bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemistry in Interstellar Space and Reactions Generating Interstellar Molecules
Authors: Breuer H. D.
Published: December 2003

Over 20 different molecules and radicals have so far been detected in interstellar space. The number of such molecules and radicals and their frequently complicated structure raise the question of the processes leading to their formation. Diatomic molecules and radicals could arise in gas‐phase reactions. Formation of polyatomic molecules can be explained in terms of reactions proceeding on the surface dust particles and possibly involving interstellar radiation. The author demonstrates, with the aid of a model, that the molecular abundances and distributions within dust clouds in certain regions can be explained by photocatalytic reactions.
State of Development of Atomic Absorption Spectrometry [New analytical methods (1)]
Authors: Massmann Hans
Published: December 2003

Atomic absorption spectrometry has developed extremely rapidly in recent years, and is now used in many analytical laboratories. The purpose of this progress report is to show the present position and to examine critically the possibilities and limitations of atomic absorption methods.
Isopeptide Crosslinks—Their Occurrence and Importance in Protein Structure
Authors: Asquith R. S. , Otterburn M. S. , Sinclair W. J.
Published: December 2003

Isopeptide links refer to bonds between the ϵ‐amino group of lysine and the side‐chain carboxyl groups of glutamic or aspartic acid. Covalent crosslinks of this kind, which undoubtedly occur in protein feedstuffs and reduce their nutritional value, also participate In the fibrinogen → fibrin transformation and play a part in stabilizing the structure of keratins. Isopeptide links also arise on heating of both fibrous and globular proteins, the amount formed depending upon the severity of heat treatment. The mode of formation and the significance of these crosslinks require further elucidation.
Effects of Through‐Bond Interaction
Authors: Gleiter Rolf
Published: December 2003

The effect of through‐bond interaction is derived for 1,4‐butanediyl as an example, and changes caused by this effect in the ground state of the system are demonstrated. Spectroscopic methods for the detection of the effect are discussed, and its chemical consequences are illustrated by a number of examples.
Prescriptions and Ingredients for Controlled CC Bond Formation with Organometallic Reagents. New synthetic methods (5)
Authors: Schlosser Manfred
Published: December 2003

Merits and drawbacks of known carbon‐carbon linking procedures are outlined. Two novel methods are discussed in some detail: the copper‐catalyzed alkylation of Grignard reagents and reactions with allylpotassium compounds. Both methods provide a very efficient access to saturated, unsaturated, as well as functionally substituted hydrocarbons and moreover permit an astonishing degree of regio‐ and stereoselective control of olefin synthesis.
Biochemistry of the Peroxisome in the Liver Cell
Authors: Sies Helmut
Published: December 2003

The marker enzyme of the peroxisome—a phylogenetically old yet only recently discovered cell organelle—is catalase, a hemoprotein which decomposes hydrogen peroxide catalatically as well as peroxidatically. In the peroxisomes, catalase is associated with H2O2‐producing oxidases and other enzymes. Also in parenchymal cells such as liver and kidney cells part of the reduction of oxygen occurs via formation of H2O2. A central role in peroxisomal H2O2‐metabolism is played by the active intermediate, catalase‐Fe3+‐H2O2, (Compound I), which is distinguished from free catalase by specific absorption bands. Organ photometry on intact hemoglobin‐free perfused rat liver in order to measure Compound I selectively provides a direct insight into the dynamics of the H2O2 metabolism which takes place in the range of nanomolar concentrations. Endogenously, 1g of liver forms approximately 50 nmol of H2O2 per min. The turnover number, which in the steady state is < 10 min−1 in the cell as compared to > 108 min−1 for the isolated enzyme with an excess of substrate, can be increased to approximately 102 min−1 by intracellular stimulation of the H2O2 production (e.g. by glycolate or urate). The peroxidatic oxidation of hydrogen donors (e.g. methanol and ethanol), favored relative to the catalase pathway at low turnover numbers, is of importance in normal metabolism and in pathological conditions.
Specific Interactions. Intermolecular Forces, Steric Requirements, and Molecular Size
Authors: Simon Zeno
Published: December 2003

Specific interactions or recognition processes are extremely important in many fields of chemistry and biology: typical examples are the enzyme‐substrate and the antigen‐antibody reactions. Quantitative predictions require a knowledge of steric fit, intermolecular forces, and molecular size. These considerations should facilitate design of new drugs.
α‐Metalated Isocyanides in Organic Synthesis. New synthetic methods (6)
Authors: Hoppe Dieter
Published: December 2003

α‐Alkali‐metalated isocyanides, which can be obtained from isocyanides and bases, can be used for nucleophilic introduction of (masked) α‐aminoalkyl groups. Intramolecular ring‐closure may then follow if a nucleophile combines at the electron sextet of the isocyanide carbon. Treatment of α‐alkali‐metalated isocyanides with electrophilic agents permits rapid and efficient synthesis of, inter alia, 2‐ and 3‐amino alcohols, straight‐chain, branched, and β‐functional α‐amino acids, olefins, vinyl isocyanides, and of a large number of mainly five‐, but also six‐ and seven‐membered aza‐, diaza‐, oxa‐aza‐, and thia‐aza heterocycles.
The Replacement of Phosphates in Detergents—Possibilities and Limits
Authors: Berth Peter , Jakobi Günter , Schmadel Edmund , Schwuger Milan J. , Krauch Carl Heinrich
Published: December 2003

