactions of these complexes.
Phospha‐alkenes and Phospha‐alkynes, Genesis and Properties of the (p‐p)π‐Multiple Bond
Authors: Appel Rolf , Knoll Fritz , Ruppert Ingo 
Published: December 2003

AbstractJust as the octet rule had prevented the discovery of the inert‐gas compounds, the systematic search for phosphorus‐carbon‐ and phosphorus‐nitrogen‐compounds having (p‐p)π‐multiple bonds was hindered by the double bond rule. The first successful synthesis of mesomeric‐stabilized phosphorus‐carbon compounds with coordination number 2, seventeen years ago, was followed nine years later by the preparation of the imino‐phosphanes whose intensive investigation has continued to the present day. A dramatic development has now begun in the phospha‐alkene and ‐alkyne fields, and a large variety of preparative methods have been found. Several compounds of this type are amazingly stable, however they do not participate in typical ylide reactions such as the Wittig reaction. In contrast, the PC double bond is more comparable to that of olefins, which has been confirmed by the occurrence of E,Z‐isomers and pericyclic reactions of phospha‐l,5‐hexadienes.
α,ω‐Diisocyanatocarbodiimides, ‐Polycarbodiimides, and Their Derivatives
Authors: Wagner Kuno , Findeisen Kurt , Schäfer Walter , Dietrich Werner 
Published: December 2003

AbstractResearch in the field of low‐molecular weight, oligomeric and polymeric α,ω‐diisocyanatocarbodiimides and ‐polycarbodiimides has been fruitful, not only in connection with these compounds themselves, but also—as so often happens in chemistry—with quite different problems. Novel synthetic methods, discoveries concerning the properties of low‐molecular weight carbodiimides and phosphane imide derivatives, as well as results on the fragmentation reactions of four‐membered heterocyclic compounds containing oxygen, phosphorus, and nitrogen, and a better understanding of the diisocyanate polyaddition process are among the many by‐products of this research. The “high‐ and low‐temperature formation” of polycarbodiimides and the homogeneous and heterogeneous catalysis of this process are described, and the fundamental importance of four‐membered ring fragmentation mechanisms resulting in the formation of phosphane imide derivatives is outlined. Interesting building blocks for the diisocyanate polyaddition and polycondensation processes can be synthesized by many derivatization reactions of oligomeric and high‐molecular weight polycarbodiimides and polyuretonimines. The in situ production of polycarbodiimides via matrix reactions in flexible polyurethane foams leads to a cellular arrangement of the material due to the pronounced symmetrical growth processes. Combination‐foams with increased carbonation tendencies are formed in this way. Attention is drawn to several industrial applications of α,ω‐diisocyanatopolycarbodiimides, of high‐molecular weight cross‐linked polyuretonimines, and of polycarbodiimide foams.
Azaborolinyl‐Iron and ‐Cobalt Sandwich Complexes by Metal Atom Synthesis
Authors: Amirkhalili Saeid , Höhner Uwe , Schmid Günter 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 50. DOI:10.1002/anie.198200500
Activation of Silanes on a Ruthenium Cluster: Synthesis, Characterization, and Catalytic Action of the Cluster Anion [HRu3(CO)10(SiEt3)2]−
Authors: Süss‐Fink Georg 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 71. DOI:10.1002/anie.198200710
The Norbornyl Cation: Prototype of a 1,3‐Bridged Carbocation
Authors: Grob Cyril A. 
Published: December 2003

AbstractThe protracted discussion of whether 2‐norbornyl cations are bridged or unbridged, i.e. nonclassical or classical, has lost most of its meaning, because these terms apply to the extremes of a graded series of structures. This is shown by a study of the solvolysis of stereoisomeric 6‐substituted 2‐norbornyl toluenesulfonates. Norbornyl and other bicyclic cations, to which nucleophiles have limited access, are stabilized by bridging between the cationic center and a saturated carbon atom in the β‐position. Bridging is reduced by electron‐attracting substituents and by bridging.
Manganese Complexes with “End‐On” and Spirocyclic Bonded σ3,λ5‐Phosphazene Ligands
Authors: Scherer Otto J. , Kerth Jürgen , Balbach Barbara K. , Ziegler Manfred L. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 169. DOI:10.1002/anie.198201690
Non‐Planar Structures of Allyl‐ and Pentadienylmetal Compounds: Pleating to Achieve a Better Charge Distribution?
Authors: Schlosser Manfred , Stähle Manfred 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 198. DOI:10.1002/anie.198201980
Advances in Selective Chemical Syntheses of Complex Oligosaccharides
Authors: Paulsen Hans 
Published: December 2003

