bluuebunny/crossref_metadata_2025 huggingface dataset:
Fulvenes as Isomers of Benzenoid Compounds
Authors: Hafner K. , Häfner K. H. , König C. , Kreuder M. , Ploss G. , Schulz G. , Sturm E. , Vöpel K. H.
Published: December 2003

With regard to the nature of their bonding and reactivity, fulvenes occupy a position intermediate between their benzenoid isomers and the olefins. The chemical and physical behavior of the fulvenes is determined either by the diene character of the cross‐conjugated system or by the cylic conjugation in the five‐membered ring, depending on the type of substituent at the exocyclic carbon atom. In addtion to several new substitution reactions, a description is given of the syntheses and reactions of 6‐amino‐ and 6‐hydroxyfulvenes, isomeric with anilines and phenols, the derivatives of which can be used for the preparation of new types of nonbenzenoid cyclic conjugated systems such as carbocyclic and heterocyclic azulenes, pseudoazulenes, thiepines, dihydropyridazines, and s‐indacene.
Syntheses Using Pyridinium Salts
Authors: Kröhnke Fritz
Published: December 2003

This review discusses syntheses leading to a new type of N‐vinylpyridinium salts, to novel anionocyanines, to aminophenazines and alloxazines, as well as to (aza‐) dehydroquinolizinium, acridizinium, and morphanthridizinium salts. In addition, Mannich reactions and aminoalkylations at active methylene groups of cycloimmonium salts, and their reactions with amines are treated. The possibilities offered by the “Ortoleva‐King” reaction are demonstrated using numerous examples, such as a new route leading to the yohimbine skeleton.
Inorganic Reactions with Arc‐heated Gases
Authors: Harnisch H. , Heymer G. , Schallus E.
Published: December 2003

A novel electric‐arc device, with a torch consuming 100to 240 amps DC has been developed. In previous apparatus of this kind, both reactants passed through the arc together, but now only one component (e.g., hydrogen or nitrogen) is heated in this new‐process. The temperature of this component is raised to a point where it exists in a highly excited state or dissociates into free atoms and then leaves the arc in a stream with supersonic velocity through a hole drilled in the anode, being then mixed with the other reactant. The resultant mixture is then immediately quenched. The design and operation of the torch as well as the mixing and quenching procedures are discussed. The preparation of chlorosilanes, titanium trichloride, titanium nitride, and hydrazine by this method is described.
The Biogenesis of Ergot Alkaloids
Authors: Weygand F. , Floss H.‐G.
Published: December 2003

In this article the biogenesis of the ergoline ring in lysergic acid derivatives and the clavines is discussed. T·yptophan and mevalonic acid are the precursors. The N‐methyl group is supplied by formate or methionine. Concepts and results dealing with the manner in which the compounds are formed are discussed. Finally, the known biogenetic relationships among the ergot alkaloids are discussed in connection with their biogenesis.
Solid‐State Reactions
Authors: Schmalzried H.
Published: December 2003

In the following, solid‐state reactions between ionic crystals are described. The vast field of powder reactions will not be discussed, since various parameters such as particle size distribution and packing density are difficult to determine exactly. The result of this is, that it is almost impossible to establish the mechanisms of solid‐state powder reactions unambiguously and derive general expressions for reaction rates.
The Mössbauer Effect and its Significance in Chemistry
Authors: Fluck E. , Kerler W. , Neuwirth W.
Published: December 2003

Resonance fluorescence of recoil‐free γ‐rays from atomic nuclei depends on the state of the chemical bonding of the atoms. The latter influences the position of the energy level of the atomic nuclei, so that the energy required for excitation of resonance fluorescence is somewhat smaller or greater than the energy of the γ‐quanta emitted by the radiation source. In order to obtain resonance fluorescence, therefore, the radiation source and absorber have to be kept moving relative to each other. If the intensity of the resonance fluorescence is plotted against this relative velocity, Mössbauer spectra are obtained. The positions of the lines in these spectra make it possible to draw conclusions about the nature of the atom's bonds. The efficiency of this method is demonstrated by illustration with numerous iron compounds. It was shown, for instance, that the iron atoms in “insoluble Prussian Blue” have well‐defined oxidation levels. “Turnbull's Blue” shows the identical spectrum. A structure could be ascribed to tri‐iron dodecacarbonyl that also explains the diamagnetism of the compound.
Methods of Peptide Synthesis
Authors: Wieland T. , Determann H.
Published: December 2003

In the series of accounts of progress in the field of peptide synthesis, this review surveys the literature from the beginning of 1959 to the middle of 1962.
Base‐Catalysed Reactions of Ketones with Hydrogen Sulfide
Authors: Mayer Roland , Hiller G. , Nitzschke Margot , Jentzsch J.
Published: December 2003

Monoketones react with hydrogen sulfide in the presence of basic catalysts to give geminal dithiols or thioketones. β‐Diketones are converted into monothiodiketones. α‐Diketones can be selectively reduced by hydrogen sulfide in the cold in the presence of secondary or tertiary amines to give hydroxy‐or mono‐ketones.
Recent Studies on the Centrally Active Endogenous Amines
Authors: Daly J. W. , Witkop B.
Published: December 2003

The past five years have withnessed significant progress in our knowledge of the metabolism and importance of endogenous, peripherally and centrally active amines. Most of the modern drugs which influence human mood, emotion, or temperament do so by their direct or indirect effect on the biosynthesis, metabolism, storage, or release of endogenous amines in the brain. The relationships discovered in this connection have deepened our understanding of the biochemical basis of acute, chronic, and hereditary mental disorders. The beginnings of a new science “psychochemistry” are discernible at this point.
Syntheses of Heterocyclic Compounds from Aminoguanidine
Authors: Kurzer F. , Godfrey L. E. A.
Published: December 2003

