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  • Inorganic Chemistry  (4)
  • 1985-1989  (4)
  • 1975-1979
  • 1985  (4)
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  • 1985-1989  (4)
  • 1975-1979
Year
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 4281-4284 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Structure and Stereoselectivity of 2-Norbornen-7-yl Radicals and CarbenoidsReduction of 7,7-diiodonorbornene (1) with Grignard reagents proceeds via the 7-iodo-2-norbornen-7-yl radical 2. From the observed syn-stereoselectivity, the absence of π-delocalization in 2 is inferred. This result agrees with the existence of an equilibrium mixture of two classical pyramidal structures (2a and 2b), in which the syn-isomer 2a predominates. The reaction of 1 with methyllithium takes place with anti-stereoselectivity; this fact proves that the anti-carbenoid 4b-M is more stable than the syn-isomer.
    Additional Material: 1 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 2557-2560 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectivity in the Reaction of Carbocations with Nucleophiles, 2. Solvolytic Mechanisms of 7-Norbornyl TrifluoromethanesulfonatesThe reactions of 7,7-bis(trifluoromethylsulfonyloxy)norbornane (4) with several metal cyanides in dipolar aprotic solvents are studied. The results obtained (Table 1) lead to the conclusion that the solvolysis of 7-substituted 7-norbornyl trifluoromethanesulfonates takes place either according to a kc mechanism or with fission of the S — O bond. In no instance is a C — O fission following an SN2 mechanism to be expected. - The selectivity of the reaction of the intermediate carbocations with nucleophiles cannot be explained by means of N+ correlations nor by the reactivity-selectivity relationship, but can be rationalized according to the HSAB principle.
    Additional Material: 1 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 1282-1288 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanism of the Reaction of Trifluoromethanesulfonic Anhydride with Ketones: Reaction with CamphorReaction of camphor (1) with trifluoromethanesulfonic anhydride (Tf2O) in the absence of base yields a mixture of 2,2-bis(trifluoromethylsulfonyloxy)camphane (9), 1,2-bis(trifluoromethylsulfonyloxy)-endo-isocamphane (10), and 2,4-bis(trifluoromethylsulfonyloxy)-endo-isocamphane (11). The ratio of these compounds depends on the reaction temperature. 9, 10, and 11 could not be isolated because, during the final aqueous treatment, they undergo hydrolysis leading to 1, 1-camphenyl triflate (2), and 4-camphenyl triflate (3). In the presence of 2,6-di-tert-butyl-4-methylpyridine (DTBMP) 2 is the main reaction product. The reaction rate is independent of the base concentration. It can be inferred that the base only neutralized the trifluoromethanesulfonic acid (TfOH), without reaction with Tf2O. - Reaction of 2 with TfOH in dichloromethane takes place with addition and Nametkin rearrangement. The ratio of these reactions depends on the reaction temperature. No rearrangement products are obtained in the reaction of 1 with TfOH. The reaction paths for the reaction of 1 with Tf2O are compared with those for other ketones, and some conclusions on the electronic requirements of the Nametkin rearrangement are inferred.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 528 (1985), S. 183-190 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Das System CoSeO4-NiSeO4—H2O bei 30°C. Kristallstruktur des CoSeO4 · 5 H2OEs wird das System CoSeO4—NiSeO4—H2O bei 30°C untersucht. Die Kristallwerden aus wäßriger Lösung durch langsames Eindampfen erhalten. Die gefundenen Phasen sind CoSeO4 · 5 H2O und NiSeO4 · 6 H2O; CoSeO4 · 6 H2O wird dann gefunden, wenn die Kristallisation der Co-Verbindung in Gegenwart von Ni erfolgt. Diese drei Phasen zeigen einen begrenzten Ersatz des Metalls auf Grund von Röntgenpulverdaten. Die Kristallstruktur des CoSeO4 · 5 H2O ist triklin, a = 6.435(1), b = 10,703(2), c = 6,220(1) Å, α = 98,71(1), β = 109,60(2), γ = 75,54(1)°, P1, Z = 2. Verfeinerung bis zu R = 0,032 für alle beobachteten Reflexe. Die Kristallstruktur ist isostrukturell zu CuSO4 · 5 H2O und besteht aus Ketten von Co(H2O)4-Ionen parallel zu [110], die brückengebunden über die SeO4-Anionen sind. Das fünfte Wassermolekül wirkt als Puffer.
    Notes: A study of the system CoSeO4—NiSeO4—H2O at 30°C has been carried out. Crystals were obtained by slow evaporation from a water solution. The identified phases were CoSeO4 · 5 H2O and NiSeO4 · 6 H2O, but CoSeO4 · 6 H2O is identified when the crystallization of Co compound is carried out in presence of Ni. The three phases show a limited replacement of metal according to X-ray powder results. The crystal structure of CoSeO4 · 5 H2O has been solved, the come pound is triclinic, a = 6.435(1), b = 10.703(2), c = 6.220(1) Å, α = 98.71(1), β = 109.60(2), γ = 75.54(1)°, P1, Z = 2. Refinement was terminated at R = 0.035 for all observed reflections. The crystal structure is isostructural to CuSO4 · 5 H2O and consists of Co(H2O)4 ions chains parallel to [110] μ-linked by the SeO4. The fifth water molecule acts as buffer.
    Additional Material: 3 Ill.
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