bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biosynthesis, Structure, and Biological Action of the Lipids of the Tubercle Bacillus
Authors: Lederer E. 
Published: December 2003

AbstractThe extensive studies of R.J. Anderson between 1926 and 1946 nad the subsequent work of Stenhagen, Polgar, and Cason, and of the author's laboratory have demonstrated the astonishing abilities of the tubercle bacillus in synthetizing lipids. Numerous branched‐chain fatty acids, glycolipids, peptidolipids, and peptidoglycolipds have been isolated, and their structures more or less elucidated. Such work is of interest not only to natural‐priduct chemists, and biochemists, but especially to biologists and pathologists who are concerned with the harmful effects caused by the tubercle bacillus. The present article discusses chiefly three points: 1. The biogenesis of the branched‐chain fatty acids. ‐ 2. The structures of several glyco‐, peptido‐, and peptidoglycolipids. ‐ 3. Adjuvant activity and immunization by the lipids of the tubercle bacillus.
Acrolein Polymers
Authors: Schulz R. C. 
Published: December 2003

AbstractThe unsaturated aldehyde acrolein is a suitable source for different types of high polymers. If it is regarded as a 1,3‐diene analogous to butadiene, then all the known modes of its polymerization can be systematically described and further possibilities predicted. A survey is given on this basis of the results obtained during the past decade. It is shown that acrolein is one of the few monomers which contain two polymerizable groups of differing reactivities. This fact allows the formation from acrolein of new homopolymers, copolymers, and graft copolymers, a scope which is not encountered with many other monomers.
A New Method for the Determination of Fluorine
Authors: Seel F. , Steigner Elli , Burger Inge 
Published: December 2003

AbstractA new, particularly simple and reliable method of quantitative fluorine analysis is described; it is based on the conversion of insoluble silver oxide into soluble silver fluoride by fluorosilicic acid released from the sample by Willard‐Winter‐Tananaev steam distillation, the silver fluoride then being determined volumetrically according to Volhard.
A Synthetic Route to the Corrin System
Authors: Bertele E. , Boos H. , Dunitz J. D. , Elsinger F. , Eschenmoser A. , Felner I. , Gribi H. P. , Gschwend H. , Meyer E. F. , Pesaro M. , Scheffold R. 
Published: December 2003

AbstractThe synthesis of the nickel(II) complex of (±)‐1,8,8,13,13‐pentamethyl‐trans‐corrin illustrates a synthetic route to the corrin system. Repeated use of triethyloxonium tetrafluoroborate in this synthesis demonstrates the preparative value of the trialkyloxonium salts discovered by Meerwein et al.
The Modes of Reaction of Ambident Catioins
Authors: Hünig S. 
Published: December 2003

AbstractThe effect of the nature of the coreactants and the reaction conditions on the ability of certain mesomeric cations to react with nucleophilic reagents to form isomeric products has been studied. The structures of the products isolated are determined by competition between a kinetically controlled but reversible reaction and a thermodynamically controlled reaction.
Metallo‐Complexes
Authors: Bergerhoff G. 
Published: December 2003

AbstractTernary and quasiternary compounds consist of either one cationic and two anionic,or one anionic and two cationic components. The size of the ions and the bonding forces between them determine the structure of the compounds. A compound is regarded as a complex when its lattice contains structural groups in which the interaction between the constituent atoms is substantially greater than or different from that between these structural groups and the other components of the compound. Metallo‐complexes are built up of one cationic and two anionic components; in contrast to the complexes with cationic central atoms which have been thoroughly investigated, they contain an anionic central atom surrounded by cationic ligands. A list is given of many compounds which can be formulated as metallo‐complexes after discussion of methods for their preparation and their chemical properties; the reason that only few metals can function as ligands of an anionic central atom is deduced from the pertinent crystal structures.
Protonic States and the Mechanism of Acid‐Catalysed Esterification
Authors: Zimmermann H. , Rudolph J. 
Published: December 2003

