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  • 1
    Electronic Resource
    Electronic Resource
    Diffusional boundary spreading in the ultracentrifuge (1970)
    New York : Wiley-Blackwell
    Biopolymers 9 (1970), S. 865-874 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A common approximation for deriving solutions to the Lamm equation is to neglect diffusion. This paper presents a singular perturbation technique that allows one to estimate the band spreading due to nonzero diffusion coefficient. We illustrate the general mathematical technique by its application to sedimentation when pressure effects are important. Comparison of the approximate solution with accurate numerical solutions shows that the relative errors are of the order of 1% both for concentration and concentration gradient for parameters of chemical interest.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1970.360090710
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  • 2
    Electronic Resource
    Electronic Resource
    Magnitude of a finite equilibration effect in analytical gel chromatography (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 2125-2130 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous analyses of solute behavior in analytical gel chromatography1,2 have allowed for a finite equilibration time between stationary and mobile phases in estimating the magnitude of axial dispersion coefficients, but have ignored these effects in formulating the continuity equations for solute transport. We develop a more accurate theory including the equilibration effect, and show experimentally that it can be disregarded after approximately two minutes from the start of a small-zone experiment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360111012
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  • 3
    Electronic Resource
    Electronic Resource
    Instability in pressure-dependent sedimentation of monomer - polymer systems (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 2477-2490 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possibility of convection in velocity sedimentation studies on pressure dependent associating systems is known both experimentally and theoretically. We present accurate numerical solutions to the Lamm equation to illustrate this phenomenon for monomer-polymer systems. An approximate theory based on the absence of diffusion is then developed to predict the onset of convection. Comparison of the theory with the numerical solutions shows it to be quite accurate.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360121104
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  • 4
    Electronic Resource
    Electronic Resource
    Kristallstrukturen und kernmagnetische Breitlinienresonanz der Alkalisilyle SiH3M (M = K, Rb, Cs) (1970)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 2868-2872 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Structures and Nuclear Magnetic Wide-Line Resonance of Alkali Silyl Compounds SiH3M (M = K, Rb, Cs)The crystal structure of SiH3K, SiH3Rb and SiH3Cs is of the NaCl-type at room temperature (lattice constants a = 7.23, 7.52 and 7.86 Å, resp.). For the silyl anion, SiH3--, an effective ionic radius of 2.26 Å can be derived. The different structure in comparison with CH3K (NiAs-type) is explained by the more spheric shape of the SiH3--ions. A n. m. r. wide-line investigation of SiH3K shows rotation of the SiH3-groups at their sites at room temperature. Below -100° the SiH3-groups are fixed. Their H-H-distances are 2.17 Å. Assuming normal Si-H-distances a H-Si-H-bond angle of 94±4° can be derived for the silyl anion.
    Notes: SiH3K, SiH3Rb und SiH3Cs haben bei Raumtemperatur Kristallstrukturen vom NaCl-Typ (Gitterkonstanten a = 7.23, 7.52 bzw. 7.86 Å). Hieraus resultiert für das Silyl-Anion, SiH3-, ein effektiver Ionenradius von 2.26 Å. Die gegenüber CH3K (NiAs-Typ) abweichenden Kristallstrukturen werden auf die mehr kugelförmige Gestalt der SiH3--Ionen zurückgeführt. Aus einer kernmagnetischen Breitlinienresonanzuntersuchung von SiH3K ergibt sich bei Raumtemperatur eine Rotation der SiH3-Gruppen auf ihren Gitterplätzen. Unterhalb-100° sind dagegen die Silylgruppen fixiert mit zu 2.17 Å gemessenen H-H-Abständen. Unter Zugrundelegung des normalen Si-H-Abstands folgt hieraus ein H-Si-H-Valenzwinkel des Silyl-Anions von 94±4°.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19701030924
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  • 5
    Electronic Resource
    Electronic Resource
    Übergangsmetall-Carben-Komplexe, LIV. Der Pentacarbonyl(phenylcarben)chrom(0)-Rest als Amino-Schutzgruppe für Peptid-Synthesen (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 1277-1284 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal Carbene Complexes, LV. Pentacarbonyl(phenylcarbene)chromium(0) as an Amino-Protecting Group in Peptide SynthesesAminolysis of pentacarbonyl[methoxy(phenyl)carbene]chromium(0) with aminoacid esters L-Phe-OMe, L-Pro-OMe, and L-Ala-OMe yields the corresponding N-carbene complexes 1-3 from pentacarbonyl(phenylcarbene)chromium(0) and the aminoacid esters. In the case of the L-Ala-OMe derivative the use of pentacarbonyl(phenylcarbene)chromium(0) as aminoprotecting group in peptide synthesis is studied. After alkaline hydrolysis of the methyl ester, reaction with L-Ala-OMe using the NHS/DCCD method gives the dipeptide derivative pentacarbonyl(phenylcarbene-L-Ala-L-Ala-OMe)chromium(0) (5), which yields analogously the tripeptide derivative pentacarbonyl(phenylcarbene-L-Ala-L-Ala-L-Ala-OMe)chromium(0) (6). 1H n.m.r., i.r. and mass spectra of the new compounds are discussed. The protecting group is cleaved off with trifluoroacetic acid at 20°C.