Due to its unique structure, aminoguanidine is capable of reacting as a derivative of hydrazine, guanidine or formamidine. Addition and condensation reactions yield products which can be cyclized to heterocyclic compounds. Frequently, heterocyclics are directly accessible from aminoguanidine in one stage.
Modern Methods for the Separation and Continuous Measurement in the Gas Phase of Compounds Labelled with Radiocarbon. Radio and Reaction Gas Chromatography
Authors: Drawert F. , Bachmann O.
Published: December 2003

In biochemical work with isotopic tracers, it is frequently advantageous to investigate samples in the gas phase. In this way, the selectivity of gas‐chromatographic separating columns and the sensitivity of detectors can be utilized for both the detection of gas‐chromatographic fractions and the determination of their radioactive portions. Conversion of materials separated by gas chromatography into a single standard chemical compound prior to measurement of the radioactivity is recommended. Methods suitable for 14C‐labelled compounds can also be applied to those labelled with 3H or 35S.
1,3‐Dipolar Cycloadditions. Past and Future
Authors: Huisgen Rolf
Published: December 2003

In contrast to the very large number of special methods applicable to syntheses in the heterocyclic series, relatively few general methods are available. The 1,3‐dipolar addition offers a remarkably wide range of utility in the synthesis of five‐membered heterocycles. Here the “1,3‐dipole”, which can only be represented by zwitterionic octet resonance structures, combines in a cycloaddition with a multiple bond system – the “dipolarophile” – to form an uncharged five‐membered ring. Although numerous individual examples of this reaction were known, some even back in the nineteenth century, fruitful development of this synthetic principle has been achieved only in recent years.
Nitrenes
Authors: Horner L. , Christmann A.
Published: December 2003

Nitrens are molecular fragments with six electrons on the nitrogen which are formed thermally or photochemically from hydrazoic acid or organic azides. Kinetics of the cleavage of azides, spectroscopic data, and electron spin resonance measurements constitute proof for a biradical nature of the nitrens studied. As a result of hydrogen shifts, nitrens are capable of isomerization to mines, of hydrogen abstraction from neighbouring molecules affording primary amines, and of ring formation by internal dehydrogenation (insertion reactions). Isomerization and hydrogen shifts are observed primarily with alkylnitrens; however, under favorable structural conditions, hydrogen shifts in arylnitrenes also lead to immines. Arylinitrens dimirize to azo compounds and undergo intra‐ and intermolecular reactions with nucleophilic reactants. Thus, both stable and unstable acylnitrenes, which are formed thermally or photolytically from acyl azides, add on, for example, to dimethyl sulfide or dimethyl sulfoxide, affording sulfimines or sulfoximines, respectively. Nucleophilic reagents, such as alcohols and amines, also react with nitrenes. Besides azides, anil‐N‐oxides also undergo cleavage to give nitrenes. The reaction of N‐chloramines and hydroxylamine‐O‐sulfonic acids with nucleophilic reagents probably does not proceed via a nitrene intermediate, but rathr by an SN mechanism. A crucial experiment differentiating between these two paths is described, and Rashig's hydrazine synthesis is discussed in detail.
An Acylal of Dimethylketene
Authors: Bestian H. , Günther D.
Published: December 2003

Free dimethylketene is difficult to handle because of its tendancy to dimerize even at low temperatures and to from explosive peroxides with atmospheric oxygen. In contrast, the dimethylketenacylal of dimethylmalonic acid is simple and safe to use. This compound affords dimethylketene on thermal or catayltic cleavege, hence, it can replace the free ketene in nearly all reaction. The synthesis and reactions of this acylal are described.
Isothiazoles
Authors: Hübenett F. , Flock F. H. , Hansel W. , Heinze H. , Hofmann Hd.
Published: December 2003

The ring system of non‐anellated 1,2‐thiazoles (isothiazoles) has only recently become accessible. Four syntheses and numerous interconversions have opened up new routes to compounds which command interest as intermediates and as analogues of natural products and established pharmaceuticals.
Type and Extent of Isomerization of Straight‐Chain Mono‐olefins during the Koch Carboxylic Acid Synthesis
Authors: Möller K. E.
Published: December 2003

When straight‐chain mono‐olefins, from pentene to decene, are subjected to the Koch carboxylic acid synthesis by the addition of CO and H2O or CH3OH in the presence of strongly acidic catalysts, not only the expected secondary acids, but also mixtures of a specific type of tertiary acids or their methyl esters are formed. When the catalysts contain boron trifluoride, the secondary acids are formed in ratios of isomers which are, within the scope of this investigation, independent of the experimental conditions and which agree well with the values calculated from the isomer equilibria of the corresponding n‐olefins. Using concentrated sulfuric acid as catalyst, a larger proportion of tertiary acids is obtained than with BF3‐catalysis, and amongst the secondary acids, those isomers predominate in which the COOH group is situated near the centre of the molecule.
Phenol Oxidation Reactions
Authors: Musso H.
Published: December 2003

The use of well‐known phenol oxidation reactions for the preparation of compounds arising from CC and CO coupling has recently received increased attention. A selection from the large number of products obtainable by oxidation of mono‐ and polyhydric phenols and a discussion of the reaction mechanisms indicate the scope of this method. The formation of hydroxyphenylquinones and orceine dyes from resorcinol derivatives is explained. The synthesis of natural products by way of phenol oxidations is briefly discussed.
The Reaction of Oxides with Water at High Pressures and Temperatures
Authors: Wendlandt H. G. , Glemser O.
Published: December 2003

