Morita Endomorphism Algebras of Generators

We provide a characterization for the endomorphism algebra of a generator to be a Morita algebra. As an application, n-Auslander algebras which are Morita algebras simultaneously are characterized.     

Head-to-Head Polymers. XXVIII. Attempted Syntheses of Linear Head-to-Head Polyisobutylene

2,2,3,3-Tetramethyl-1,4-dibromobutane, when used as monomer for polymerization by Wurtz-type polycondensation, gave head-to-head polyisobutylene which is branched. Under similar conditions, 2, 5-dimethyl-2, 5-dibromohexane gave no polymer. Copolymerization of ethylene with tetramethylethylene under various conditions gave polyethylene of modest molecular weight with about 5% tetramethylene units in the polymer. 1,1,4, 4-Tetramethyl-1,3-butadiene (2,5-dimethylhexadiene-2,4) polymerized with BF₃ initiator to high molecular weight trans- 1,4-poly-(1,1,4,4-tetrarnethylbutadiene-1,3). The polymer could not be hydrogenated with soluble hydrogenation catalysts and only partially by chemical reduction with diimide. Under forcing conditions, incorporation of portions of the decomposition products of the precursor of the diimide was observed.     

Aldehyde Polymerization,Helical Polymers,Macromolecular Asymmetry,and Oligomers

Abstract

A historical development of the polymerization of higher aldehydes is presented. It shows the development of the polymerization of the simplest example, formaldehyde, the very ancient and to some extent incorrect history of other aldehyde polymerizations, and actually starts with the full understanding of this field as of the early 1950s. Much of the early work is incoherent and inconsistent, not surprisingly because of the limited knowledge of polymer chemistry that was available at that time. This contribution tries to correlate the polymerization of formaldehyde, the higher aliphatic aldehydes, and the trihaloacetaldehydes within the framework of a comprehensive understanding of the field of polymer science. The extensive progress in the field of trihaloacetaldehyde polymerization has led to the development of cryotachensic polymerization, the concept of optical activity based on macromolecular asymmetry, ultimately the recognition of the importance of the study of oligomers of stereoregular polymers, and the very essence of the embryonic state of addition polymerization.     

Head-to-Head Polymers. XXII. Toward the Synthesis of Pure Head-to-Head Poly(methyl Methacrylate): Copolymerization of 2,3-Dimethylmaleic Anhydride and Ethylene

Copolymerization of 2,3-dimethylmaleic anhydride and ethylene has been accomplished under ethylene pressure (up to 1000 psi) with AIBN as the initiator. The copolymers were obtained at relatively low yield and only of moderate molecular weight. The incorporation of 2,3-dimethylmaleic anhydride units into the copolymer is about 20 mol% at 1000 psi and is 33 mol% at 500 psi of ethylene pressure. Unlike maleic anhydride-ethylene copolymers, alternating 2,3-dimethylmaleic qnhydride-ethylene copolymers of reasonable molecular weight have not yet been prepared. 2,3-Dimethylmaleic anhydride-ethylene copolymers could be hydrolyzed to the polymeric acids and quantitatively esterified to the polymeric methyl esters. Both anhydride and ester copolymers have been characterized spectroscopically and by their thermal behavior.     

trans‐Chloro­(methyl)­bis­(tri­cyclo­hexyl­phosphine)­platinum(II)

The crystal structure of the title compound, [PtCl(CH₃)(C₁₈H₃₃P)₂], is isostructural with various platinum(II) and palladium(II) complexes containing two bulky tri­cyclo­hexyl­phosphine ligands in a trans orientation. The Pt atom resides on an inversion centre, resulting in a 50% statistical disorder in the chloro and methyl positions. The most significant geometrical parameters are Pt—P 2.3431 (8), Pt—­Cl 2.440 (4) and Pt—C1 2.179 (13) Å, and P—Pt—P 180, P—Pt—Cl 89.15 (12) and 90.85 (12), and C—Pt—Cl 172.7 (5)°. The effective and Tolman cone angles for the tricyclohexylphosphine ligands were calculated as 160 and 162°, respectively.     

