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  • Chemistry  (32)
  • 2020-2022  (1)
  • 1985-1989  (26)
  • 1970-1974  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Cycloadditionsreaktionen von Heterocumulenen, XXIX. Reaktion von Thioketenen mit Isocyanaten (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 689-699 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloaddition Reactions of Heterocumulenes, XXIX.  -  Reactions of Thioketenes with IsocyanatesThe [2 + 2] cycloaddition of thioketenes 1a-f to isocyanates 2a-f yields 4-thioxo-2-azetidinones 3 as main products, which may isomerize to 4-imino-2-thietanones 5. In competing reactions, 2,4-azetidinediones 8, N-sulfonylamides 9, and 3H-1,2,4-dithiazoles 15 are formed. Thioketenes 1 react with chlorosulfonyl isocyanate (20b) to give N-unsubstituted 4-thioxo-2-azetidinones 22. Depending on the thioketene 1 and the reaction conditions, compounds 23-26 also result. The constitutions of 15b and 23a were determined by X-ray structural analyses.
    Notes: Die [2 + 2]-Cycloaddition der Thioketene 1a-f an die Isocyanate 2a-f liefert als Hauptprodukt 4-Thioxo-azetidinone 3, die sich zu 4-Imino-2-thietanonen 5 isomerisieren können. In Konkurrenzreaktionen werden 2,4-Azetidindione 8, N-Sulfonylamide 9 und 3H-1,2,4-Dithiazole 15 gebildet. Mit Chlorsulfonylisocyanat (20b) reagieren die Thioketene 1 zu N-unsubstituierten 4-Thioxo-2-azetidinonen 22. Je nach Thioketen 1 und Reaktionsführung resultieren auch die Verbindungen 23-26. Die Konstitution von 15b und 23a wurde durch Röntgenstrukturanalyse bestimmt.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210416
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  • 2
    Electronic Resource
    Electronic Resource
    1,3-Diazabutadiene: Kristallstruktur, quantenmechanische Berechnungen und spektroskopische Untersuchung (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1705-1710 
    Details
    ISSN: 0009-2940
    Keywords: 1,3-Diazabutadienes ; ab initio calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Diazabutadienes: Crystal-Structure Analysis, Quantum-Mechanical Calculations, and Spectroscopic InvestigationThe X-ray analysis of derivative 3a (available from the corresponding amidine and aldehyde by titanium tetrachloride assisted condensation) shows, that the substituent at the nitrogen atom N1 prefers the (Z)position. The heterobutadiene chain is strongly twisted [Θ(N2—C7—N1—C8) = 109.7°], indicating only weak conjugative interactions between the two C=N units. The dynamic properties of 1,3-diazabutadiene (4) (N-methyleneformamidine) were simulated by ab initio calculations (3-21G, MP2/6-31G*). The global minimum corresponds to the s-trans isomer 4a with (Z) configuration at N1 = C2; a gauche form (local minimum) 4c is slightly higher in energy. For the (E)-N1=C2 isomers, gauche structure 4d is lowest in energy, the s-trans form 4b is less favourable by 2-3 kcal/mol. The calculated rotational barriers (2-7 kcal/mol) are similar to those of butadiene. Inversion processes also have low barriers: Transition structures with linear, sphybridized nitrogen atoms N3 and orthogonal positions of the N3=C4 unit were found (Erel ≍ 20 kcal/mol). IR1H-, 13C-NMR, and UV data are given and compared with the results of the structural investigations.