AbstractProtons can be very mobile in condensed phases; the length of time they are present in any one place is minute. The significance of proton mobility in the course of chemical reactions is considered in the case of acid‐catalysed esterification by the normal carbonyl addition mechanism. – The properties of the protons in the carboxylic acid/alcohol system can be discussed on the basis of a semiconductor term diagram. The high mobility of the catalysing protons in the semiconductor system suggests that formation of the esterification intermediates occurs in two reaction steps which proceed at different rates. In the first rapid step the transition state is reached by proton transfers via hydrogen bridges. The proton rearrangement involved proceeds so rapidly that the heavy molecular skeletons retain their mutual spatial positions (Franck‐Condon principle for proton‐catalysed reactions). In the second slower step, the intermediate is formed by rearrangement of the groups of atoms. – Decomposition of the intermediate, with formation of either the starting materials or the end products, proceeds via a mechanism similar to that for the formation.
Recent Results of Configurational Research
Authors: Schlenk W. 
Published: December 2003

AbstractThe problems involved in configurational research differ from those of many of the currently important fields of general chemistry. Consequently, many chemists are less familiar with recent developements in this field than, for example, with those of the generally important modern ideas on valence and reaction mechanisms. A survey of new methods and recent results of configurational studies is attempted in this review, some unpublished experimental findings by the author being included. However, no attempt has been made to present an exhaustive review, nor to give a detailed treatment of individual problems which may interest the specialist.
The Use of Silylation in Organic Syntheses
Authors: Birkofer L. , Ritter A. 
Published: December 2003

AbstractThe term silylation is used to denote the introduction of a triorganosilyl moiety, especially the trimethylsilyl species, into organic compounds. ‐ Silylated amino acids and sugars are particularly suitable for the syntheses of peptides and saccharides, respectively, since the silyl group can be cleaved off readily under mild conditions. Many diamines undergo ring closure, e.g. with phosgene, only after silylation. ‐ O‐silylated lactim ethers (i.e. cyclic imino ethers) are converted into N‐alkyl derivatives by alkyl halides. Compounds with a strongly polarized SiC bond may be used for chain extension. Silyl esters of halogeno fatty acids yield lactones with silver cyanate. ‐ Trimethylsilyl azide is thermally very stable and behaves like organic azides. It reacts with acetylenic compounds, trialkylphosphines, and triarylphosphines to yield silylated triazole derivatives, trialkylphosphines N‐silylimines, and triarylphosphines to yield silylated triazole dervatives, trialkylphosphine N‐silylimines, and triarylphosphine N‐silylimines, respectively, from which the silyl groups can be removed under mild conditions.
Equilibrium and Transport Properties of Concentrated Electrolyte Solutions
Authors: Haase R. 
Published: December 2003

AbstractA historical survey is followed by a discussion of a number of problems associated with concentrated solutions of electrolytes containing two ion constituents: general thermodynamic properties, dissociation equilibria, phase separation, analytical representation of the thermodynamic functions over the entire range of concentrations, and general relationships in electrical conductivity, diffusion, and sedimentation. A number of relationships valid at all concentrations is formulated, and known relationships pertaining to dilute solutions are derived from these as special cases. The discussion of concentrated solutions is illustrated by numerical examples, most of which are based on recent results.
Chemiluminescence in Organic Compounds
Authors: Gundermann K.‐D. 
Published: December 2003

AbstractAs a result of the development of very sensitive equipment, it is now possible to show that the chemiluminescence of organic compounds in solution is quite a common phenomenon. Notable advances have been made during recent years in the investigation of the chemiluminescence of substituted phthalic acid hydrazides and related compounds. A new and probably generally applicable method of producing chemiluminescence has recently been discovered in the reaction of aromatic free‐radical anions with appropriate free‐radical cations.
Conformational Analysis of Cyclohexane Derivatives by Nuclear Magnetic Resonance Spectroscopy
Authors: Franklin N. C. , Feltkamp H. 
Published: December 2003

AbstractNuclear Magnetic Resonance is today one of the best methods available for the conformational analysis of cyclohexane derivatives. It is possible with this technique to investigate the spatial orientation of the substituents in fixed molecules, as well as the equilibrium position in mobile systems. For these determinations the areas under the signals, the chemical shifts, the coupling constants, and the band widths of particular signals can be used.
Applications and Limitations of Magnetic Methods in Free‐Radical Chemistry
Authors: Müller E. , Rieker A. , Scheffler K. , Moosmayer A. 
Published: December 2003