The reactions of the oxides SiO2, MoO3, and WO3 with steam at temperatures between 400 and 700 °C and pressures of 5 to 500 atm were studied by means of the transfer method. The results were evaluated by a new method. In the system Sio2/H2O the formation of gaseous Si(OH)4, Si2O(OH)6, and [SiO2(OH)2]x was found to occur in three different water‐density ranges. In the systems MoO3/H2O and WO3/H2O the gaseous compounds MoO2(OH)2 and WO2(OH)2, which were already known, exist up to densities of approximately 0.05g/cm3. At higher densities, at which the supercritical phase begins to show the properties of a liquid to an ever increasing extent, isopolymolybdic or isopolytungstic acids appear.
Defensive Substances of the Arthropods, Their Isolation and Identification
Authors: Schildknecht H. , Holoubek K. , Weis K. H. , Krämer H.
Published: December 2003

Numerous orders of arthropods have organs which produce and store defensive substances. The purpose of our studies was to learn more about the chemical composition of these defensive secretions. In this work, we had to forego a priori many of the possibilities of classical organic‐chemical analysis, since some of the insects were difficult to obtain and operation with substantial amounts of material was precluded. However, the defensive substances of various families of Arthropoda were characterized by using modern chemical and physical analytical procedures and our own methods of separation, purification, and enrichment which we developed specifically for this purpose.
The Mechanism of the Action of Organometallic Catalysts
Authors: Sinn H. , Patat F.
Published: December 2003

Kinetic investigations of the polyreaction of isoprene with organolithium compounds as initiators in n‐heptane as solvent indicate the following sequence of reactions: 1. formation of an adduct between a monomeric form of the organolithium compound and the isoprene and 2. reaction of this adduct with an associated form of the organolithium compound with insertion of the isoprene. The adduct formation is considered to be due to chemisorption, and proof of such chemisorption of a monomer (ethylene) is also demonstrated for a homogeneous Ziegler‐type catalyst. All the reactions can be formulated in the form of cyclic structures with electron‐deficient character. Postulation of such ring structures explains the surprising values obtained for the frequency factors and equilibrium constants.
Transformations of Organoboranes at Elevated Temperatures
Authors: Köster R.
Published: December 2003

Trialkylboranes with identical or different groups on the boron are stable to alkyl exchange at room temperature. Mixed trialkylboranes only undergo disproportionation in the presence of catalysts such as aluminum trialkyls and boron‐hydrogen compounds. At temperatures above 100 °C, organoboranes such as trialkylboranes and B‐alkylboracyclanes isomerize as a result of migration of the boron along the aliphatic hydrocarbon radical via dehydroboration‐hydroboration equilibria. Alkyl, cycloalkyl, as well as aralkyl and certain arylboranes can be converted irreversibly by pyrolysis at 200–300 °C into other organoboranes (methylboranes and boron‐heterocycles of various structures).
Oxidative Condensation of Quaternary Phenolic Bases
Authors: Franck B. , Blaschke G. , Schlingloff G.
Published: December 2003

Provided they contain quaternary nitrogen, simple phenolic bases can undergo oxidative condensation under conditions similar to those of biogenesis to form alkaloids of the isoquinoline series with good yields. By means of such oxidative condensations, more than sixty alkaloids of various structural types have become more easily obtainable. Of the numerous possible condensations of the intermediate mesomeric radicals only those which lead to naturally occurring alkaloids give good yields and few by‐products. The results suggest that oxidative condensations of quaternary bases are also involved in the biosynthesis of alkaloids in the plant cell.
New Methods of Preparative Organic Chemistry IV. Cyclization of Dialdehydes with Nitromethane
Authors: Lichtenthaler F. W.
Published: December 2003

Condensation of nitromethane with suitable diadehydes in alkaline medium provides a general method of cyclization, in which the methyl group of the nitromethane is incorporated into the ring. This method leads to 5‐, 6‐, and 7‐membered rings and is equally applicable to aliphatic, aromatic, and sugar dialdehydes. For example, glyoxal is converted into 1,4‐dideoxy‐1,4‐dinitro‐neo‐inositol, and glutaraldehyde into trans‐2‐nitrocyclohexane‐1,3‐diol, while the corresponding cyclization of xylo‐trihydroxyglutaraldehyde leads to deoxy‐nitroinositols having the scyllo, myo‐1, and muco‐3 configurations.‐In the case of aromatic dialdehydes, the cyclization is accompanied by elimination of water. Thus, phthalaldehyde, naphthalene‐2,3‐dicarboxaldehyde, and homophthalaldehyde yield, respectively, 2‐nitroindenol, 2‐nitrobenzindenol, and 2‐nitronaphthalene. ‐Application of the method to sugar dialdehydes (aldehydic diglycol derivatives of monosaccharides formed by periodate oxidation) constitutes an excellent synthesis of 3‐amino sugars, since 3‐deoxy‐3‐nitropyranoses are formed smoothly on cyclization, and the corresponding 3‐amino derivatives are obtained by hydrogenation. Thus, the reaction sequence: periodate oxidation → cyclization with nitromethane → hydrogenation, leads in the case of α‐and β‐D‐pentosides to 3‐amino‐3‐deoxy‐D‐and‐L‐pentosides, respectively, with ribo, xylo, and arabino configurations. α‐D‐hexosides give derivatives with gluco, manno, and galacto configurations. 3‐Amino‐3,6‐dideoxyglucosides of the D‐and L‐series are obtained from 6‐deoxy‐D‐or‐L‐hexosides, respectively, and 3‐aminohexosans with gulo, ido, and altro configurations are obtained from 1,6‐anhydro sugars. Cyclization of the dialdehydes obtained from sedoheptulose and methyl 4,6‐O‐ethylidene‐α‐D‐glucoside by periodate oxidation, leads to 3‐nitro and, after hydrogenation, to 3‐amino derivatives of 3‐deoxyheptopyranoses.
Synthesis of Naturally Occurring Unsaturated Fatty Acids by Sterically Controlled Carbonyl Olefination
Authors: Bergelson L. D. , Shemyakin M. M.
Published: December 2003

