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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Macromolecular conformation studies by variable temperature 13C and 29SI-NMR magic angle spinning (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 7 (1984), S. 63-85 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.020071984105
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  • 3
    Electronic Resource
    Electronic Resource
    Mesomorphic flexible chain polymers based on silicon (1994)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 796-804 
    Details
    ISSN: 1042-7147
    Keywords: Poly(dialkylsiloxane) ; Polysilane ; Polysilylene ; Columnar 2D-ordering ; Mesophases ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Poly(dialkylsiloxane)s and poly(dialkylsilane)s form a similar type of columnar mesophase. Although, the polysilanes are stiffer than polysiloxanes, both classes of polymers may be considered to be flexible due to the ability to form chain-folded crystals. Chain flexibility rather than the presence of chain stiffness determines whether the columnar mesophase is formed. A certain amphiphilic character does not appear to be required, as polysiloxanes with short side groups, e.g. polydiethylsiloxane display the same mesophase behaviour as polydialkylsilanes with long side chains and other nonpolar flexible chain molecules. The importance of the entropy gain upon conformational disordering is reflected in the increase in temperature stability with increasing alkyl side group length and the absence of mesophase behaviour in the case of the dimethyl substituted polymers
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1994.220051205
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  • 4
    Electronic Resource
    Electronic Resource
    Biogasgewinnung aus Reststoffen der Lebensmittel-Industrie (1992)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 64 (1992), S. 819-820 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330640975
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  • 5
    Electronic Resource
    Electronic Resource
    Nanofibrillar surface structures of gel-drawn UHMW-polyethylene tapes (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 492-497 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fibrillar structure of gel-drawn ultrahigh molecular weight polyethylene was studied by scanning force microscopy (SFM), transmission electron microscopy (TEM) and 2H-NMR. Periodically striped 20 - 50 nm wide nanofibrils were depicted at the surface of the ultradrawn tapes. A periodicity of about 25 nm was observed independently of the draw ratio in the range 10 ≤ λ ≤ 70. This is consistent with the long period derived from SAXS experiments. The stripes were more pronounced at low draw ratios and a short range interfibrillar correlation was detected in that case. Based on variations in the 2H-NMR relaxation times and segment orientation, it is concluded that structural defects are concentrated within small domains inside the crystallites and that the striped structure originates from defect layers within the fibrillar crystallites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471104
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  • 6
    Electronic Resource
    Electronic Resource
    Poly(di-n-pentylsilylene) copolymers containing diethyleneglycol-diethylether side chains (1997)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 48 (1997), S. 319-325 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(dipentylsilylene) copolymers containing 4,7,10-trioxadodecylmethylsilylene units as comonomer were synthesized via a Wurtz-type coupling reaction from the corresponding dichlorosilanes. The copolymers were characterized by GPC and NMR spectroscopy. Solvent- and temperature-dependent UV absorption was observed. The bulk polymers underwent broad endothermic transitions below room temperature, whose temperature and heat effect depended on the incorporation of comonomer. This suggested that the high-temperature state can be described as a columnar mesophase corresponding to the well established case of the poly(dipentylsilylene). Correlated to this transition, the copolymers also showed thermochromic behavior at low temperatures. The materials could be oriented by shearing in the mesophase, which was demonstrated by polarized optical microscopy, polarized IR spectroscopy and UV spectroscopy.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1997.010480805
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of polydipentylsilylenes and -siloxanes containing chiral groups (1997)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 48 (1997), S. 438-445 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polydipentylsilylene and -siloxane copolymers, containing bis[(S)-(+)-2-methylbutyl]silane units have been synthesized. Thermal analysis demonstrated for both types of copolymers that crystallization was hindered on incorporation of the 2-methylbutyl groups. Optical rotation measurements in various solvents yielded a much stronger optical activity of the polysilylene copolymers, compared to the polysiloxanes. This effect has been explained by the formation of a chiral supramolecular structure in the case of the polysilylenes. The measurements have indicated that the solvent quality can be employed to enhance the formation of this structure at relatively low 2-methylbutyl contents.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1997.010481004
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  • 8
    Electronic Resource
    Electronic Resource
    Stabilization of colloidal palladium particles by a block copolymer of polystyrene and a block containing amide sidegroups (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 481-484 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A block copolymer of polystyrene and poly(tert-butylmethacrylate) was prepared by anionic polymerization. The ester groups of the poly(tert-butylmethacrylate) were hydrolyzed, after wich the remaining carboxyl groups were reacted with pyrrolidine. The resulting block copolymer with amide sidegroups was used for stabilization of a palladium colloid in toluene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471102
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  • 9
    Electronic Resource
    Electronic Resource
    Darstellung und Struktur von α-CrPO4. Beiträge zum thermischen Verhalten von wasserfreien Phosphaten. I (1986)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 543 (1986), S. 111-116 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions on the Thermal Behaviour of Anhydrous Phosphates. I. Preparation and Structure of α-CrPO4By a chemical transport reaction (1100°C → 1000°C) using chlorine as transporting agent we obtained dark-green, well shaped crystals of α-CrPO4. The compound crystallizes in the space group Imma. The lattice constants are a = 10.403(2), b = 12.898(2), c = 6.299(1) Å. The crystal structure has been determinated from single crystal data and refined to a conventional residual of R = 0.038 (1481 unique reflections, 34 variables). The structure consists of CrO6-octahedra and PO4-tetrahedra. Especially remarkable are pairs of edge sharing CrO6-octahedra which are connected with two PO4-tetrahedra at opposite edges. Parallel to the a- and b-axis are large channels extending through the whole structure.