AbstractA wide variety of complex oligosaccharides has now been made accessible as a result of methodological improvements in the sphere of chemical synthesis, which can be used for the study of conformations and interactions with protein‐receptor molecules. Such work is of particular importance because the oligosaccharide chains of glycoproteins and glycolipids anchored to the plasma membrane are important in cell‐cell interactions and are receptors for enzymes, hormones, proteins, and viruses; furthermore, they determine the antigen properties of cells. The methods of synthesis available for the production of selective linkages in oligosaccharides are dealt with, particular attention being paid to conversion of saccharides into oligosaccharides, which are important from the biological point of view.
Liquid Structure and Thermodynamics of Alkane Mixtures
Authors: Heintz Andreas , Lichtenthaler Rüdiger N. 
Published: December 2003

AbstractSpectroscopic investigations and light scattering experiments with saturated, liquid hydrocarbons and their mixtures indicate a specific and distinct influence of the constitution, conformation, and flexibility of the molecule on the structure and macroscopic behavior of such liquids. Orientational order present in pure liquidn‐alkanes, for example, characteristically affects the thermodynamic mixing properties, such as the enthalpy of mixing ΔHMand the entropy of mixing ΔSM, when these liquids are mixed with each other, or with other liquids. Nowadays it is possible to determine thermodynamic mixing properties experimentally with such precision that systematic investigations of these properties allow the behavior of liquids to be studied qualitatively and–with molecular theories of liquids–to some extent also quantitatively. The latest results in this respect, exemplified by mixtures of alkanes, are discussed. These results not only demonstrate the progress made in understanding the relations between molecular (microscopic) and macroscopic properties, but are also of importance for industrial applications (e.g.separation processes) in which mixtures of hydrocarbons are involved.
[Fe6S9(SCH2C6H5)2]4−: A Hexanuclear Iron‐Sulfur Cluster Anion Containing the Square‐Pyramidal [(μ4‐S)Fe4] Unit
Authors: Henkel Gerald , Strasdeit Henry , Krebs Bernt 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 489. DOI:10.1002/anie.198204890
A New Route to Pyridine Derivatives: Reaction of N‐Methylene‐tert‐butylamine with Enamine
Authors: Komatsu Mistsuo , Ohgishi Hideo , Takamatsu Shigeki , Ohshiro Yoshiki , Agawa Toshio 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 483. DOI:10.1002/anie.198204830
Resolution of D‐ and L‐Amino Acids by HPLC using Copper Complexes of N,N‐Dialkyl‐α‐amino Acids as Novel Chiral Additives
Authors: Weinstein Shulamith 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 425. DOI:10.1002/anie.198204250
The Reactivity of Primary Free Radicals and Radical Ions, Mass Transfer, and Electrosorption—The Fundamental Factors for Selectivity in Electrochemical Syntheses of Organic Compounds
Authors: Wendt Hartmut 
Published: December 2003