Elimination of phosphates from detergents alone, is insufficient to solve the eutrophication problem. Nevertheless, the endeavors of the detergent industry are aimed at finding phosphate subsitutes. Novel approaches for at least a partial replacement of detergent phosphates have been found by using water‐soluble organic complexing agents as well as heterogeneous organic or inorganic ion exchangers. So far, a large‐scale replacement is not possible. It is not justifiable until all technical requirements are met with and safety with regard to man, animals, plants and drinking water has been established.
What Do We Know About Nuclear Fission?
Authors: Aumann Dieter C.
Published: December 2003

Nuclear fission, although a physical phenomenon, is also of interest to the chemist. It was discovered by chemists, and chemists have made a material contribution to our present knowledge in this field. A comprehensive theory of nuclear fission has not, as yet, been developed, despite the volume of experimental data that has amassed in the 35 years since its discovery. In the past few years discoveries have been made which cannot be explained with conventional theoretical models of nuclear fission. The most important discovery was that of shape isomerism, a novel type of nuclear isomerism. It would appear that an accurate calculation of fission barriers is a prerequsite for precise explanation of many experimental findings. Recent results in this connection and an outline of the present state of our knowledge of nuclear fission constitute the main theme of this paper.
Synthetic Reactions of Metal Atoms at Temperatures of 10 to 273°K
Authors: Timms Peter L.
Published: December 2003

Metal atoms, easily formed by vaporizing metals at high temperatures under vacuum, are reacted with inorganic and organic compounds in solution at 80 to 273°K or by co‐condensing the atoms and substrate vapors at 10 to 80°K. Gram quantities of products containing metals in low valency states can be isolated in many cases, and some of the compounds formed are inaccessible by conventional synthetic routes.
The Photochemistry of Organic Solids
Authors: Cohen Mendel D.
Published: December 2003

During the years that he was at the Weizmann Institute of Science the late G. M. J. Schmidt initiated and developed a very vital research program on the relationship between the structures of organic crystals and the reactions which occur in these crystals. As the program developed the “solid‐state group” became larger and more diversified—X‐ray crystallographers, organic chemists, spectroscopists, and even theoreticans had their contributions to make. Professor Schmidt died in 1971. As one of the members of this group, I here present a review of recent developments in parts of the field of interest to me.

Of the reactions of organic crystals which have been studied thus far a large number are induced by light and other radiation. This is because radiation, unlike most chemical reactants, can readily penetrate the surface of the crystal, and thus reach the sites one wishes to activate. It is my aim in this article to point out some of the principles operative in the photochemistry of organic crystals. I shall choose examples to illustrate these principles and will not attempt to cover all the various types of reaction and systems which have been studied.

It is appropriate at this stage to pay tribute to the memory of another great scientist who recently passed away—Theodorr Föster. Many of the ideas which I develop here are extensions of Professor Förster's earlier work, as are so many of the recent developments in photochemistry.
Stereochemistry of Reaction Paths as Determined from Crystal Structure Data—A Relationship between Structure and Energy
Authors: Bürgi Hans‐Beat
Published: December 2003

The three‐dimensional structure of frequently occurring molecular fragments has been studied systematically. Molecular subunits which were examined include hydrogen bridges (O—HċO), triiodide anions (I−3), other linear triatomic fragments (Cl—SbċCl, S—SċS, Mo—OċMo), tetrahedral ions (SO2−4, PO3−4, AlCl−4) and related species (MSO3, etc.), molecules containing both keto‐ and amino‐groups (mostly alkaloids), substituted [10]annulenes and cycloheptatrienes, organic five‐membered rings, and five‐coordinated metal and nonmetal atoms. The bond distances and angles describing the structure of a giving fragment cover a range that is many times larger than the range of the experimental standard deviations. The changes of the various structural parameters of a fragment are correlated with each other. The observed mutual dependence (structural correlation) may be described by means of Pauling's equation relating bond length r to bond number n:r = r0 ‐ clogn. The bond numbers n are expressed in terms of bond angles. The sum of bond numbers at a given atom is roughly constant and does not depend on the environment. “Standard bond lengths” of a fragment are determined by a least‐squares procedure based on all available data. They are supplemented by curves that describe the observed distortions.

The shape of these correlation curves is reminiscent of the structural changes occurring along the pathways of chemical reactions, e.g. nucleophilic substitution at tetrahedrally coordinated atoms (SN1 and SN2), nucleophilic addition to carbonyl groups, electrocyclic ring closure of polyenes, pseudo‐rotation of five‐membered rings or Berry pseudo‐rotation. For many of these reactions approximate energy hypersurfaces have been obtained from quantum mechanical calculations, model force fields and from spectroscopic information (IR, NMR). Comparison between reaction pathways determined from structural correlations with those obtained from models of the energy surfaces shows fair agreement.
Nonenzymatic Simulation of Nitrogenase Reactions and the Mechanism of Biological Nitrogen Fixation
Authors: Schrauzer G. N.
Published: December 2003

The development of biologically relevant model systems of nitrogenase permitted the simulation of virtually all known reactions of the nitrogen reducing enzymes under nonenzymatic conditions. On the basis of these experiments, a mechanism of biological nitrogen fixation is formulated which is in accord with the available enzymological evidence. The key reactions of the substrates of nitrogenase occur at a molybdenum active site. The non‐heme iron, which is bound to sulfur and protein‐S⊝ groups, mediates the transport of electrons to the molybdenum active site but does not participate directly in the reduction of the substrates. ATP is required for the acceleration of the reduction and activation of the molybdenum site and is hydrolyzed to ADP and inorganic phosphate. Diimine and hydrazine were detected as intermediates in the reduction of molecular nitrogen under nonenzymatic conditions.
Heterocyclic Systems Having Eight π‐Electrons. Synthesis, Properties, and Significance
Authors: Schmidt Richard R.
Published: December 2003