    Notes: Die Aminolyse von Pentacarbonyl[methoxy(phenyl)carben]chrom(0) mit den Aminosäureestern L-Phe-OMe, L-Pro-OMe und L-Ala-oMe liefert die entsprechenden N-Carbenkomplexe 1-3 aus Pentacarbonyl(phenylcarben)chrom(0) und den L-Aminosäure-methylestern. Am Beispiel des L-Ala-OMe-Derivates wird die Verwendung des Pentacarbonyl(phenylcarben)chrom(0)-Restes als Amino-Schutzgruppe für Peptidsynthesen untersucht. Nach der alkalischen Verseifung des Methylesters führt die Umsetzung mit L-Ala-OMe nach der NHS/DCCD-Methode zum Dipeptid-Derivat Pentacarbonyl(phenylcarben-L-Ala-L-Ala-OMe)chrom(0) (5), das in analoger Reaktion Zum Tripeptid-Derivat Pentacarbonyl(phenylcarben-L-Ala-L-Ala-L-Ala-OMe)chrom(0) (6) umgesetzt wird. 1H-NMR-, IR- und Massenspektren der neuen Verbindungen werden diskutiert. Die Abspaltung der Schutzgruppe erfolgt durch Trifluoressigsäure bei 20°C.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060424
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  • 6
    Electronic Resource
    Electronic Resource
    Umsetzungen von O-, N- und S-Carbenpentacarbonylchrom(0)-Komplexen mit N-Acyliminen des Hexafluoracetons zu Oxazolin-Derivaten und Thioäthern (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 1581-1588 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal Carbene Complexes, LVI. Reactions of O-, N- and S-Carbenepentacarbonylchromium(0) Complexes with N-Acylimines of Hexafluoroacetone to Oxazoline Derivatives and ThioethersReactions of [alkoxy(aryl)carbene]-, [alkoxy(alkyl)carbene]- and [dimethylamino(phenyl)-carbene]pentacarbonylchromium(0) complexes with N-acylimines of hexafluoroacetone yield by ring-formation at elevated temperatures oxazoline derivatives, whereas reaction of [methyl(methylthio)carbene]pentacarbonylchromium(0) gives thioether derivatives with cleavage of the carbene ligand. 1H-n.m.r., i.r. and mass spectra of the new compounds are discussed.
    Notes: Umsetzungen von [Alkoxy(aryl)carben]-, [Alkoxy(alkyl)carben]- und [Dimethylamino(phenyl)carben]-pentacarbonylchrom(0)-Komplexen mit N-Acyliminen des Hexafluoracetons führen bei erhöhten Temperaturen unter Ringschluß zu Oxazolin-Derivaten, während die Umsetzung von [Methyl(methylthio)carben]pentacarbonylchrom(0) unter Spaltung des Carbenliganden Thioäther-Derivate ergibt. 1H-NMR-, IR- und Massenspektren der neuen Verbindungen werden diskutiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060523
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  • 7
    Electronic Resource
    Electronic Resource
    Die Kristallstrukturen der Alkalimethylmercaptide CH3SM (M = Li, Na, K) (1972)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 481-486 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Crystal Structures of Alkali Methane Thiolates CH3SM (M = Li, Na, K)The crystal structures of the alkali methane thiolates CH3SM (M = Li, Na, K) have been determined from X-ray powder data. All compounds have tetragonal lattices (space group P 4/nmm). CH3SLi and CH3SNa are of the same type as CH3OLi and CH3ONa, whereas CH3SK is of the CH3OK-type. Both types represent layer structures with CH3S groups having an antiparallel arrangement to each other along the c axis. In this way each layer is covered by methyl groups on both sides. The alkali ions are located in the central part of the layer, being co-ordinated by four (M =Li, Na) or five (M = K) sulfur ions.