Comparison of depth profiles in SIMS by a fuzzy method

Automated quantitative comparison of depth-profiles recorded by SIMS based on a fuzzy difference measure has been used to characterize Sb and B implantation profiles in a marker experiment to study the diffusion of As in silicon. The variations of the concentration (intensity) measurements are described by a fuzzy set that is specified by smoothing the data with a polynomial digital filter. For each depth an individual spread as the size of variation is defined. Applications of the method enabled the influence of As-concentration and of annealing conditions on the implantation profiles of Sb and B to be quantified.     

Mechanistic studies for modelling the metal ioncatalyzed tiron-hydrogen peroxide indicator reaction

Model building of kinetic-catalytic methods of determination is attempted for the tironhydrogen peroxide indicator reaction catalyzed by cobalt(II) and manganese(II) in alkaline medium. As a first approximation, rate equations for the metal ion-catalyzed reactions are derived from kinetic dependences on reagent concentrations and pH. More general models are obtained by considering the metal ion equilibria in the reaction mixture. For Co(II), a ternary tironhydrogen peroxideCo(II) complex was found to be responsible for the catalytic activity. As stability constants of peroxo (Co(II) complexes are unknown, only a qualitative approach can be given. Manganese catalyzes the indicator reaction in the presence of 1,10-phenanthroline or 2,2′-bipyridine. The initial rates under pseudo zero-order conditions in hydrogen peroxide and tiron correlate directly with the fraction of ternary activatortironMn(II) complex present. For bipyridine as activator, the rate constant is 1.31 × 10⁶ M^?1 min^?1 with respect to the ternary complex.     

Continuous‐Flow Synthesis of CdSe Quantum Dots: A Size‐Tunable and Scalable Approach

In recent years, continuous‐flow/microreactor processing for the preparation of colloidal nanocrystals has received considerable attention. The intrinsic advantages of microfluidic reactors have opened new opportunities for the size‐controlled synthesis of nanocrystals either in the laboratory or on a large scale. Herein, an experimentally simple protocol for the size‐tunable continuous‐flow synthesis of rather monodisperse CdSe quantum dots (QDs) is presented. CdSe QDs are manufactured by using cadmium oleate as cadmium source, selenium dioxide as selenium precursor, and 1‐octadecene as solvent. Exploiting selenium dioxide as selenium source and 1‐octadecene as solvent allows execution of the complete process in open air without any requirement for air‐free manipulations using a glove box or Schlenk line. Continuous‐flow processing is performed with a stainless steel coil of 1.0 mm inner diameter pumping the combined precursor solution through the reactor by applying a standard HPLC pump. The effect of different reaction parameters, such as temperature, residence time, and flow rate, on the properties of the resulting CdSe QDs was investigated. A temperature increase from 240 to 260 °C or an extension of the residence time from 2 to 20 min affords larger nanocrystals (range 3–6 nm) whereas the size distribution does not change significantly. Longer reaction times and higher temperatures result in QDs with lower quantum yields (range 11–28 %). The quality of the synthesized CdSe QDs was confirmed by UV/Vis and photoluminescence spectroscopy, small‐angle X‐ray scattering, and high‐resolution transmission electron microscopy. Finally, the potential of this protocol for large‐scale manufacturing was evaluated and by operating the continuous‐flow process for 87 min it was possible to produce 167 mg of CdSe QDs (with a mean diameter of 4 nm) with a quantum yield of 28 %.     

A specific micromethod for the determination of phytic acid in biological material

A method for the quantitative determination of phytic acid in biological material is described. The method permits a determination of phytic acid in quantities below 0.1 mg even if the material contains closely related compounds includingmyo-inositol pentakisphosphate.

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Eine spezifische Mikromethode für die Bestimmung von Phytinsäure in biologischem Material

Zusammenfassung Es wird eine Methode zur quantitativen Bestimmung von Phytinsäure in biologischem Material beschrieben. Die Methode erlaubt die Bestimmung von Phytinsäure in Mengen von weniger als 0.1 mg, selbst wenn das Untersuchungsmaterial nahe verwandte Substanzen wie z. B.myo-Inositpentakisphosphat enthält.