It is shown that carbonyl olefination, i.e. the reaction of carbonyl compounds with alkylidene phosphoranes, can be sterically controlled. In some cases cis‐olefins can be obtained by proper choice of the reaction conditions; trans‐olefins are formed only in the presence of suitable structural factors. These cis‐and trans‐olefination reactions have opened new, stereo‐specific routes to unsaturated and polyunsaturated fatty acids with differing positions and sequences of cis‐ and trans‐double bonds and to ω‐hydroxy and branched chain fatty acids.
New Methods of Preparative Organic Chemistry IV
Authors: Wanzlick H. W. , Lehmann‐Horchler M. , Mohrmann S. , Gritzky R. , Heidepriem H. , Pankow B.
Published: December 2003

If catechol or other hydroquinones are dehydrogenated in the presence of a nucleophilic reagent, the latter reacts, usually by Michael addition, with the quinone formed in situ. The wide range of possible variations offered by this synthetic method is comprehensively described in the present paper. procedures are given for carrying out typical reactions.
New Reactive Dyes
Authors: Kleb K. G. , Siegel E. , Sasse K.
Published: December 2003

Two new groups of reactive dyestuffs have been developed. One group (Levafix® dyes) comprises compounds which contain SO2NHCH2CH2OSO3H or CH2N(alkyl)‐CH2CH2OSO3H as reactive groups. The dyes of this group react with cellulose fibers to form cellulose ethers, e.g. RSO2NHCH2CH2Ocellulose. The substances in the second group (Levafix‐E® dyes) consist of the amides formed from 2,3‐dichloroquinoxaline‐6‐carboxylic acid and dyestuffs containing primary or secondary amino groups.
Relations between Structure and Reactivity of Ambifunctional Nucleophilic Compounds
Authors: Gompper R.
Published: December 2003

Theoretical considerations and recent experimental results have added greatly to our knowledge of the structures and reactivities of ambifunctional nucleophilic compounds during the last few years. In the present work an attempt is made to present a survey of the theories which have been developed to explain the behavior of these compounds towards electrophilic reagents, and to formulate rules which may serve as guides for carrying out new reactions.
Surface Oxides of Carbon
Authors: Boehm H.‐P. , Diehl E. , Heck W. , Sappok R.
Published: December 2003

On oxidation of graphitic carbon, acidic surface oxides (or hydroxides in the presence of water) are formed at the boundaries of the carbon layers. It was found that the reaction of oxygen with microcrystalline carbon at 400–450°C yields four groups of different acidities. One strongly acidic group and one weakly acidic carboxyl group have been detected, as well as a phenolic hydroxyl group; a carbonyl group is probably also present. With dissolved oxidizing agents, one equivalent of another strongly acidic carboxyl group is formed in addition at room temperature. The possible constitutions of the acidic surface oxides are discussed. Chemically detectable surface oxides are also formed on the surface of diamond. In the presence of oxygen at 800–900°C under reduced pressure, diamond is transformed into black carbon. Surface oxides play a part in this transformation.
Stereospecific Homopolymerization of Cyclopentene
Authors: Natta G. , Dall'Asta G. , Mazzanti G.
Published: December 2003

The polymerization of cyclo‐olefins, like that of olefins with an internal double bond, is sterically hindered. Within recent years it has become possible to prepare copolymers of these compounds with ethylene, with the aid of anionic coordination Ziegler catalysts. This copolymerization always results in cis‐opening of the double bond. Despite the steric hindrance, cyclobutene and cyclopropene have also been homopolymerized, with opening of the double bond. – Rather surprisingly, the best catalysts for homopolymerization of cyclopentene are those which exhibit low activity in the polymerization of ethylene. Ring cleavage occurs with MoCl5/Al(C2H5)3 to give the cis‐polypentenamer, whereas WCl6/Al(C2H5)3 gives the trans‐polypentenamer. Both polypentenamers exhibit elastomeric properties. – Evidence from infrared spectra and oxidative degradation indicates that the monomer units in the trans‐polypentenamer are linked head‐to‐tail. It is presumably the single bond adjacent to the double bond that is broken. Using X‐ray methods at −50 °C, it was possible to determine the crystal structure of the crystalline trans‐polypentenamer at about 400% elongation.
Phosphonium Salt Formation of the Second Kind
Authors: Hoffmann H. , Diehr H. J.
Published: December 2003

Organic compounds containing a positively polarized halogen atom react with tertiary phosphines either with reductive elimination of the halogen or with formation of phosphonium salts and quasi‐phosphonium salts, depending on the solvent. In this reaction, the phosphine first attacks the halogen.
Proton‐Addition Complexes of Aromatic Hydrocarbons
Authors: Perkampus H.‐H. , Baumgarten E.
Published: December 2003