The terms “aromatic” and “antiaromatic” have attracted widespread interest in recent years. After all the discussion about the meaning of words, one fact remains: the energy content of planar systems displaying cyclic electron delocalization depends upon the number of, and the orbital interactions between, the participating electrons. The concept underlying this progress report is that the electronic destabilization of systems having eight π‐electrons should be especially pronounced in the case of six‐membered rings for steric and electronic reasons. Such systems are found primarily in anionic, but also in neutral, heterocycles containing hetero ring members which possess electron pairs capable of delocalizing into the π‐system. The production and reactivity of such systems are investigated and their biological significance discussed.
The Pyruvate Dehydrogenase Multienzyme Complex
Authors: Hucho Ferdinand
Published: December 2003

The three enzymes pyruvate dehydrogenase, dihydrolipoamide transacetylase, and dihydrolipoamide dehydrogenase constitute the pyruvate dehydrogenase multienzyme complex of E. coli; in mammals the complex also contains a kinase and a phosphatase. Multienzyme complexes are structural, functional, and regulatory units enabling the organism to operate more economically than with single enzymes. The pyruvate dehydrogenase multienzyme complex may stand at the switch‐point between energy metabolism and gluconeogenesis.
Tertiary Phosphane/Tetrachloromethane, a Versatile Reagent for Chlorination, Dehydration, and PN Linkage
Authors: Appel Rolf
Published: December 2003

In this review the processes occurring on the treatment of triphenylphosphane with tetrachloromethane are first reported; a key role is played here by (trichloromethyl)phosphonium chloride which reacts with a further amount of the phosphane to give the stable salt [chloro(triphenylphos‐phoranediyl)methyl]triphenylphosphonium chloride by way of dichlorophosphorane and (dichloromethylene)phosphorane that is detectable only as an intermediate. The preparative application of the two‐component system as a chlorinating, dehydrating, and P—N‐linking reagent is ascribable to “phosphorylation”

Here and below, “phosphorylation” is used lo mean in general the formation of a phosphorus derivative. In the narrower sense this term denotes the introduction of phosphoryl groups P(O).

of the substrate in question through several reactive species. In these applications the reactions with the substrate compete with reactions of the two‐component system with itself, so that the overall course of the reaction is in nearly all cases much more complex than was previously assumed. Nevertheless. very good results can be achieved by the use of this reagent, high yields and mild reaction conditions being characteristic.
Chemistry and Biochemistry of Unsaturated Fatty Acids
Authors: Kunau Wolf‐H.
Published: December 2003

Although unsaturated fatty acids have long been known to accompany saturated fatty acids in most lipids, qualitative and quantitative determination of fatty acid patterns only became possible with the advent of modern analytical methods. Present day knowledge of the chemical structure, physical properties, and metabolism of unsaturated fatty acids provides the basis for the development of new concepts of their function. Thus unsaturated fatty acids crucially determine the properties of biological membranes. Moreover, essential fatty acids are precursors of prostaglandins.
Unusually High Barriers to Rotation Involving the Tetrahedral Carbon Atom
Authors: Ōki Michinori
Published: December 2003

Rotation about CC single bonds in suitably substituted compounds gives rise to rotational isomers (also called rotamers) which can be isolated if the barrier to rotation is high enough. The present article considers derivatives of triptycene and fluorene whose barriers to rotation are of the order of 30 kcal/mol.
Oxidation‐Reduction Condensation
Authors: Mukaiyama Teruaki
Published: December 2003

This review is concerned with syntheses which can be carried out in the absence of acids and bases. In the case of condensations, i.e. the union of two or more reaction partners with elimination of simple molecules such as H2O or NH3, the combination of a weak oxidizing agent with a weak reducing agent has proven useful. A particularly suitable reagent for condensations with elimination of water is triphenylphosphane/di(2‐pyridyl)disulfane. The phosphane takes up the oxygen atom and is converted into the phosphane oxide, while the disulfane reacts with the two hydrogen atoms to form pyridinethione. Oxidation‐reduction condensations have been utilized for the preparation of, inter alia, esters, peptides, nucleotides, and macrolides.
Integrated Dust Analysis by Physical Methods
Authors: Malissa Hanns
Published: December 2003

Environmental analyses show that the air which we breathe, and which is so essential to life, is in general a mixture of gaseous, liquid, and solid components. The solid airborne particles, whose concentration, homogeneity, chemical composition, size, and shape can vary over wide ranges, and whose origin may be “natural” or “artificial” are referred to as “dust”. Dust particles can act, inter alia, as condensation nuclei, catalysts, and directly as hazardous materials. Unfortunately, we still know far too little about dust. Dust analysis is extremely difficult and challenging, even for modern analytical chemistry; it is still far from being fully automated. The simultaneous determination of as many “dust parameters” as possible, and particularly the synoptic consideration of all available data against a background of physicochemical and technological knowledge on the development, transformation, and effects of dust, are summarized as “integrated dust analysis”.
The Analogy between O and C(CN)2
Authors: Wallenfels Kurt , Friedrich Klaus , Rieser Jürgen , Ertel Werner , Thieme Herbert K.
Published: December 2003