AbstractThe paper describes the application and limitations of magnetic methods to the problems of free‐radical chemistry (detection and quantitative investigation of the free‐radical state, relationships between structure and free‐radical formation, “distribution” of the unpaired electron, detection of mesomeric C, O, N, P, As, and Sn radicals, g‐factors, triplet states, and hyperfine structure). The problem of the diradical is described, and the paper closes with a discussion of the “Selwood effect”.
Compounds of Phosphorus with Silicon and Aluminum
Authors: Fritz G. , Becker G. , Poppenburg G. , Rocholl M. , Trenczeck G. 
Published: December 2003

AbstractThe formation and properties of silicon‐phosphorus and aluminum‐phosphorus compounds are described. Silylphosphines are decomposed solvolytically by H2O, C2H5OH, NH3, hydrogen halides, C2H5I, and boron halides at the SiP bond; decomposition may be preceded by formation of an addition compound. Extensive side reactions during the reaction of halogenosilanes with LiPEt2The following abbreviations are used in this paper: Et = C2H5; Me = CH3; M = alkali metal
(formation of Et2PPEt2, HPEt2, Si‐rich residues) are due to an excess of LiPEt2 in the reaction mixture. The reaction of LiPEt2 with AlCl3, AlHCl2, and AlH2Cl leads to definite aluminum‐phosphorus compounds if only one PEt2 group is present per Al atom, e.g. in (Cl2Al–PEt2)3, or if salts such as Li[Al(PEt2)4] and Li[AlH2(PEt2)2] can be formed with an excess of LiPEt2.
The Significance of Enterobacterial Mutants for the Chemical Investigation of their Cell‐Wall Polysaccharides
Authors: Lüderitz O. , Westphal O. 
Published: December 2003

AbstractThe outer cell surface of Enterobacteriaceae, i.e. the cell wall, consist of a rigid structure (murein) on which additional proteins, lipids, and polysaccharides are deposited. In the bacterial wild types (S forms) the polysaccharide is species‐specific and carries the serologically determinant groups of the respective O antigen. These specific polysaccharides often consist of a large number of monosaccharides; up to eight different monosaccharides may be involved. Bound to lipid A, the cell‐wall lipopolysaccharides represent the endotoxins of the bacteria. During the past few years the structures of the enterobacterial cell‐wall polysaccharides have been elucidated by chemical, immunochemical, biochemical, and genetic investigations, particularly in the Salmonella. Here the polysaccharides consists of a basal polysaccharide common to all species, to which (in the S form) are bound longer species‐specific side chains, consisting of repeating oligosachharide units. Spontaneous S → R mutation leads to R forms which are deficient mutants of the wild types in regard to the biosynthesis of the complete cell‐wall polysaccharide. In contrast to the multiplicity of the serological specificities of the somatic antigens of the S forms, only a few serological types were found among the R forms (R I, R II, etc.). These R polysaccharides correspond to intermediates in the biosynthesis of the wile‐type polysaccharides. The S → R mutation leads to the loss (or block) of an enzymes (transferase, synthetase) participating in the synthesis of the S polysaccharides. Recently many deficient mutants have been isolated and analysed, and in this way numerous stages in the biosynthesis of the cell‐wall polysaccharides, for example, of Salmonella minnesota, have been made accessible to direct analysis. According to these investigations, the cell‐wall polysaccharides of Salmonella consist of a basic polyheptose phosphate core which is bound to lipid A via ketodeoxyoctonic acid. To the basic core are linked pentasaccharide units of

equation image

(R II structure). All other R forms are structurally deficient mutants of R II. In the complete polysaccharides of Salmonella S forms (wild types), the repeating oligosaccharide units of the specific side, chain are bound to the terminal N‐acetylglucosamine of the R II structure.
Scrambling Equilibria and Analysis of Labile Mixtures
Authors: Van Wazer J. R. , Moedritzer K. 
Published: December 2003

AbstractIn this brief review, it is attempted to point up the importance of chemical equilibria in structural inorganic chemistry and to show how the kind and yield of various molecules may be treated quantitatively. Because of the importance of kinetic control in organic chemistry and because the chemistry of carbon compounds is by far the most advanced branch of general and descriptive chemistry, preparative inorganic chemists have often overemphasized the value of reaction‐mechanism theory to their studies and have thereby neglected the powerful quantitative approach of thermodynamics which may be used in equilibrated systems. The general theorems for treating in terms of small molecular segments the multitude of equilibria present in families of compounds are surveyed superficially with the hope that the interested reader will turn to the original papers for details. Not only physical‐inorganic chemists, but also those interested solely in preparative work can advantageously employ the theoretical ideas discussed.
Classification and Analysis of NMR Spectra
Authors: Dischler B. 
Published: December 2003