The structures of proton‐addition complexes of aromatic hydrocarbons were hitherto known only with respect to their stoichiometric compositions but can now be clarified by ultraviolet, infrared, and NMR spectroscopic methods. For example, it has been possible to prove by NMR soectroscopy that the expected addition of protons into 9,10‐dimethyl‐[a] benzanthracene actually does take place. Two isomeric proton adducts of toluene have been found by means of infrared spectra. On addition of protons, the ultraviolet spectra of aromatics change considerably; excellent agreement is sometimes observed between the band maxima calculated by quantum mechanics and those found by experiment.
Cyclopropenylium Compounds and Cyclopropenones
Authors: Krebs A. W.
Published: December 2003

The predictions of Hückel's rule gave the incentive to numerous investigations which led ultimately to a new definition of aromatic character, and which have added greatly to our knowledge of the properties and reactivity of aromatic compounds. Increasing use was made of physical measurements as criteria for the aromaticity of a compound. The first member (n = O) in the series of Hückel's (4n + 2) π systems is the cyclopropenylium cation. The predictions regarding the stability of this system have been confirmed at least qualitatively by the synthesis of cyclopropenylium salts. Properties and reactions of cyclopropenylium compounds and cyclopropenones were investigated.
Empirical Parameters of the Polarity of Solvents
Authors: Reichardt C.
Published: December 2003

The empirical parameters of the polarity of solvents which have been determined recently are reviewed: Y‐values (Winstein, Grunwald), X‐values (Gielen, Nasielski), Ω‐values (Berson, Hamlet, Mueller), Z‐values (Kosower), ET‐values (Dimroth, Reichardt, Siepmann, Bohlmann), R‐ and S‐values (Brownstein). Their field of application and interrelationships are discussed. The theoretical principles of the solvent effect on the reaction rate and light absorption of organic compounds are briefly described, and mention is made of attempts to correlate the physical characteristics of the solvent with the empirical parameters.
Cyclic Compounds as Configurational Models for Stereoregular Polymers
Authors: Farina M. , Peraldo M. , Natta G.
Published: December 2003

It is possible to draw analogies between linear polymers and cyclic compounds. Stereochemical considerations developed in this connection led to the recognition of new aspects of importance for the systematic classification of both classes of compounds; for example, asymmetric structures can be predicted which had hitherto never been suspected. – The concept of “diasteric centers” is introduced, and the definition of an “asymmetric center” is expressed in more general terms.
New Methods in the Chemistry Pyridazones
Authors: Dury K.
Published: December 2003

A new synthesis of mucochloric acid by chlorination of butynediol has facilitated the preparation of a series of 4,5‐dichoropyridazones. The high reactivity of these compounds has been investigated and applied in several ways. New classes of compounds, some with biological activity, were obtained by displacement of the chlorine atoms. New heterocyclic systems were prepared by condensation and rearrangement reactions.
The Chemistry of Vinylsulfonic Acid
Authors: Distler H.
Published: December 2003

Vinylsulfonic acid and its derivatives can be prepared from β‐chloroethanesulfonyl chloride or carbyl sulfate (β‐hydroxysulfonyloxyethanesulfonic anhydride). The chemistry of vinylsulfonic acid has assumed industrial importance since the discovery of a simple synthesis of β‐chloroethanesulfonyl chloride from chloroethane or ethane, sulfur dioxide, and chlorine by the Reed process. Carbyl sulfate is as important a starting material as β‐chloroethanesulfonyl chloride, and surpasses the latter in some respects, e.g. on account of the low price of its components ethylene and sulfur trioxide. Vinylsulfonates undergo addition reactions with alcohols, phenols, thiols, sulfinic acids, carboxylic acids, amides, imides, and hydrazides, as well as with amines, ureas, diazonium salts, and nitroparaffins. Furthermore, they undergo halogenation, nitration, olefination, and the Diels‐Adler reaction. – Methods for the preparation of the free vinylsulfonic acid are described. Alkyl vinylsulfonates are excellent alkylating agents. The derivatives of vinylsulfonic acid are used e.g. as plasticizers, emulsifiers, and fungicides.
Formation of Free Radicals in Polyamide Fibers during Drawing
Authors: Matthies P. , Schlag J. , Schwartz E.
Published: December 2003

The formation of free radicals during the process of drawing of spun fibers was observed for the first time with two polyoxamides. The fibers turn red, and an ESR signal can be detected. Both, color and ESR absorption are not permanent. The decrease in the intensity of the ESR absorption and the change in the optical reflectance with time, as well as the dependence of the decoloration on temperature were investigated. The action of high‐energy radiation on the polyoxamides also leads to a red coloration and gives rise to ESR signals. It is concluded that the red color is due to free radicals associated with the oxamido group.
The Function of the promotors in the Technical Ammonia Catalyst
Authors: Krabetz R. , Peters Cl.
Published: December 2003

An attempt is made to give a phenomenological description of the relationships between the catalytic activity and the distribution of the promotors in the reduced ammonia catalyst. Investigations were carried out on series of catalysts whose compositions were gradually brought closer to that of technical ammonia catalysts by the addition to iron of one new activator (Al2O3, K2O, CaO, MgO, SiO2) at a time.
New Finding in the Chemistry of the Lower Oxides of Sulfur
Authors: Schenk P. W. , Steudel R.
Published: December 2003

Important advances have recently been made in the chemisty of the lower oxides of sulfur, both in the preparative sphere and by the application of modern physical methods of investigation. In this paper the knowledge gained to date on the compounds SO, S2O2, S2O, S2O3, and the polysulfur oxides is reviewed and critically appraised.
The Prostaglandins
Authors: Samuelsson B.
Published: December 2003