The compounds of oxygen, i.e. OH acids, ethers, quinones, aldehydes, ketones, carboxylic esters and amine oxides, sulfoxides, and phosphane oxides, are compared and contrasted with those compounds which contain a C(CN)2 moiety in place of the characteristic O atom. In their typical properties the pairs of analogs frequently display surprising agreement. The purpose of such analogy studies lies primarily in the estimation of reactivities; their limits are reached where specific properties of the structual components become effective.
The Synthetic Utility of 2‐Oxazolines
Authors: Meyers A. I. , Mihelich E. D.
Published: December 2003

The oxazoline ring system, first prepared in 1884, has only in the last five years been shown to possess considerable utility in the synthesis of a variety of functionalized organic compounds. By appropriate metalation of the 2‐alkyl substituent it is possible to prepare a variety of homologated carboxylic acid derivatives, both chiral and achiral. Various other manipulations of the oxazoline ring lead to aldehydes, ketones, lactones, amino acids, thiiranes, and olefins. Due to the inertness of the oxazoline ring system to various reagents (RMgX, LiAlH4, CrO3, mild acid or alkali) it may be utilized as a protecting group for carboxylic acids during the transformations involving the above reagents. Two major new developments in oxazoline chemistry involve (a) the use of a chiral oxazoline as a reagent for asymmetric synthesis of chiral carboxylic acids, lactones, alcohol, thiiranes, and olefins and (b) a new mode of aromatic substitution in which the aryloxazolines act as nucleophilic or electrophilic reagents. This behavior has led to a variety of polysubstituted benzenes and biphenyls which would be inaccessible by classical routes. A variety of examples illustrating the utility of oxazolines indicated above are presented so that the reader may appreciate the vast potential of this simple ring system in synthesis.
The Chemistry of Simple Phosphorus‐Carbon Compounds
Authors: Harnisch Heinz
Published: December 2003

With the aid of selected examples an overview is given of the development trends in phosphoruscarbon chemistry over the past few years. An attempt is made to demonstrate the relationships between various parameters and properties such as constitution, basicity, substitution by functional groups, reaction behavior etc. of the compounds. In the case of basis compounds containing methylphosphorus groups the state of development of industrially interesting processes is also outlined. In addition, the synthesis of a few bifunctional phosphorus‐carbon compounds which can be employed as comonomers in the production of polymers is described.
Polar Effects in Organic Reactions
Authors: Grob Cyril A.
Published: December 2003

Attempts to gauge the effect of polar substituents on organic reaction rates by means of “inductive substituent constants” are based on the assumption that these effects are independent of the type of reaction observed. The measured rate constants of nucleophilic substitution reactions show, however, that this assumption is only partly justified even for saturated molecules. It is invalid if the substituent and the reaction center are an electron donor and an electron acceptor, respectively, which are hyperconjugated by way of σ‐bonds. In extreme cases the resulting polarization can lead to heterolytic fragmentation.
Kink‐Block and Gauche‐Block Structures of Bimolecular Films
Authors: Lagaly Gerhard
Published: December 2003

Layer silicates and some other layer compounds can take up organic compounds such as long‐chain alkanols and alkylammonium ions with formation of ordered bimolecular films. This system enables new ideas to be developed concerning the structure of monomolecular and bimolecular films: the films form reversible kink‐block and gauche‐block structures. Conclusions can be derived about the structure of the lipid layers in membranes.
Dual‐Wavelength Spectrophotometry
Authors: Shibata Shozo
Published: December 2003

At present, dual‐wavelength spectrophotometry is probably the least well known of the techniques of absorption spectrophotometry. However, recent improvements in application techniques have shown that for various organic and inorganic materials dual‐wavelength spectrophotometry can provide higher sensitivity and selectivity than conventional spectrophotometry. This article reviews the principles and scope of dual‐wavelength spectrophotometry, including derivative absorption spectrophotometry, in the hope that these techniques may be adopted more frequently in the future for resolving many analytical problems.
Nucleophilic Substitution of Vinylic Hydrogen Atoms by Carbanions
Authors: Reetz Manfred T. , Schinzer Dieter
Published: December 2003

Chain elongation of activated terminal olefins can be accomplished by the reaction sequence (1)→(2)→(3). It is also feasible with R = tert‐butyl, cyclopropyl, and other bulky groups.
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Cyclometalation Reactions
Authors: Bruce Michael I.
Published: December 2003

Reactions of transition metal complexes in which an organic ligand undergoes intramolecular metalation with formation of a metal‐carbon σ bond are termed cyclometalation reactions. This article provides a general summary of our knowledge of these reactions, and discusses them in terms of their scope, mechanisms, and utility in organic synthesis, particularly of heterocyclic molecules.
Early History of the Quantum Mechanical Treatment of the Chemical Bond
Authors: Hund Friedrich
Published: December 2003

Formulation of the Schrödinger equation (1926) laid the foundation for a theory of the electronic structure of molecules, and thus for a physically sound theory of the homopolar chemical bond. Physicists reached a qualitative understanding of the bond in diatomic molecules during the ensuing years 1927 to 1929, and of stereochemistry by 1931.
The Surface Chemical Bond
Authors: Somorjai Gabor A.
Published: December 2003