    Notes: Durch chemischen Transport mit Chlor als Transportmittel (1100°C → 1000°C) erhielten wir dunkelgrüne, gut ausgebildete Kristalle von α-CrPO4. Die Substanz kristallisiert in der Raumgruppe Imma mit a = 10,403(2), b = 12,898(2), c = 6,299(1) Å. Die Kristallstruktur wurde aus Einkristalldaten bestimmt (R = 0,038; 1481 Fo, 34 Variable). α-CrPO4 ist aus CrO6-Oktaedern und PO4-Tetraedern aufgebaut. Bemerkenswert sind kantenverknüpfte CrO6-Oktaeder-Paare, die an gegenüberliegenden Kanten noch mit zwei PO4-Tetraedern verbunden sind. Parallel zur a- und b-Achse verlaufen größere Kanäle.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19865431214
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  • 10
    Electronic Resource
    Electronic Resource
    Über LaCo2P2 und andere Neue Verbindungen mit ThCr2Si2- und CaBe2Ge2-Struktur (1985)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 527 (1985), S. 73-84 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On LaCo2P2 and Other New Compounds with ThCr2Si2- and CaBe2Ge2-Type StructureThe compounds MCo2P2 (M = La, Ce, Pr, Nd, Sm, Th, U), MFe2P2 (M = La, Ce, U), and ThCo2As2 were prepared for the first time. Structure determinations from single crystal X-ray data of LaCo2P2 (R = 0.011; 325 F-values), CeCo2P2 (R = 0.023; 160 F), PrCo2P2 (R = 0.044; 441 F), LaFe2P2 (R = 0.024; 511 F), and CeFe2P2 (R = 0.016; 183 F) with 11 variable parameters each resulted in atomic positions within the range of the ThCr2Si2-type. The powder patterns of ThCo2P2, and ThCo2As2 show superstructure reflections indicating a CaBe2Ge2-type structure. The other compounds can be assigned to the ThCr2Si2-type. Chemical bonding of these can be rationalized by a simple band structure model where bonding transition metal - transition metal interactions are important.
    Notes: Die Verbindungen MCo2P2 (M = La, Ce, Pr, Nd, Sm, Th, U), MFe2P2 (M = La, Ce, U) und ThCo2As2 wurden erstmals synthetisiert. Strukturbestimmungen aus Röntgen-Einkristalldaten von LaCo2P2 (R = 0,011; 325 F-Werte), CeCo2P2 (R = 0,023; 160 F), PrCo2P2 (R = 0,044; 441 F), LaFe2P2 (R = 0,024; 511 F) und CeFe2P2 (R = 0,016; 183 F) mit jeweils 11 variablen Parametern ergaben Atompositionen innerhalb der Breite des ThCr2Si2-Typs. Die Pulveraufnahmen von ThCo2P2, UCo2P2 und ThCo2As2 zeigen Überstrukturreflexe entsprechend der CaBe2Ge2-Struktur. Die übrigen Verbindungen können alle dem ThCr2Si2-Strukturtyp zugeordnet werden. Für diese Verbindungen wird ein einfaches Bandstrukturmodell diskutiert, bei dem bindende Wechselwirkungen zwischen den Übergangsmetallatomen eine wesentliche Rolle spielen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19855270807
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