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  • 1
    Electronic Resource
    Electronic Resource
    Electron transfer from trialkyltin radicals to nitrosugars: the synthesis of C-glycosides with tertiary anomeric carbon atoms (1985)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 107 (1985), S. 4332-4333 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00300a043
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of .delta.-lactones via radical carbon-carbon bond formation using chiral radical precursors (1986)
    s.l. : American Chemical Society
    The @journal of organic chemistry 51 (1986), S. 3726-3729 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00369a039
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  • 3
    Electronic Resource
    Electronic Resource
    Electron spin resonance spectroscopic investigation of carbohydrate radicals. 4. 1,2-Acyloxyl migration in pyranosyl radicals (1988)
    s.l. : American Chemical Society
    The @journal of organic chemistry 53 (1988), S. 4364-4369 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00253a032
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  • 4
    Electronic Resource
    Electronic Resource
    Radical addition to amide-substituted alkenes: stereoselective intermolecular radical additions (1989)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 111 (1989), S. 8311-8312 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00203a060
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  • 5
    Electronic Resource
    Electronic Resource
    Einfluß der Substituenten auf Aktivierungsenthalpie-,-entropie und -volumen beim Zerfall organischer Perester (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 240-245 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Influence of Substituents on the Enthalpy, Entropy and Volume of Activation in the Decomposition of Organic PerestersThe influence of the ester group on the decomposition of organic peroxides was studied on peresters of the pivalic and neodecanoic acid with tert-butyl, tert-amyl, 1-methyl-1-propylpentyl and 1,1,4-trimethylpentyl groups at temperatures of 393 to 473 K and pressures up to 3000 bar using a flow method. As expected the half-live times decrease with increasing temperature and increase with rising pressure. With increasing bulkiness of the substituents the rates of decomposition as well as the enthalpies of activation increase. This surprising fact can be explained by the simultaneous increase of the entropies and the volumes of activation.
    Notes: Der Einfluß der Estergruppe auf den Zerfall organischer Peroxide wurde an Perestern der Pivalin- und der Neodecansäure mit tert-Butyl-, tert-Amyl-, 1-Methyl-propylpentyl- sowie 1,1,4-Trimethylpentylresten bei Temperaturen von 393 bis 473 K und Drücken bis 3000 bar in einer Strömungsapparatur untersucht. Die Zerfallshalbwertszeiten nehmen erwartungsgemäß mit steigender Temperatur stark ab und mit steigendem Druck zu. Mit zunehmender Größe der Substituenten steigen sowohl die Zerfallsgeschwindigkeiten als auch die Aktivierungsenthalpien. Dieser überraschende Effekt kann durch die Vergrößerung der Aktivierungsentropie und des Aktivierungsvolumens erklärt werden.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180123
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  • 6
    Electronic Resource
    Electronic Resource
    Zur Selektivität von σ-Radikalen (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 1291-1300 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Selectivity of σ-RadicalsThe σ-radicals 1-3 can be generated by reduction of alkylmercuric salts 5-7 with NaBH4. Their reactions with electronpoor alkenes 8 lead to CC-bond formation products 9-11 (Table 1). Kinetic measurements show that σ-radicals are as selective as π-radicals in alkene competition systems (Table 2).
    Notes: Die σ-Radikale 1-3 können durch Reduktion der Alkylquecksilbersalze 5-7 mit NaBH4 erzeugt und von elektronenarmen Alkenen 8 zu den CC-Verknüpfungsprodukten 9-11 abgefangen werden (Tab. 1). Konkurrenzkinetische Messungen zeigen, daß die σ-Radikale in Additionsreaktionen mit Alkenen die gleiche Selektivität besitzen wie π-Radikale (Tab. 2).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861190418
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  • 7
    Electronic Resource
    Electronic Resource
    Experimental and theoretical studies on the mechanism of 1,2-migration of vinyl and formyl substituents in free radicals (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 3528-3535 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Experimentelle und theoretische Untersuchungen zum Mechanismus der radikalischen 1,2-Umlagerung von Vinyl- und FormylgruppenDie Umlagerungen von Vinyl- und Formylgruppen vom Typ X=CH — CMe2 — ĊH2 → ĊMe2 — CH2 — CH=X (X=CH2 oder O) erfolgen mit vergleichbaren Geschwindigkeiten (106 - 107 l/mol · s, 20°C). In Übereinstimmung mit diesen kinetischen Messungen stehen ab-initio-Rechnungen, nach denen für die Grundkörper Aktivierungsenergien von 14.9 (CH2=CH — CH2 — CH2) und 19.2 kcal/mol (O=CH — CH2 — ĊH2) berechnet werden. Die Rechnungen sagen Cyclopropanderivate als Zwischenstufen der Umlagerung voraus.