Adsorbed particles can be bound chemically to the surface of a solid (chemisorption). Modern variants of electron diffraction and electron spectroscopy now enable us to gain an insight into the nature of such surface chemical bonds, which play a key role in heterogenous catalysis and many other technically important phenomena such as adhesion, lubrication etc. Predominantly localized surface bonds can be compared to the covalent bonds in cluster compounds.
Isolation and Vibrational Spectra of Bond‐Isomeric Hexakis(thiocyanato‐isothiocyanato) Complexes of Ruthenium(III) and Osmium(III)
Authors: Schwerdtfeger Hans‐Joachim , Preetz Wilhelm
Published: December 2003

The ambidenate ligand SCN− can bond via S (thiocyanato) or N (isothiocyanato). High voltage electrophoresis resolved the RuIII complex (1) in to four bond isomers, and the OsIII complex (2) into three such isomers, which were identified by their vibrational spectra.
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Determination of Reaction Enthalpy in the Ion‐Exchange of Chlorine Isotopes
Authors: Heumann Klaus G. , Hoffmann Rainer
Published: December 2003

Isotope exchange equilibrium of chloride ions according to eq. (1) has now been characterized thermodynamically. A knowledge of thermodynamic data is an important requirement for developing chromatographic processes intended for chemical pre‐enrichment of chlorine isotopes.
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(Chloromethylene)triphenylphosphorane
Authors: Appel Rolf , Morbach Wolfgang
Published: December 2003

The missing compound (Chloromethylene)triphenylphosphorane (2) occupying an intermediate position between methylene‐ (1) and (dichloromethylene)triphenylphosphane cannot be prepared by analog with the other two ylides. Pure (2) has now been obtained by transylidation.
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Utilization of Microbes—Modern Developments in Biological Technology
Authors: Präve Paul
Published: December 2003

Until recently microbiology had found use only in the foodstuffs sector and in the production of antibiotics; however, the production of biomass should be regarded as the key development of the new science of biotechnology. The biomass consists of fatty and protein‐rich microorganisms that can be used for example in animal feeds. The microorganisms grow not only on cellulose waste and other biological substrates but also, for example, on petroleum and methanol. Their energy demand is comparatively low. It is being realized more and more that inflexible technologies pose problems for our civilization and that biotechnology, which utilizes the cyclic metabolic pathways of microorganisms and often recycles waste materials, shows great promise for the future.
New Developments in the Field of Vitamin B12: Enzymatic Reactions Dependent upon Corrins and Coenzyme B12
Authors: Schrauzer G. N.
Published: December 2003

Simple corrins such as vitamin B12 and vitamin B12 coenzyme catalyze a variety of unusual enzymatic reactions of which some are still without analogy in organic or organometallic chemistry. The mechanisms of these reactions are currently the subject of lively discussion. The present review focuses attention on new ideas about the mode of action of vitamin B12 coenzymes in enzymatic reactions.
The Biochemistry of Sphingolipid Storage Diseases
Authors: Sandhoff Konrad
Published: December 2003

Sphingolipids are components of animal membranes that are made up of a hydrophobic ceramide and a hydrophilic moiety (phosphorylcholine, oligosaccharides or their derivatives). Several enzymes are required for the step‐by‐step degradation of the sphingolipids. If one of these enzymes is deficient or totally lacking, then its substrates accumulate in the body and cause severe damage, especially when storage occurs in the nervous system. The enzyme defects are inherited in a recessive manner.
Recent Applications of α‐Metalated Isocyanides in Organic Synthesis
Authors: Schöllkopf Ulrich
Published: December 2003

Being both nucleophilic and electrophilic, α‐metalated isocyanides can add to polar double bonds, forming heterocycles. They are also synthons for α‐metalated primary amines. This article describes recent or improved procedures for their use in organic synthesis: (1) In heterocyclic syntheses to give 2‐oxazolines, 2‐imidazolines, 2‐thiazolines, oxazoles and oligooxazoles, thiazoles, triazoles, imidazolinones, pyrroles, 5,6‐dihydro‐1,3‐oxazines and ‐thiazines, and (via cycloaddition with nitrones) 2‐imidazolidinones. (2) In the field of formylaminomethylenation, for example transformation of estrone methyl ether and a keto sugar into the corresponding α‐formylaminoacrylic esters, and the conversion of aldehydes and ketones by 3‐ and 4‐pyridyl‐methyl isocyanides into N‐(1‐pyridyl‐1‐alkenyl)formamides and their hydrolysis to 3‐ and 4‐acylpyridines. (3) In connection with the use of α‐metalated isocyanides as synthons for α‐metalated primary amines, the author demonstrates how they may be used for preparation of 1,2‐ and 1,3‐amino alcohols, 1,2‐diamines, 2,3‐diaminoalkanoic acids and for synthesis of higher amino acids starting from simple amino acids.
Phosphacumulene Ylides and Phosphaallene Ylides [New synthetic methods (19)]
Authors: Bestmann Hans Jürgen
Published: December 2003

Phosphacumulene ylides and phosphaallene ylides are nucleophilic compounds which can add reactants in a variety of ways. Cycloadditions can occur both at the polar C—P ylide bond and at the CC double bond.
Electrophotography
Authors: Weigl John W.
Published: December 2003