AbstractThe use of nuclear magnetic resonance as the basis of a spectroscopic method in organic analysis is steadily growing.K. H. Hauser, Angew. Chem. 68, 729 (1956). J. D. Roberts, Angew. Chem. 75, 20 (1963); Angew. Chem. internat. Edit. 2, 53 (1963).
. The object of the present article is to present a general picture of the classification and interpretation of the NMR spectra obtained at high resolutions. In simple cases complete interpretation is possible with the aid of only a few equations; otherwise it is often necessary to use a laborious mathematical procedure, which is discussed here. For a more profound study, the reader is referred to more detailed publications.J. A. Pople, W. G. Schneider, and H. J. Bernstein: High–resolution Nuclear Magnetic Resonance, McGraw Hill, New York 1959.
L. M. Jackmann: Appplications of Nuclear Magnetic Resonance Spectroscopiy in Organic Chemistry. Pergamon Press, London 1959.
P. L. Corio, Chem. Reviews 60, 363 (1960).
J. D. Roberts: An Introduction to the Analysis of of Spin‐Spin Splitting in High‐Resolution Nuclear Magnetic Resonance Spectra. Benjamin, New York 1961.
J. Ranft, Fortschr. Physik 9, 149 (1961). H. Strehlow: Magnetische Kernresonanz und chemische Struktur. Steinkopff, Darmstadt 1962.
Alcohols as Petrochemicals
Authors: Kropf H. 
Published: December 2003

AbstractEfficient processes have been developed in recent years for the large‐scale manufacture of alcohols from petrochemicals. These allow production of aliphatic alcohols both with short and with long alkyl groups more economically than was previously possible by fermentation. In this paper the most important principles and the technical execution of the hydration of olefins, the air oxidation of paraffins, and especially the synthesis reactions (e.g. the catalytic hydroformylation of olefins with carbon monoxide and hydrogen according to Roelen, the Reppe synthesis, and the Ziegler growth reaction with ethylene and triethylaluminum) are described.
Coupling Principles in Organic Dyes
Authors: Dähne S. , Leupold D. 
Published: December 2003

AbstractDye molecules containing two or more polymethine structural units, or at least one polymethine and one polyene structural unit, generally exhibit coupling effects that determine the spectroscopic behavior and other physicochemical properties of the substance. The coupling concept can be used inter alia to fit the quinone dyestuffs, the indigoids, and the indanthrenes into a general poymethine color system and to perdict new dye structures.
Reactions of Halogen Azides
Authors: Dehnicke K. 
Published: December 2003

AbstractUntil recently, the explosive nature of halogen azides made these compounds unsuitable for preparative uses and greatly impeded investigation of their physical properties. Reactions of ClN3 and BrN3 with metal halides, metal carbonyls, and organometallic compounds to from metal azide halides, nitride halides, carbonyl azide halides, and alkylmetal azides were reported only very recently. The stability relationships of the halogen azides are discussed.
Additions to the Activated CC Triple Bond
Authors: Winterfeldt E. 
Published: December 2003

AbstractThe possibilities of additions to the activated CC triple bond are discussed with the aid of a number of examples. The additions of donors that contain no active hydrogen are generally initiated via a dipolar primary complex, which can undergo stabilization by rearrangement, cyclization, or addition reactions. Preparative aspects of these reactions are also discussed. They offer routes for the preparation of heterocycles, particularly pyrrole and thiophene derivatives.
Sigma‐Bonded Organochromium Compounds. Hydrogen Transfer Reactions
Authors: Zeiss H. H. , Sneeden R. P. A. 
Published: December 2003

AbstractThe preparation and properties of two classes of organochromium compounds and their interconversion have been studied actively in recent years. These are the σ‐bonded organochromium compounds in which alkyl, aryl, or aralkyl groups are covalently bonded to chromium (II or III) and the π‐arenechromium complexes in which “aromatic” nuclei are covalently bonded to chromium (0 or I). From certain reactions of the σ‐bonded organochromium compounds, evidence has accumulated which shows that the chromium atom acts not only as a coordination center, but also as a hub for hydrogen transfer and H/D exchange[1,2]. σ‐Organochromium compounds may act as sources of radicals and carbanions. The present paper deals with the preparation and properties of σ‐bonded organochromium compounds; particular attention is given to hydrogen transfer reactions and rearrangements to bis(π‐arene)chromium complexes.
Spatial Arrangement and Preparative Organic Synthesis
Authors: Velluz L. , Valls J. , Mathieu J. 
Published: December 2003