    Notes: Vinyl and formyl groups undergo rearrangements of the type X=CH — CMe2 — ĊH2 → ĊMe2 — CH2 — CH=X (X=CH2 or O) with comparable rates (106 — 107 l/mol · s, 20°C). This result is in line with high-level ab initio calculations performed on the basic systems, i.e. X=CH — CH2 — ĊH2, which give barriers of activation of 14.9 (CH2=CH — CH2 — ĊH2) and 19.2 kcal/mol (O=CH — CH2 — ĊH2), respectively. The calculations suggest that the rearrangements proceed via cyclopropane-like intermediates.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861191203
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  • 8
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der Denitrierung aliphatischer Nitro-Verbindungen mit Trialkylstannyl-Radikalen. Eine ESR-kinetische Untersuchung (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1183-1190 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Element-Organic Amine/Imine Compounds, XXVIII1). - Polycyclic Phosphorus-Nitrogen Rhenium(I) ComplexesAlkyl(trialkylstannyloxy) nitroxyl radicals 3 have been detected by ESR spectroscopy as intermediates in the denitration reaction of aliphatic nitro compounds with trialkylstannyl radicals (R′=Me, n-Bu), generated photolytically from hexa-n-alkylditins or tri-n-butyltin hydride in benzene solution. In most cases, the additional formation of dialkyl nitroxyl radicals 4 could be observed at prolonged reaction times. The decay kinetics of radicals 3 have been investigated by time-resolved ESR spectroscopy in the temperature range of 248 to 326 K. Alkyl(trialkylstannyloxy) nitroxylradicals generated from tertiary nitro compounds decay by a first- order process, whereas those from secondary and primary nitro compounds follow broken reaction orders 1 n 2. A mechanistic scheme for the reaction of aliphatic nitro compounds with trialkylstannyl radicals is proposed, substantiated by a product study.
    Notes: Bei der Denitrierung aliphatischer Nitro-Verbindungen mit photolytisch aus Hexaalkyldizinn oder Tri-n-butylzinnhydrid in Benzol erzeugten Trialkylstannyl-Radikalen (R′=Me, n-Bu) wurden ESR-spektroskopisch intermediär auftretende Alkyl(trialkylstannyloxy)nitroxyl-Radikale 3 nachgewiesen. Bei längerer Reaktionszeit konnte in den meisten Fällen zusätzlich die Bildung von Dialkylnitroxyl-Radikalen 4 beobachtet werden. Die Kinetik der Abreaktion der Nitroxyle 3 wurde mit Hilfe der zeitaufgelösten ESR-Spektroskopie im Temperaturbereich von 248-326 K gemessen. Während aus tertiären Nitro-Verbindungen erzeugte Alkyl(trialkylstannyloxy)nitroxyle in einer Reaktion 1. Ordnung abreagieren, folgen die aus primären oder sekundären Nitro-Verbindungen erzeugten Vertreter gebrochenen Reaktionsordnungen zwischen Eins und Zwei. Gestützt durch eine Produktanalyse wird ein mechanistisches Schema für die Reaktion aliphatischer Nitro-Verbindungen mit Trialkylstannyl-Radikalen angegeben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200715
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  • 9
    Electronic Resource
    Electronic Resource
    Polar effects in radical addition reactions: Borderline cases (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 2063-2066 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl radicals substituted by one ester or nitrile group are on the borderline between nucleophilic and electrophilic behavior. In addition reactions of these borderline radicals to styrenes, polar effects of both, electron-withdrawing and electron-donating substituents at the alkene, increase the rates. But these polar effects are smaller compared to those of nucleophilic or electrophilic radicals. In consequence, the stability of the radicals formed during the addition of the borderline radicals to styrenes are of major importance for the rate of the reaction.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881211127
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  • 10
    Electronic Resource
    Electronic Resource
    Zum Einfluß sterischer Effekte auf die Selektivität radikalischer CC-Verknüpfung (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 1345-1351 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Influence of Steric Effects on the Selectivity of Radical CC Bond Formation ReactionsBulky substituents R1 and R2 at radical 5 decrease the rate of addition to diethyl fumarate to a larger extent than to methyl acrylate (Table 1). The comparison with H-abstraction, which is only slightly influenced by steric effects, shows that 5e (R2 = t-C4H9) reacts at least 235 times slower with diethyl fumarate than 5a (R2 = CH3) (Table 2). Therefore, the stereoselectivity of cyclic radicals 1 (n = 1, 2) increases if the CC bond formation reaction is carried out with diethyl fumarate instead of methyl acrylate.
    Notes: Sperrige Substituenten R1 und R2 am Radikal 5 verringern die Additionsgeschwindigkeit an Fumarsäure-diethylester stärker als die Additionsgeschwindigkeit an Acrylsäure-methylester (s. Tab. 1). Der Vergleich mit dem von sterischen Effekten nur wenig beeinflußten H-Einfang zeigt, daß 5e (R2 = t-C4H9) mindestens 235mal langsamer mit Fumarsäure-diethylester reagiert als 5a (R2 = CH3) (s. Tab. 2). Deswegen steigt die Stereoselektivität der cyclischen Radikale 1 (n = 1,2) um den Faktor 5-7, wenn bei der CC-Verknüpfungsreaktion Fumarsäureester anstelle von Acrylsäureester eingesetzt wird.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180406
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