AbstractIn many cases the electrolytic synthesis of organic compounds is rather unselective. This is because the primary radical ions and/or radicals are very often so reactive that they are able to react competitively with several of the different species present in the electrolyte. The aim is to increase the selectivity by rationally altering the process parameters; this demands a knowledge,inter alia, of electrosorption effects and of the relationships between mass transfer and chemical reaction, at or in front of the electrodes (in the so‐called reaction layer). Four examples will be used to illustrate this theme:The anodic synthesis of triarylsulfonium salts,The addition of anodically generated N3‐radicals to olefins, producing “monomeric” 1,2‐diazides and “dimeric” 1,4‐diazides,The cathodic synthesis of optically active 1‐(2‐pyridyl)ethanol,The synthesis of 1,2‐ and 1,4‐diol ethers by anodic oxidation of vinyl compounds in alcoholic solutions.
Novel Pseudooxocarbon Dianions of the C4 Series
Authors: Seitz Gunther , Sutrisno Rudianto , Gerecht Bernd , Offermann Guido , Schmidt Roland , Massa Werner 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 582. DOI:10.1002/anie.198205820
Hydroxylation of Acyclic Alkanes by Oxygen Atoms O(3P)–Comparison of Ozone and O(3P) Oxidations of Alkanes
Authors: Zadok Elazar , Mazur Yehuda 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 606. DOI:10.1002/anie.198206060
Synthesis of Macromolecular Isocyanides with General Solvent Compatibility–Novel Polymer Supports for Solid‐Phase Syntheses
Authors: Arshady Reza , Ugi Ivar 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 761. DOI:10.1002/anie.198207610
Cu‐H2 Photochemistry in the Matrix; ESR, FTIR, UV/VIS Spectroscopic and Kinetic Studies
Authors: Ozin Geoffrey A. , Mitchell Steven A. , Prieto Jamie García 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 785. DOI:10.1002/anie.198207850
A Ternary Clathrate from Cryptand, Hydroquinone and Water—Selective Formation and X‐Ray Structural Analysis
Authors: Vögtle Fritz , Puff Heinrich , Friedrichs Edmund , Müller Walter M. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 986. DOI:10.1002/anie.198209860
The Resist Technique—A Chemical Contribution to Electronics
Authors: Steppan Hartmut , Buhr Gerhard , Vollmann Hansjörg 
Published: December 2003

AbstractBesides its technical meaning, the word “electronics” signifies another industrial revolution. The driving force behind this development is the very rapid progress in the field of integrated semiconductor circuits. An ever‐increasing number of structures of ever‐decreasing size must be accommodated on the same surface of the semiconductor crystal. This trend towards miniaturization embraces not only the integrated circuit but also its mounting panel, the printed circuit board; integrated circuits with 65 536 storage spaces, i.e. more than 100 000 individual functions, on a semiconductor die of less than 1 cm2 are already standard today in industry. This micro‐world, the potential of which can hardly be fully appreciated even today, has a direct appeal to all those of scientific inclination. However, the role of chemistry in the creation of this world becomes clear only on closer examination of the manufacturing processes: no mechanical tool is fine enough and no machine is sufficiently precise and rapid to work out complicated structures in the micron range with the required perfection. Chemistry first made possible the mass production of electronic components and consequently their widespread use today, and it is chemistry which will also play a decisive role in the future. Whether in the field of photoresists for the production of printed circuit boards with conductor widths of less than 100 μm, or in overcoming the 1 μm barrier in the manufacture of semiconductors using electron beam‐ and X‐ray‐resists, photochemistry, radiation chemistry, and polymer chemistry will have to develop new manufacturing processes and provide industrially utilizable materials.
Redox Reactions of a Ferrio‐arsane and ‐stibane with Chlorophosphanes: Synthesis of a Diferrioarsonium Chloride and a Stiborane with Asymmetric Iron Atoms[1]
Authors: Malisch Wolfgang , Kaul Hans‐Achim , Gross Elisabeth , Thewalt Ulf 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1281. DOI:10.1002/anie.198212810
Support Effects on the Growth, Stabilization, and Agglomeration of Low Nuclearity Transition Metal Clusters Synthesized from Metal Atoms Vaporized into Liquid Aryl‐Substituted Polymers
Authors: Ozin Geoffrey A. , Andrews Mark P. 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1255. DOI:10.1002/anie.198212550
Metal‐Induced Decarboxylation of Diketene—A Novel Route to Allene Complexes[1]
Authors: Herrmann Wolfgang A. , Weichmann Josef , Ziegler Manfred L. , Pfisterer Heike 
Published: December 2003

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1982, 1223. DOI:10.1002/anie.198212230