Electrophotographic images are formed by the displacement of matter in electric fields: the deposition of charged particles or the deformation of a plastic surface is controlled by a geometric field pattern, configured by the photo‐response of a photoconductive insulating material. Image amplification up to 105may be achieved by the application of external potentials and the judicious selection of imaging particles having a high ratio of absorbance per unit charge. These particles may be ions, colloids, photoresponsive pigments, or (most commonly) colored plastic “toner” composites. Of the many processes which have been invented to date, transfer xerography remains the most useful. This paper presents a concise review of electrophotographic imaging processes and materials, as well as of some of their applications.
(A→D)‐Cyclization of a Nickel(II) Δ18‐Dehydro‐1‐methylidene‐1,19‐secocorrinate
Authors: Rasetti Vittorio , Kräutler Bernhard , Pfaltz Andreas , Eschenmoser Albert
Published: December 2003

Communications are brief preliminary reports of research work in all areas of chemistry which, on account of its fundamental significance, novelty, or general applicability, should be of interest to a broad spectrum of chemists. Authors of communications are requested to state reasons of this kind justifying publication on submission of their manuscript. The same reasons should be clearly apparent from the manuscript. In cases where the editorial staff decide, after due consultation with independent referees, that these conditions are not met, manuscripts will be returned to the authors with the request to submit them for publication in a specialist journal catering for scientists working in the field concerned.
Phenyl‐[2,2‐dimethyl‐1‐(trimethylsiloxy) propylidene]‐arsane, and Arsane with an Isolated AsC Bond
Authors: Becker Gerd , Gutekunst Gerhard
Published: December 2003

The first open‐chain arsane with an isolated AsC double bond, (2), has now been prepared by rearrangement of the pivaloylarsane (1). Compound (1) is obtainable from phenylbis(trimethylsilyl)arsane.
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Synthesis and Properties of Tris(trimethylsilyl)aluminum
Authors: Rösch Lutz
Published: December 2003

The AlSi compound (1) has now been prepared for the first time in about 90% yield. The thermolysis products of (1) suggest the intermediacy of dimethyl‐silanediyl [(CH3)2Si].
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Advances in Phase‐Transfer Catalysis [New synthetic methods (20)]
Authors: Dehmlow Eckehard V.
Published: December 2003

Phase‐transfer catalysis (PTC) has grown into a versatile preparative method in the last few years. The most notable new developments include the use of crown ethers as phase‐transfer catalysts and the introduction of solid‐liquid PTC. Some representative examples have been selected from the large number of new PTC reactions and some of them are summarized in tables.
Molecular States and Molecular Orbitals
Authors: Bock Hans
Published: December 2003

Molecules change their properties on acquisition or loss of energy. The state of a molecule can be characterized by the difference between its energy and that of the preceding initial state or that of the subsequent final state, as well as by the respective charge distribution. Molecules in their various energy states each display a particular structure and characteristic properties, and it is these entities which the chemist uses as synthetic building blocks.—The best model hitherto available for describing molecular states is the molecular orbital representation. Molecular orbitals are especially suitable for comparing mutually corresponding molecular states of similar compounds, and thus provide a manifold and stimulating overview of large areas of chemistry.—An attempt will now be made to point out important characteristic parameters of molecular states and to explain the rules governing their description by molecular orbitals, while circumventing mathematical barriers. A principal objective is the comparison of states of “chemically related” molecules with regard to the connection, the arrangement, and the potential of their atoms. The simple models employed for this purpose, whose inherent limitations and potential expansions are discussed, have meanwhile become valuable tools in the hand of the chemist.
Some Aspects of Antibiotics Research
Authors: Zähner Hans
Published: December 2003

The era of spectacular developments in the field of antibiotics appears to be over. Ever greater efforts are needed to find ever fewer new antibiotics. The view that well‐considered hypotheses can lead as successfully as proven results to further research is supported by the establishment of five theses. “Non‐classical” screening methods and the search for secondary metabolites with unusual properties can provide a rich harvest.
Trifluoromethylamine, CF3NH2
Authors: Klöter Gerhard , Lutz Walter , Seppelt Konrad , Sundermeyer Wolfgang
Published: December 2003

The simplest primary perfluoroalkylamine, CF3NH2, has now been synthesized by two methods. It is rather involatile and has a remarkably high melting point.
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2C‐Chain Elongation of Lithioalkanes with Diphenylvinylarsane and Phenyl Vinyl Selenide
Authors: Kauffmann Thomas , Ahlers Holger , Tilhard Hans‐Joachim , Woltermann Annegret
Published: December 2003

Diphenyl(vinyl)arsane, an electrophilic chain elongation reagent, permits the formal insertion of two CH2 groups into lithioalkanes.
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Bis(trifluoromethyl)disulfane Oxide CF3S(O)SCF3
Authors: Gombler Willy
Published: December 2003

The first disulfane oxide (2) to be stable at room temperature has now been obtained by hydrolysis of the difluoride (1) at −50°C. Numerous dialkyldisulfane oxides are biologically active; all except (2) disproportionate.
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The Te‐O‐Fe System: Te(OTeF5)6
Authors: Lentz Dieter , Pritzkow Hans , Seppelt Konrad
Published: December 2003

The covalent chemistry of tellurium can be developed extensively. In the new Te‐O‐F compound (1), Mr = 1559.2, the large ligands effect perfect occlusion of the central atom.
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Entanglement of Thread Molecules and Its Influence on the Properties of Polymers
Authors: Hoffmann Martin
Published: December 2003