Prostaglandins occur in many animal species and tissues. They are C20‐carboxylic acids contining one five‐membered ring, one keto group, two or three hydroxy groups, and one to three CC double bonds. Their structures were elucidated by chemical, radiochemical, and physical methods in combination with gas chromatography and mass spectrometry. The prostaglandins are biosynthesized from essential fatty acids. By their action smooth muscles are stimulated and lipid metabolism is affected.
Isonitrile Syntheses
Authors: Ugi I. , Fetzer U. , Eholzer U. , Knupfer H. , Offermann K.
Published: December 2003

In spite of the large number of reactions which involve the formation of isonitriles, the only preparative routes to these compounds, until recently, were the classical isonitrile syntheses discovered about one hundred years ago by Gautier and Hofmann. These methods are not generally applicable, and give satisfactory yields only in exceptional cases. Isonitriles have recently become readily available by the elimination of water from N‐substituted formamides, using acyl halides of Group IV–;VI elements in the presence of bases as dehydrating agents. A dehydrating system with a particularly wide range of application consists of phosgene with tertiary amines. This system generally provides the easiest and most productive route to isonitriles, particularly where large quantities (> 1 mole) are to be prepared.
Chemistry and Stereochemistry of Fluorophosphoranes
Authors: Schmutzler R.
Published: December 2003

Flurophosphoranes are a recently discovered new type of phosphorus compound derived from phosphorous pentafluoride by substitution of fluorine atoms with various groups. Synthesis, chemistry, and stereochemistry of this class of compounds containing phosphorus in the comparatively rare coordination number 5 will be discussed.
The Structure of Sugar Phenylosazones
Authors: Mester L.
Published: December 2003

The open‐chain chelate structure of sugar osazones, first proposed by Fieser and Fieser, has now been confirmed by chemical methods, X‐ray analysis, and NMR spectroscopy. These investigations showed that the properties of sugar osazones are best described by a formula containing a quasi‐aromatic chelate ring.
Melting and Crystal Structure — Some Current Problems
Authors: Ubbelohde A. R.
Published: December 2003

The “classical” definition of liquid and solid phases acording to mechanical criteria is unsatisfactory. It is now know that “premelting” effects occur in crystals, and in many liquids the formation of clusters is observed near the melting point, with structures which can correspond to the short‐range order of the crystals from which the melt is derived.–In particular, the implications of the theories of Lennard‐Jones and Devonshire and of Mizushima and Ookawa are discussed.
Valence‐Bond Isomers of Aromatic Systems
Authors: van Tamelen E. E.
Published: December 2003

The prefix xn is proposed for the classification of valence‐bond isomers of aromatic systems, where n is the change in the number of rings or in the number of π‐bonds on isomerization. Representatives of the x1‐series are Dewar benzene and 9, 10‐dihydronaphthalene. Benzvalene and prismane belong to the x2 and x3 series, respectively. Various derivatives of such valence‐bond isomers have recently become known.
Valence‐Bond Isomers of Substituted Benzenes
Authors: Viehe H. G.
Published: December 2003

Dewar benzene, Ladenburg benzene (prismane), and a combination of these bond systems (benzvalene) have variously been discussed as planar limiting structures of benzene, although they have no physical reality. If, however, we regard these systems as non‐planar structures (as did their originators), they become chemical individuals, derivatives of which have recently been isolated. In addition to being a valance‐bond isomer of benzene, benzvalene is also the first member of a still largely hypothetical series of molecules (the valenes), in which the skeleton atoms can change places with their neighbors to produce the valencebond isomers. The best‐known representative of this class is bullvalene.
On the Analysis of Photosynthesis by Flashlight Techniques
Authors: Witt H. T. , Rumberg B. , Schmidt‐Mende P. , Siggel U. , Skerra B. , Vater J. , Weikard J.
Published: December 2003

Direct information regarding the primary process in photosynthesis is obtained by measurement of the very short‐lived primary and intermediate products with the aid of (1) flash photometry, (2) periodic flash photometry, and (3) flash manometry. The analysis of the primary process using these methods on normal plant cells and chloroplasts and on those which have been chemically or physically modified has led to the formulation of a reaction scheme for the transport of electrons in photosynthesis.
Structure Determination of Free Molecules by Electron Diffraction
Authors: Almenningen A. , Bastiansen O. , Haaland A. , Seip H. M.
Published: December 2003

The intensity of electrons scattered by a gas can be calculated with classical as well as with quantum‐mechanical methods. The range of validity of the equations obtained can be found experimentally. Comparison of the calculated and empirical intensity or radial distribution curves allows the determination of the structure and amplitudes of vibration of a molecul. – For example, it has been found that the two bromine atoms in cis‐1, 3‐dibromocyclobutane occupy equatorial positions. The benzene rings in biphenyl derivatives are inclined at about 45° to each other. In biscyclopentadienylberyllium, the metal atom is not located midway between the two rings.
Chemistry and Biochemistry of α‐Lipoic Acid
Authors: Schmidt Ulrich , Grafen P. , Goedde H. W.
Published: December 2003