AbstractThis review deals with the stereoselective formation of organic compounds. A number of examples of such syntheses, especially those of alkaloids and steroids, are described. An asymmetric synthesis, which avoids the intricacies and wastefulness of optical resolution, has been successful in a few cases only. The procedures of configurational change and of optical resolution, as well as the planning of multi‐step stereoselective syntheses, are discussed.
Recent Developments in the Stereochemistry of Cyclopropane Ring Opening
Authors: Sarel S. , Yovell J. , Sarel‐Imber M. 
Published: December 2003

AbstractThis review article deals with the stereochemistry of the following ring opening reactions: 1. Homoallylic rearrangement of secondary and tertiary cyclopropyl alcohols in the presence of electrophilic reagents, 2. The addition of carboxylic acids to vinylcyclopropanes, 3. The thermal rearrangement of vinylcyclopropanes into cyclopentenes. An account is also given of the NMR spectroscopic determination of the conformations of substituted vinylcyclopropanes.
Studies on the Adsorption of Gases on Clean Metal Surfaces with the Aid of Field‐Emission and Field‐Ion Microscope Techniques
Authors: Sachtler W. M. H. 
Published: December 2003

AbstractStudies on the adsorption of gases such as xenon, hydrogen, nitrogen, and carbon monoxide on the surface of a single crystal of tungsten with the aid of field‐emission and field‐ion microscopy have, in the past few years, led to new, fundamental insights into chemisorption and heterogeneous catalysis. Important phenomena which were discoverd and elucidated by these techniques include the pronounced face specificity of the adsorption, the fact that several different adsorption complexes of a gas are found on one and the same crystal face, and the rearrangement of the surface atoms through chemisorption. Many of the interpretations thus gained for the systems studied can also be generalized for other chemisorption complexes.
Tetraaminoethylenes as Strong Electron Donors
Authors: Wiberg N. 
Published: December 2003

AbstractDepending on the nature of the electron acceptor and of the tetraaminoethylene (TAE), the electron pairs of the ethylenic double bond (A), of the nitrogen (B), or of the entire electronic system (C) of TAE react with the acceptor. Thus oxidizing agents convert TAE into the mono‐and dications TAE+ and TAE2+ by path (A); acids add on to the ethylenic carbon (A) or the amine nitrogen (B) (the addition of acid is often followed by cleavage of the CC or CN bond); organic π‐electron acceptors from deeply colored donor‐acceptor complexes with TAE (C).
Oligophenyls, Oligophenylenes, and Polyphenyls, a Class of Thermally Very Stable Compounds
Authors: Ried W. , Freitag D. 
Published: December 2003

AbstractThe classical and modern syntheses of oligophenyls and polyphenyls are compared to illustrate the value and the range of applications of the preparation methods described. The investigations showed a relationship between the number, arrangement, and substitution of the aromatic rings and the physical properties of the products. The melting point of the p‐polyphenyls rises with increasing degree of condensation. Methylation, and linkage in the m‐positions lowers the melting point and at the same time improves the solubility. o‐Oligophenyls melt at lower temperatures than the p‐isomers. The highest‐melting substance in this class in p‐septiphenyl, which melts at 545 °C.
Chalcogenocarbonic Acids and Their Anions
Authors: Dräger M. , Gattow G. 
Published: December 2003

AbstractCarbonic acids in which the oxygen has been wholly or partly replaced by sulfur, selenium, and/or tellurium are known as “chalcogenocarbonic acids”. The aim of the present article is to review existing knowledge of these acids and so establish a basis for further systematic syntheses. The anions required for the synthesis of chalcogenocarbonic acids will also be briefly characterized.
Transport Phenomena in Membranes
Authors: Läuger P. 
Published: December 2003

AbstractThe realization that many elementary biological processes occur at membrane‐like structures has led to renewed interest in the theory of molecular transport through membranes. Coupling phenomena in membranes, some of which are very complex, can now be rationally described with the aid of the thermodynamics of irreversible processes. The investigation of theoretical membrane models has proved a valuable complement to the thermodynamic method.