This article shows the extent to which the entanglement of threadlike molecules can influence many of the properties of deformable polymers and of solutions of macromolecular substances. Thus, the molecular concept of entanglement leads to quantitative predictions of the dependence of the entanglement number on the nature of the polymer, its concentration, and extension. Experimental values of the relaxation modulus confirm these predictions for melts and solutions. The influence of entanglemnt on relaxation and flow processes leads to very simple relationships for the magnitudes of the structural viscosity and the shear stress at which the structural viscosity starts to become measurable. Osmotic pressures, light scattering intensities, and diffusion coefficients of concentrated solutions can be derived quantitatively from the conformational constraints due to entanglement. Entanglement is effective above a concentration at which the three‐dimensional coils fill the solution volume, and probably also at lower concentrations. At very high concentrations entangled structures may be formed which drastically reduce the number of possible conformations. The swelling and extension behavior of cross‐linked deformable polymers can be understood only if entanglement is taken into account.
A Stable Acyclic Alkoxyhalosulfurane: Chlorotris(2,2,2‐trifluoro‐1‐trifluoromethylethoxy)sulfurane
Authors: Röschenthaler Gerd‐Volker
Published: December 2003

Alkoxysulfuranes—compounds containing a tetracoordinated sulfur(IV)atom—are important intermediates in synthetic organic chemistry. The first open‐chain chloroalkoxysulfurance has now been prepared. Surprisingly, it is able to alkoxylate
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Comment on the Publication Entitled “Synthesis of a Stable 1,3,4‐Dioxazolidine”
Authors: Zinner Gerwalt , Blass Helmut
Published: December 2003

Comment on the Publication “Synthesis of a Stable 1,3,4‐Dioxazolidine”
Use of Electron‐Density Plots in Applied Quantum Chemistry
Authors: Absar Ilyas , Van Wazer John R.
Published: December 2003

The uses in applied quantum chemistry of computer‐produced three‐dimensional diagrams of electron‐density distributions are discussed. The two major catagories of such diagrams are contrasted; and advantages are described for plots showing as the third dimension the point‐by‐point electron density in a cross‐sectional cut (corresponding to the other two dimensions) through a molecule. Examples are presented to show how these plots may be used (1) to assess the adequacies of a given mathematical representation employed in the calculation of a wavefunction, (2) to clarify the interrelationship between an individual molecular orbital and the atomic orbitals of the constituent atoms, as well as (3) to explain the canonical set of molecular orbitals of any selected molecule. Furthermore these plots serve(4) to demonstrate clearly a replication of key characteristics between certain molecular orbitals in different molecules. These examples are accompanied by others which indicate how the electron‐density plots may be used(5) to understand and clarify accepted chemical dogma. Finally, the possibility is discussed of employing quantum calculations on a wider scale so as to be of value in the more practical aspects of chemistry.
The Co2(CO)8/Ph3P‐Catalyzed Reaction of Aldehydes with Hydrosilane and Carbon Monoxide
Authors: Seki Yoshio , Murai Shinji , Sonoda Noboru
Published: December 2003

Chain elongation of aldehydes with CO to give (protected) enediols (1) is feasible by the reaction shown. In the oxo synthesis, on the other hand, the aldehyde is transformed into formate without CC bond formation.
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Production and Utilization of Amino Acids
Authors: Izumi Yoshiharu , Chibata Ichiro , Itoh Tamio
Published: December 2003

The amino acid industry has been steadily expanding since monosodium glutamate was first marketed as a flavoring material in 1909. Its production has recently reached almost the 1 billion dollar level. Amino acids are produced by extraction from protein hydrolyzates, by fermentation with the aid of microorganisms, by enzymatic processes, and by chemical synthesis. To obtain natural L‐amino acid, chemical synthesis generally requires two additional steps, i.e. optical resolution and racemization of the D isomer. The most important applications of amino acids include the fortification of plant food and feeds by supplementation of the deficient essential amino acid(s). Apart from their uses in the food industry, medical applications of amino acids (nutritional preparations and therapeutic agents) are becoming increasingly important.
The Versatility of Tertiary Phosphane Ligands in Coordination and Organometallic Chemistry
Authors: Mason Ronald , Meek Devon W.
Published: December 2003

Tertiary phosphanes form kinetically stable complexes with formal oxidation states of the metal ranging from + IV to −I (“electronic versatility”). Variously substituted phosphanes and polydentate, chelate forming phosphanes and polyphosphanes can be synthesized (“steric versatility”). Studies on complexes containing such ligands provide, inter alia, useful information about the metal‐phosphorus bond, about the steric effects of the phosphane ligand, and about reactions of coordinated phosphanes.
Reactivity of a Solfonium Ion in Layer Silicates of Montomorillonite Type
Authors: Gosselck Jürgen , Stahl Ingfried
Published: December 2003

Free R3 S+ ions and those intercalated in layer silicates react very differently. While the free S‐benzyltetrahydrothiophenium ion fails to react with arenes, on intercalation in bentonite the ion reacts with benzene, toluene, anisole, chloro‐benzene, etc. to give (o‐and p‐subtituted) aryl(phenyl)methanes. The reaction takes place in the interlamellar space; yields are good.
Chiral Polysiloxanes for Resolution of Optical Antipodes
Authors: Frank Hartmut , Nicholson Graeme J. , Bayer Ernst
Published: December 2003

The imparting of natural enantiomer selectivity to synthetic polymers is a matter of topical interest. A polymeric organosiloxane containing an amino acid as a chiral center has now been synthesized as an “artificial receptor”. This product can be used, inter alia, for enantiomer analysis by gas chromatography, and serves as model for studies on the biological action of enantiomeric substrates.
Ce4O4S3: A Mixed‐Valence Cerium Oxide Sulfide
Authors: Wichelhaus Winfried
Published: December 2003