The principal physiological function of lipoic acid appears to be its action as coenzyme in the oxidative decarboxylation of α‐oxo acids. In order to find out whether lipoic acid is essential to higher organisms, structurally modified lipoic acids were prepared as potential antagonists. Only 4‐oxalipoamide promotes the growth of S. faecalis 8043; the other substances tested are inactive or else inhibit growth. In experiments to determine the substrate specificity of lipoamide oxidoreductase and its inhibition by structurally modified lipoic acids, no strong inhibitors were discovered. –; Ring strain, spectra, and ring cleavage of compounds containing the 1, 2‐dithiolane ring are discussed in relation to the biological function and the reactivity of lipoic acid.
Extreme Values of the Pressure Coefficient of Viscosity
Authors: Kuss E.
Published: December 2003

The pressure coefficients of viscosity of hydrocarbons and ethers containing two to four phenyl groups linked either directly, via methylene bridges, or via CH(CH3) bridges, were studied with a view to elucidating the reason for the extreme viscosity‐pressure behavior of certain mineral oils. Measurements were made in the range of 1 to 2000 atm at 25, 40, 60, and 80 °C. The results show the existence of a simple relationship between molecular structure and viscosity‐pressure coefficient, and suggest applications in control engineering and lubrication technology.
A Method for the Preparation of Methylmetal Compounds
Authors: Sundermeyer W. , Verbeek W.
Published: December 2003

A new method has been developed for the preparation of methylmetal compounds from methyl chloride and the chlorides of boron, aluminum, silicon, tin, phosphorus, antimony, or mercury. Fused salts are used as solvents, and metals are suspended in these to act as halogen acceptors. The metals are recovered, together with chlorine, by electrolysis. This process, which can be carried out continuously and quantitatively, can be used for the preparation of technically important methylmetal compounds that cannot be obtained directly by the “Mülheim aluminum alkyl method”.
The Separation of Zirconium and Hafnium by Liquid‐Liquid Partition of their Thiocyanates
Authors: Fischer Werner , Deierling B. , Heitsch H. , Otto G. , Pohlmann H.‐P. , Reinhardt K.
Published: December 2003

The partition equilibria of zirconium and hafnium thiocyanates between water and methyl isobutyl ketone have been studied under various conditions. Since the system shows extremely marked deviations from Nernst's distribution law, the two elements cannot be prepared in a very pure state by a simple multi‐stage partition. By the use of suitable additives and a new scheme of material flow, however, a continuous process using 23 mixer settlers has been developed, by means of which ZrO2 containing less than 10 p.p.m. of HfO2 and HfO2 containing only 0.3% of ZrO2 can be obtained from a zirconium‐hafnium mixture (hafnium content: 1 to 2%).
The Chemistry of Protactinium
Authors: Keller C.
Published: December 2003

Protactinium exhibits an ambivalent chemical behavior. In non‐aqueous solutions and in the solid state, both quadrivalent and quinquevalent protactinium has properties which characterize it as a typical actinide element. On the other hand, investigations in aqueous solution show quinquevalent protactinium to be a homologue of niobium and tantalum. It exhibits – except in hydrofluoric acid solutions – a marked tendency to undergo irreversible hydrolysis and condensation reactions, which leads to the situation that tracer amounts (ca. 10−12mole/l) and macroscopic amounts (10−3–10−6mole/l) of protactinium often behave differently. Reduction with strong reducing agents gives aqueous solutions of Pa(IV), the properties of which again correspond in general to those of Th(IV) and show no relation to Nb(IV). Our knowledge of the chemical behavior of this rare radioelement has been advanced, in particular, by the production in 1958–1960 of 100 g of pure protactinium – the largest amount so far – from residues of the British production of uranium.
The Kinetics of Crystal Growth
Authors: Heyer H.
Published: December 2003

The fundamentals of the theory of crystal growth comprise the two concepts of growth via two‐dimensional nuclei and growth with the aid of dislocations. Measurements of the relationship between rate of growth and supersaturation are particularly suitable for testing theoretical predictions. Experimental results are compared with predictions for crystal growth from the vapor phase, from solution, and from the melt. Depending on the experimental conditions, examples of both types of growth are met irrespective of the nature of the mother phase.
Kinetic Relationships between Reactions in the Gas Phase and in Solution
Authors: Martin H.
Published: December 2003

Some recent examples of reactions proceeding both in the gas phase and in solution have been investigated to determine their kinetics and mechanisms. The ratio of the corresponding rate constants, kG and kL, of the elementary processes studied has been found to be about unity for unimolecular reactions and between 1 and 10 for bimolecular reactions. The mechanisms, overall rates, rate constants, and activation energies have been determined for the homogeneous gas reaction NOCl + Cl2O = NO2Cl + Cl2 and the reaction NOCl + N2O5 = NO2Cl + 2 NO2, carried out in C2F3Cl3.
The Synthesis of Oligo‐ and Polynucleotides
Authors: Cramer F.
Published: December 2003

Problems and results of the synthesis of oligonucleotides are reviewed. The central role of the nucleic acids in biochemistry is a challenge to synthesize nucleic acids of known base sequence and chain length. Oligomers with various sequences of up to 12 members and homo‐oligomers with a maximum chain length of 30 nucleotides can be obtained by chemical synthesis. The enzymatic synthesis of ribonucleic acids can be directed in such a way that polynucleotides with definite sequences are produced.
Advances in Molecular Diamagnetism
Authors: Haberditzl W.
Published: December 2003

At the present state of instrumentation and quantum‐mechanical approximations, diamagnetic measurements can supply information on chemical structure which complements the result of other approaches, such as infrared and NMR spectroscopy. General applicability and relatively low cost of equipment are among the advantages of this technique. There is growing interest in the relation to chemical shifts in NMR spectra and in the possibility offered by this technique for testing quantum‐chemical approximations.
Structures and Reactions of Organic ate‐Complexes
Authors: Tochtermann W.
Published: December 2003

Some years ago, Wittig

G. Wittig, Angew.Chem.70, 65 (1958).

pointed out that ate‐complexes are characterized by anionic activation of the substituents attached to the central atom. The behavior of these compounds thus contrasts with that of the onium‐complexes

Cf.E. Müller: Neuere Anschauungen der organischen Chemie. Springer, Berlin 1957, p. 132–142

studied by Meerwein, which are characterized by cationic activation of the ligands. These two types of complexes form together two complementary aspects of organic coordination chemistry

Metal‐carbon π‐complexes are excluded from the following discussion.