    Notes: Die Kristallstrukturbestimmung des durch Kondensation des entsprechenden Amidins unter Aldehyds Titantetrachlorid-Zusatz erhältlichen Derivates 3a zeigt, daß sich der Substituent am Stickstoff-Atom N1 in der (Z)-Position befindet. Das Heterobutadien-Gerüst fällt durch seinen großen Torsionswinkel [Θ(N2—C7—N1—C8) = 109.7°] auf und läßt auf nur schwache konjugative Wechselwirkungen zwischen den beiden C=N-Einheiten schließen. Die dynamischen Eigenschaften von 1,3-Diazabutadien (4) (N-Methylenformamidin) wurden durch ab-initio-Berechnungen (3-21 G, MP2/6-31G*) simuliert. Demnach ist die günstigste Struktur die s-trans-Form 4a mit (Z)-Konfiguration an N1 = C2; daneben existiert ein gauche-Minimum 4c mit geringfügig höherer Energie. Für die (E)-N1=C2-Konfiguration ist die gauche-Form 4d am energieärmsten, die s-trans-Struktur 4b entspricht einem lokalen Minimum (Erel ≍ 2-3 kcal/mol). Die berechneten Rotationsbarrieren (2-7 kcal/mol) sind denen von Butadien vergleichbar. Auch Inversionsprozesse an N3 haben niedrige Barrieren: Es konnten Übergangszustände mit linearem, sphybridisiertem Stickstoff-Atom N3 und orthogonaler Stellung der N3=C4-Einheiten ermittelt werden (Erel ≍ 20 kcal/mol). IR1H-, 13C-NMR- und UV-Daten werden zugeordnet und mit den Strukturergebnissen verglichen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220917
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  • 3
    Electronic Resource
    Electronic Resource
    Über das Reaktionsverhalten von 4-Thioxo-2-azetidinonen (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 701-707 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Reactivity of 4-Thioxo-2-azetidinonesBase-catalyzed alcoholysis of the N—S bond in N-sulfonylthioxoazetidinones 1 is a ready process; the resulting sulfonate then alkylates the liberated 2-. Alkylations of 2 under various conditions demonstrate that charge and thermodynamic control favor attack on nitrogen to give 5 rather than reaction on sulfur to give 4. Besides simple alkyl residues (4a-c, 5a-c) also functionalized alkyl (4d, e, g, m, n, o, 5d, e, g, i, m-o), aryl (5p), and acyl groups (5q) can be introduced and addition reactions (5r, s) achieved. Complex hydrides reduce the carbonyl group in 1,5 to yield 8-10, but the C=N+ unit in the salt 6a to furnish β-lactam 11. Annulation of a five-membered ring to give 12 is achieved by 1,3-dipolar cycloaddition of dimethyl fumarate to in-situ generated azomethine ylide 6d.
    Notes: Die basenkatalysierte Alkoholyse der N—S-Bindung in N-Sulfonyl-thioxoazetidinonen 1 tritt leicht ein; der entstehende Sulfonsäureester alkyliert dann das freigesetzte 2-. Unter verschiedenen Bedingungen durchgeführte Alkylierungsreaktionen an 2 zeigen, daß Ladungs- und thermodynamische Kontrolle den Angriff am Stickstoff zu 5 gegenüber der Reaktion am Schwefel zu 4 begünstigen. Neben einfachen Alkyl-Resten (4a-c, 5a-c) lassen sich auch funktionalisierte Alkyl-(4d, e, g, m, n, o, 5d, e, g, i, m-o), Aryl- (5p) und Acyl-Gruppen (5q) einführen sowie Additionsreaktionen (5r, s) erreichen. Komplexe Hydride reduzieren die Carbonyl-Gruppe in 1, 5 zu 8-10, aber den C=N+-Teil im Salz 6a zum β-Lactam 11. Die Anellierung eines Fünfrings zu 12 gelingt über die 1,3-dipolare Cycloaddition von Fumarsäure-dimethylester an das in situ freigesetzte Azomethin-Ylid 6d.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210417
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  • 4
    Electronic Resource
    Electronic Resource
    Notiz zum Problem des Substituentenaustausches bei der Grignard-Alkylierung von PhenylsilanenDie vorliegende Notiz ist als Diskussionsbeitrag zum Thema „Austauschreaktionen bei Organometallverbindungen“ gedacht. Das behandelte Problem wird von uns experimentell nicht weiter verfolgt. (1970)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 1302-1305 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19701030434
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  • 5
    Electronic Resource
    Electronic Resource
    Melting, crystallization, and solution behavior of chain molecules with hydrocarbon and fluorocarbon segments (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 911-925 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Melting, crystallization, and solution behavior of n-alkanes with fluorocarbon segments of twelve carbon atoms on one end, F(CF2)12(CH2)nH, or on both ends, F(CF2)12(CH2)n(CF2)12F were investigated by DSC, MAS 13C NMR, light scattering, and birefringence studies. Both triblock F(CF2)m(CH2)n(CF2)mF and diblock F(CF2)12(CH2)nH compounds with 4 ≦ n ≦ 14 melt by a two-step process. In the first step, the alkyl segment conformations gain nearly liquid like trans/ gauche ratios, while the perfluorinated segments remain ordered. “Gels” which incorporate the entire solvent are formed by crystallization from even dilute solutions of hydrocarbon and fluorocarbon solvents. The gels are built up of extremely long, interdigitated needles of the pure solute. Due to the bilayer structures and different degrees of ordering of the hydrocarbon and the fluorocarbon segments, the crystals grow preferentially in the direction parallel to the lamellar surface. Light scattering experiments in octane demonstrated the formation of micelle type associates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021890422