    Notes: Die Kristallstrukturen der Alkalimethylmercaptide CH3SM (M = Li, Na, K) wurden aus Pulverdaten ermittelt. Alle Verbindungen kristallisieren tetragonal (Raumgruppe P 4/nmm); dabei sind CH3SLi und CH3SNa isotyp mit CH3OLi, während CH3SK vom CH3OK-Typ ist. In beiden Typen liegen Schichtstrukturen vor. Die CH3S-Gruppen sind antiparallel zueinander in Richtung der c-Achse angeordnet. Jede Schicht ist damit außen von Methylgruppen bedeckt, während die Alkali-Ionen im Schichtinneren von vier (M = Li, Na) bzw. fünf (M = K) Schwefel-Ionen koordiniert sind.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19721050214
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  • 8
    Electronic Resource
    Electronic Resource
    Darstellung und Kristallstruktur des Tetrakis(π-cyclopentadienyl)-di-μ-silyleno-dititans [(C5H5)2TiSiH2]2 (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 1747-1751 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Crystal Structure of Tetrakis(π-cyclopentadienyl)-di-μ-silyleno-dititanium [(C5H5)2TiSiH2]2The silylation of (C5H5)2TiCl2 with SiH3K yields olive-green [(C5H5)2TiSiH2]2 (1), soluble in benzene. The compound crystallizes in the tetragonal space group P42/mnm (a = 8.018 Å, c = 16.113 Å; Z = 2). The molecule consists of two (C5H5)2Ti units linked by two SiH2 bridges. The bond angle Ti—Si—Ti is 102.8° and thus differs little from the tetrahedral angle.
    Notes: Die Silylierung von (C5H5)2TiCl2 mit SiH3K ergab in Benzol lösliches olivgrünes [(C5H5)2TiSiH2]2 (1), das in der tetragonalen Raumgruppe P42/mnm (a = 8.018 Å, c = 16.113 Å; Z = 2) kristallisiert. Im Molekül liegen zwei (C5H5)2Ti-Einheiten vor, die über zwei SiH2-Brücken verknüpft sind. Der Valenzwinkel Ti—Si—Ti beträgt 102.8°d und liegt damit nur wenig unter dem Tetraederwinkel.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060608
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  • 9
    Electronic Resource
    Electronic Resource
    Übergangsmetall-Carben-Komplexe, LXXVIII. Reaktion von Pentacarbonyl(hydroxymethylcarben)chrom(0) mit Dicyclohexylcarbodiimid (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 3548-3553 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal Carbene Complexes, LXXVIII. Reaction of Pentacarbonyl(hydroxymethylcarbene)chromium(0) with DicyclohexylcarbodiimidePentacarbonyl(hydroxymethylcarbene)chromium(0) reacts with dicyclohexylcarbodiimide (DCCD) by intramolecular elimination of water and subsequent cycloaddition of DCCD to give pentacarbonyl(1-cyclohexyl-4-cyclohexylimino-2-carbena-azetidine)chromium(0)(1). As by-product the ureidocarbene complex pentacarbonyl[N,N′-dicyclohexylureido(methyl)carbene]-chromium(0) (2) is formed via O,N-carbenyl rearrangement.
    Notes: Die Umsetzung von Pentacarbonyl(hydroxymethylcarben)chrom(0) mit Dicyclohexylcarbodiimid (DCCD) führt über intramolekular Wasserabspaltung und anschließende Cycloaddition von DCCD zu Pentacarbonyl(1-cyclohexyl-4-cyclohexylimino-2-carbena-azetidin)chrom(0) (1). Als Nebenprodukt entsteht durch O,N-Carbenylumlagerung der Ureidocarben-Komplex Pentacarbonyl[N,N′-dicyclohexylureido(methyl)carben]chrom(0)(2).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741071109
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  • 10
    Electronic Resource
    Electronic Resource
    Aminyloxide, XIV. Der Einfluß von Heterosubstituenten am Kohlenstoffatom von Azomethin-aminyloxiden auf Spindichteverteilung und Molekülgeometrie (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 2845-2853 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aminyl Oxides, XIV. The Effect of Hetero Substituents at the Carbon Atom of Azomethine Aminyl Oxides on the Spin Distribution and the Geometry of the MoleculeAzomethine aminyl oxides substituted at the carbon atom of the azomethine group by hetero substituents X (5, 8) (type B) and radicals bridged by hetero substituents (4) (type A) were prepared. E.s.r. studies with A and B showed that the spin density is increased at the aminyl oxide nitrogen and decreased at the azomethine nitrogen by electron donating substituents. On the other hand electron accepting substituents favour delocalisation into the azomethine group. For radicals B additional steric effects become pronounced with increasing bulkiness of the group R1R2N.
    Notes: Azomethin-aminyloxide mit Heterosubstituenten X am C-Atom der Azomethingruppe (5, 8) (Typ B) und durch Heterosubstituenten verbrückte Radikale (4) (Typ A) wurden synthetisiert. Wie die ESR-spektroskopische Untersuchung ergab, verursachen Elektronendonator-Substituenten X in A und B eine Spindichteerhöhung am Aminyloxidstickstoff und eine Spindichteerniedrigung am Azomethinstickstoff. Durch Elektronenacceptor-Substituenten wird dagegen die Delokalisierung in die Azomethingruppe erhöht. In den Radikalen B werden mit wachsender Größe des Rests R1R2N zusätzlich sterische Effekte wirksam.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060912
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