.
The Chemistry of α‐Carbonyl Azo Compounds
Authors: Fahr E. , Lind H.
Published: December 2003

α‐Carbonyl azo compounds such as diesters of azodicarboxylic acids, diacylazo compounds, and esters of arylazocarboxylic acids are highly reactive. They add e.g. to amines, aromatic compounds, olefins, CH acids, Grignard and diazo compounds, aldehydes, ketones, and ketenes. These reactions can be used for the preparation of triazanes, hydrazones, oxa‐diazoline, azomethinimine, and diazetidine derivatives, etc. α,α′‐Dicarbonyl azo compounds are among the strongest dienophiles known.
Syntheses of Thiocarboxamides
Authors: Walter W. , Bode K.‐D.
Published: December 2003

Methods for the preparation of thiocarboxamides are described with special reference to progress achieved in the last few years. The discussion is arranged according to the eight most important reaction types.
Reactions of Elementary Silicon
Authors: Bonitz E.
Published: December 2003

Elementary silicon is normally treated “dry” with gaseous reactants in a fluidized bed. The apparent inertness of ordinary silicon is due to surface passivation. Non‐passivated silicon reacts as a strongly electropositive element. Finely divided silicon is pyrophoric and forms surface compounds with many substances (e.g. alcohol, water, and metal or organic halides) even at room temperature. An alternative to the “dry” process is a new suspension process, in which finely divided activated silicon, preferably suspended in its liquid reaction products (possibly in the presence of the soluble catalysts) reacts at elevated pressures, generally with liquids. The reactions in suspension can be easily controlled, and al the silicon is consumed. Polysilanes often are the only initial products, and these react further in the homogeneous liquid phase to give monosilanes. For example, dissolution of ordinary silicon in methanol leads smoothly to methoxysilanes, which can add to unsaturated hydrocarbons.
Snytheses and Reactions of O,N,N′‐Trisubstituted Isoureas
Authors: Däbritz E.
Published: December 2003

The CuCl2‐catalysed addition of alcohols to aliphatic caribodiimides (particularly diisopropylcarbodiimide) to form O,N,N′‐trialkylisoureas may, in the case of bifunctional hydroxy compounds (esters of α‐hydroxycarboxylic acids, diols, halogeno alcohols, amino alcohols, and cyclic hydroxy ethers), continue to give 5‐, 6‐, and 7‐membered 1,3‐O,N or 1,3‐N,N heterocycles. O,N,N′‐Trialkylisoureas are selective alkylating agents. Thus alcohols with allyl structures can be etherified with diisopropylcarbodiimide; a new method of esterification via O,N,N′‐trialkylisoureas has been applied to mesitylenecarboxylic acid.
Carbohydrates Containing Nitrogen or Sulfur in the “Hemiacetal” Ring
Authors: Paulsen H.
Published: December 2003

In 5‐amino‐5‐deoxy‐and 5‐thioaldoses, a 6‐membered hemiacetal ring can be formed by incorporation of a nitrogen or sulfur atom into the ring instead of the oxygen present in pyranoses. In the case of 5‐(N‐acylamido) ‐5‐ deoxyaldoses, the nucleophilic strength of the amide grouping is lowered, with the result that ring closure occurs only when sterically favored, or when a side reaction with formation of furanose is not possible. On the other hand, 5‐amino‐5‐deoxyaldoses containing a free amino group readily from 6‐membered “hemiacetal” rings. The resulting piperidinoses possess properties that are unusual in sugars, since they contain the 2‐hydroxypiperidine ring system. Piperidinoses are stable to alkalis and labile to acids; they rearrange in the presence of acids to give Amadori compounds, or lose three molecules of water to give derivatives of β‐hydroxypyridines. Owing to the high reactivity of the mercapto group, 5‐thioaldoses from only sugars with rings containing sulfur, the behavior of which resembles that of the oxygen analogues. 4‐Amino‐4‐deoxy‐ and 4‐thioaldoses can form 5‐membered rings containing nitrogen and sulfur.
An Apparatus for Titrations in Liquid Ammonia
Authors: Schenk P. W.
Published: December 2003

An apparatus for titrations in liquid ammonia is described. The titrations can be carried out in the absence of air, and the utility of the apparatus is demonstrated for a number of conductometric and potentiometric titrations.
Progress in the Chemistry of Casein
Authors: Jollès P.
Published: December 2003

Casein from cow's milk is not a single substance, but can be resolved into numerous components. These include x‐casein, which is the only fraction that contains appreciable quantities of sugars. This component plays a very important role in the clotting of milk by rennin, when it is split into an almost sugar‐free fraction, para‐x‐casein, and a fraction containing sugars, x‐caseinoglycopeptide. Caseinoglycopeptides have been isolated not only from the casein of cow's milk, but also from the caseins of sheep. Goat, and human milk. The second part of the paper deals with the clotting of milk by rennin and the amino acid sequence in caseinoglycopeptides.