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  • 6
    Electronic Resource
    Electronic Resource
    Phase transitions and defect structure in the lamellar surface of polyethylene and n-alkane crystallites. Magic angle spinning 13C NMR studiesHerrn Professor Dr. R. Kosfeld zum 60. Geburtstag gewidmet (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1237-1252 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Variable temperature magic angle spinning 13C NMR experiments on linear alkanes and low molecular weight polyethylene allowed the observation of up to six carbon atoms at the chain ends near the surface of the lamellar crystallites. Conformational order-disorder and intermolecular packing effects are reflected by the spectra. The effects are discussed with regard to the peculiar phase behaviour of the n-alkanes and the fringed micella model for low molecular weight polyethylene. The solid-solid transitions of nonadecane and hexatriacontane appear to be correlated with the occurrence of specific non-liquid-like conformational disordering. Thus, conformational defects were observed for the “rotator phase” which depend on the chain length and which vary along the chain. Whilst the center part of the chain remains all-trans ordered, significant gauche defects were observed for the bonds at the chain ends. For a polydisperse low molecular weight linear polyethylene as well as for monodisperse octahexacontahectane reversible liquid-like conformational disordering of the terminal chain segments could be detected when the melting point was approached. Hence, in this case the NMR spectra indicate pre-melting of the lamella surface, while in case of the shorter n-alkanes the occurrence of end-gauche defects is correlated with solid-solid transitions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870520
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  • 7
    Electronic Resource
    Electronic Resource
    Poly(2-vinylpyridine) block copolymers. Phase separation and electric conductivity of iodine complexesDedicated to Prof. Dr. H.-J. Cantow on the occasion of his 65th birthday (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1153-1168 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of AB diblock copolymers of poly(2-vinylpyridine) (P-2VP) and either polybutadiene or polystyrene were prepared in a nonpolar solvent at low temperature. Well-defined polymers with narrow molecular weight distributions were obtained and electron micrographs showed that these block copolymers form a well-separated two-phase morphology. Percolation of P-2VP domains could be achieved for samples with 40 and with 60 mol-% of P-2VP blocks. These samples were modified by addition of various amounts of iodine in solution and in the melt. Electric conductivities of the doped composites were determined by the four-probe method. The conductivities of the two phase systems were, in general, lower than that of P-2VP doped with I2.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900521
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  • 8
    Electronic Resource
    Electronic Resource
    Einflüsse von Legierungselementen auf die Korrosion und Wasserstoffaufnahme von Eisen in Schwefelsäure - Teil II: Korrosion und DeckschichtbildungHerrn Professor Dr. rer. nat. Hans-Jürgen Engell zum 60. Geburtstag gewidmet (1985)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 36 (1985), S. 447-454 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Effects of Alloying Elements on Corrosion and Hydrogen Uptake of Iron in Sulfuric Acid Part II: Corrosion and Formation of Surface LayersThe effects of C, S, P, Mn, Si, Cr, Ni, Sn and Cu on the formation of surface layer and hydrogen uptake of iron during corrosion in 1 M H2SO4/N2 were investigated using AES, XPS, SEM and electrochemical permeation techniques.Cu, Sn, P and C are enriched on the surface of iron during corrosion in H2SO4. Cu is enriched in the metallic form. P forms a phosphate and phosphide containing surface layer. Ni is not enriched. Cr is preferentially dissolved. Cu, Sn and Ni inhibit the dissolution of iron and thus decrease the hydrogen activity. S, P and Mn (MnS) increase the corrosion and hydrogen activity. Cr forms traps in iron which increase the hydrogen uptake.