The first oxide sulfide of rate earth metals to contain M3+ and M4+ ions is CeCeO4S3. The compound is a semiconductor and has M3+ and M4+ in two crystallographically distinct positions.
IR Spectroscopic Detection of Molecular SiO2
Authors: Schnöckel Hansgeorg
Published: December 2003

“True” double bonds between tetravalent silicon and oxygen are present in molecular SiO2, now isolated by a novel matrix technique. This was accomplished by cocondensation of SiO (from a Knudsen cell) and O (generated by microwave excitation) in argon on a cold surface.
Extraction with Supercritical Gases—A Foreword
Authors: Wilke Günther
Published: December 2003

A novel method of separation, extraction with supercritical gases, was the topic of a symposium held at Essen in June of this year. The present issue of Angewandte Chemie International Edition contains all the papers read at this symposium, and thus provides first‐hand information about the state of the art. An industrial plant for decaffeination of green coffee beans with supercritical CO2 will shortly be coming on stream.
Phase Equilibria and Critical Curves of Binary Ammonia–Hydrocarbon Mixtures
Authors: Lentz Harro , Franck Ernst Ulrich
Published: December 2003

Liquid or dense supercritical ammonia has been suggested as an extraction fluid. It is indeed good solvent for very different classes of compounds, as can be seen from phase diagrams. Such diagrams for binary systems of ammonia and hydrocarbons are presented and discussed on the basis of their critical curves. Apparatus and methods for the measurement of phase equilibria and equation of state data of fluid mixtures at high pressure are described.
Deoxygenation—A Novel Reaction Path of Transition Metal‐Substituted Ketenes
Authors: Kreissl Fritz R. , Eberl Karl , Uedelhoven Wolfgang
Published: December 2003

Surprising reactions of carbon monoxide with transition metal complexes have been observed with compounds (1) and (2). The carbyne complex (1) takes up CO at normal pressure and −30°C to form the metalated ketene (2) which itself is deoxygenated by CO at +60°C and under 60atm pressure to form the metalated acetylene (3) (L = P(CH3)3).
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Catalytic Carbon‐Carbon Bond Formation with Carbene Intermediates
Authors: Henrici‐Olivé Gisela , Olivé Salvador
Published: December 2003

The transformation of methylamine into acetonitrile is catalyzed, e. g. by Moon SiO2. On admixture of hydrogen (H2:CH3NH2 = 12:1) 20–30% of the methylamine are converted into the C2 product. The reaction proceeds via an intermediate of the type H2CM.
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2,2′‐Bipyridine(tetramethylcyclobutadiene)nickel(0)
Authors: Griebsch Udo , Hoberg Heinz
Published: December 2003

The first monocyclobutadiene‐nickel(0) complex, the bipyridine‐stablized tetramethyl derivative (2), has been prepared from the nickel(II) complex (1). Compound (2) is diamagnetic, of remarkable thermal stability, sublimable in a vacuum, and hydrogenated only with difficulty.
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Redox Properties of Zinc Tetrabenzporphyrin
Authors: Vogler Arnd , Rethwisch Birgit , Kunkely Horst , Hüttermann Jürgen , Besenhard Jürgen Otto
Published: December 2003

The redox potential of porphyrins could previously only be modified by variation of the central metal and additional axial ligands. However, it can also be considerably reduced by extension of the π‐electron system of the porphyrins: in zinc tetrabenzporphyrin (containing a redox‐inert metal) the potential difference between the first oxidation and the first reduction of the ring is only 1.84 V, as against ca. 2.25V in other porphyrins.
Coordination Number 3 in CoII: Na10[Co4O9], an Oligooxocobaltate(II)
Authors: Burow Wilfried , Hoppe Rudolf
Published: December 2003

The first compound of cobalt in a trigonal‐planar environment, viz. Na10[Co4O9] has been obtained in the form of red single crystals by annealing of Na2O and “active” CoO in sealed cobalt tubes. The oxide is extremely sensitive to moisture, and also consitutes the first oxocobaltate(II).
Xe(OTeF5)6, A Deep‐Colored Noble Gas Compound, and OXe(OTeF5)4—The Existence of Kr(OTeF5)2
Authors: Lentz Dieter , Seppelt Konrad
Published: December 2003

The red‐violet color of Xe(OTeF5)6 (1) must be attributed to the bonding state of hexavalent xenon which possesses a nonbonding electron pair: Te(OTeF5)6 has no such pair and is colorless. The extremely light‐sensitive compound (1) probably exists as a monomeric molecule with covalent bonds.
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Activation Analysis—Its Present State of Development and Its Importance as an Analytical Tool
Authors: Krivan Viliam
Published: December 2003

Activation analysis is one of the most important methods available for the determination of traces of elements and of isotopes. One special advantage of activation analysis is its ability to cope with the simultaneous determination of many elements with very high detection sensitivity–for many elements lying below the ppb level. In some cases as little as 10−14—10−15g of an element can be detected. A number of sources of systematic errors common to other analytical procedures, mainly those caused by the blank, are eliminated in activation methods. The disadvantages may be seen as the inconvenience of handling radioactive materials, the dependence on large irradiation facilities, and sometimes the unavoidably long irradiation and cooling periods. On account of its unique capabilities activation analysis finds applications in all fields of endeavor where minute amounts of elements are of significance, from materials research through medicine to archaeology. Further improvements in performance and increases in scope are seen to lie in the development of new radiation sources, activation techniques, measurement systems, and separation procedures.