    Notes: Die Einflüsse von C, S, P, Mn, Si, Cr, Ni, Sn und Cu auf Deckschichtbildung und Wasserstoffaufnahme bei Korrosion von Eisen in 1 M H2SO4/N2 wurden mit AES, XPS, REM sowie der elektrochemischen Permeationsmethode untersucht.Cu, Sn, P und C reichern sich bei Korrosion von Eisen in H2SO4 an der Oberfläche an. Cu bleibt metallisch liegen. P bildet eine phosphat-und phosphidhaltige Deckschicht. Ni reichert sich nicht an. Cr geht bevorzugt in Lösung. Cu, Sn und Ni hemmen die Eisenauflösung und erniedrigen die Wasserstoffaktivität. S, P und Mn (MnS) erhöhen die Korrosionsgeschwindigkeit und die Wasserstoffaktivität. Cr bildet Wasserstoffallen in Eisen, die die Wasserstoffaufnahme erhöhen.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19850361004
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of phosphorus on the stability of the passive state of Fe and Fe-Ni base glasses (1988)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 39 (1988), S. 453-462 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Einfluß von Phosphor auf die Stabilität des passiven Zustands von metallischen Gläsern basierend auf Fe und Fe-NiFür metallische Gläser basierend auf Fe und Fe-Ni wurde der Einfluß einer Substitution von B durch P untersucht. Die elektrochemischen Messungen haben gezeigt, daß der Austausch von B gegen P die Bildung von Passivschichten begünstigt und deren passiven Bereich stabilisiert. Oberflächenanalytische Untersuchungen mittels AES ergaben, daß für die auf Fe-Ni basierenden Gläser die Hauptbestandteile der Passivschicht Eisenoxide, Phosphor-Sauerstoff Spezies (meistens Phosphate) und Boroxid waren, während Nickeloxid praktisch nicht auftrat. Bezüglich der Phosphorverbindungen in der Passivschicht auf dem metallischen Substrat konnte eine gewisse Ähnlichkeit festgestellt werden mit Phosphor, der auf einer (100) orientierten Fe Einkristalloberfläche durch Segregation bei erhöhter Probentemperatur angereichert und anschließend oxidiert worden war. Darüber hinaus lassen die Ergebnisse, in Übereinstimmung mit früheren Befunden für kristallines Fe, vermuten, daß Bestandteile des Elektrolyten in den Passivfilm auf dem glasartigen Substrat inkorporiert werden.
    Notes: The effects of substituting P for B in Fe base and Fe-Ni base glasses have been investigated. The electrochemical measurements have shown that a substitution of B by P increases the ability of the alloys to passivate and stability of their passive state. Surface analysis with AES revealed that for Fe-Ni base glasses the main constituents of the passive film were: iron oxides, phosphorus-oxygen species (mostly phosphates) and boron oxide whereas Ni oxides were depleted. There was a certain similarity between the Auger spectra for phosphorus in the passive film on the glassy substrate and for segregated, and subsequently oxidized, phosphorus on a (100) oriented Fe single crystal. The results suggest, moreover, in agreement with the previous findings for crystalline Fe that the electrolyte components are incorporated into the passivating film on glassy substrates.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19880391003
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  • 10
    Electronic Resource
    Electronic Resource
    Liquid chromatographic-mass spectrometric analysis of 2-nitrofluorene and its derivatives (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 13 (1986), S. 681-688 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid chromatography-mass spectrometry (LC-MS) with a nebuliser and a moving belt was used to characterise 2-nitrofluorene, its metabolites and related compounds. In total, 18 different compounds were analysed. The LC-MS interface did not affect the chromatographic performance achieved by high performance liquid chromatography (HPLC). The method allowed determination of the positions of the hydroxyl groups in different hydroxylated 2-acetylaminofluorene derivatives. The LC-MS procedure generated acceptable mass spectra with as small amounts of substance as 65 ng. The dose-response curves from the HPLC-detector and the ion-source in the LC-MS were parallel and linear.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200131208
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