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  • 1
    Electronic Resource
    Electronic Resource
    NorbornanesThe IUPAC name for norbornane: 8,9,10-trinorbornane.. Part 21. Bridging strain in norbornyl and oxanorbornyl cations (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1017-1024 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further evidence is presented that the 2-norbornyl cation is stabilized primarily by C(2)-C(6) bridging, and that C(2)-C(7) bridging leads to prohibitive strain. Thus, a comparison of the heats of hydrogenation of nortricyclene 17 and bicyclo[3. 2. 0. 0.2,7]heptane 18 indicates that the strain energy of the latter is ca. 21.5 kcal/mol higher that that of 17. Furthermore, 6-exo-2-oxabicyclo[2. 2. 1]heptyl sulfonates 8 ionize with strong O(2) participation to the bridged oxonium ion 12. In contrast, 2-endo-7-oxabicyclo[2.2.1]heptyl sulfonates 11 ionize without O(7) participation to form the unbridged carbenium ion 15.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710512
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  • 2
    Electronic Resource
    Electronic Resource
    Stereochemie der Bicyclo[2.1.0]pentan-Ringöffnung; Thermolyse von Tricyclo[3.2.0.02,4]heptan-Derivaten (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2717-2737 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereochemistry of the Bicyclo[2.1.0]pentane Ringopening; Thermolysis of Tricyclo[3.2.0.02,4]heptane DerivativesThermolysis of the anti-tricyclic compounds 6, 22 and 34 proceeds preferentially by concerted [σs2+σa2]-reactions and leads to cis,trans-olefines 8, 24 and 37. The rearrangement of the syn-isomers on the other hand seems to be a nonconcerted reaction yielding the diradicals 15, 27 and 36.
    Notes: Die Thermolyse der anti-Tricyclen 6, 22 und 34 erfolgte bevorzugt im Sinne einer konzertierten [σs2+σa2]-Reaktion und führt zu den cis,trans-Olefinen 8, 24 und 37, während für die Umlagerung der syn-Isomeren ein zweistufiger Verlauf über die intermediären Diradikale 15, 27 bzw. 36 wahrscheinlich gemacht wird.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160802
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  • 3
    Electronic Resource
    Electronic Resource
    Rotationsbarrieren gespannter Olefine (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1263-1275 
    Details
    ISSN: 0009-2940
    Keywords: Rotational barriers ; Olefins, strained ; Heat of hydrogenation ; Force-field calculation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rotational Barriers of Strained OlefinesFor the olefins 1-8 heats of formation have been derived from heats of hydrogenation and force-field calculations, respectively. From the kinetics of their geometrical isomerisation the corresponding values for the transition states were obtained. The rotational barriers, which vary by nearly 30 kcal/mol, can be described by a unique torsional potential (65.9 ± 0.9 kcal/mol), which is independent of the degree of substitution, if a correction is made for the steric energy contribution in the ground- and transition-states.
    Notes: Für die Olefine 1-8 wurde durch Hydrierwärme-Messung bzw. Kraftfeld-Rechnung die Bildungsenthalpie der Grundzustände und durch kinetische Analyse der geometrischen Isomerisierung die der Übergangszustände ermittelt. Die um fast 30 kcal/mol variierenden Rotationsenthalpien lassen sich mit einer einheitlichen, vom Substitutionsgrad unabhängigen Torsionsbarriere (65.9 ± 0.9 kcal/mol) beschreiben, wenn um die sterischen Energiebeiträge der Grund- und Übergangszustand korrigiert wird.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220710
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  • 4
    Electronic Resource
    Electronic Resource
    Thermolyse des 1,2,6,7-Octatetraens (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 1934-1946 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolysis of 1,2,6,7-OctatetraeneThe energy profile for the rearrangement of 1 to 3 and 4 and their interconversion by way of 5 is established making use of kinetic methods and by the determination of the heat of hydrogenation of the individual products. For the Cope rearrangement 1 → 4 the competition of concerted and non concerted reaction paths is demonstrated by trapping experiments.
    Notes: Das Energieprofil für die Umlagerung von 1 in 3 und 4 und deren über 5 erfolgende wechselseitige Äquilibrierung wird mit Hilfe kinetischer Methoden und durch Bestimmung der Hydrierwärme der einzelnen Produkte etabliert. Es wird durch Abfangversuche gezeigt, daß die Cope-Umlagerung 1 → 4 über konkurrierende konzertierte und nichtkonzertierte Reaktionswege erfolgt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150523
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  • 5
    Electronic Resource
    Electronic Resource
    Verbotene Reaktionen.  -  [2 + 2]-Cycloreversion starrer Cyclobutane (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1-9 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Forbidden Reactions.  -  [2 + 2] Cycloreversion of Rigid CyclobutanesCyclobutane derivatives, severely restrained from generating noninteractive 1,4-diradicals, are examined thermochemically to provide quantitative evidence to support a forbidden-concerted, antiaromatic mechanism for their [2 + 2] cyclorevision.
    Notes: Die thermochemische Analyse von Cyclobutanderivaten, die keine wechselwirkungsfreien 1,4-Diradikale bilden können, liefert quantitative Evidenz für einen symmetrieverbotenen, konzertierten Mechanismus ihrer [2 + 2]-Cycloreversion mit antiaromatischem Übergangszustand.
    Additional Material: 14 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210102
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrierwärmen, IV. Zur Frage der Homoaromatizität von Norcaradien und Cycloheptatrien (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 217-224 
    Details
    ISSN: 0009-2940
    Keywords: Homoaromaticity ; Resonance energy ; Calculations, force-field ; Heats of hydrogenation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heats of Hydrogenation, IV.  -  Homoaromaticity in Norcaradiene and CycloheptatrieneBy comparison of the heats of hydrogenation of fixed norcaradienes with analogous cyclobutane derivatives and from the difference of experimental heats of formation with values calculated by force-field methods the homoaromatic stabilization of norcaradienes and cycloheptatrienes are calculated and compared with the equilibrium position of the respective valence isomers.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250134
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  • 7
    Electronic Resource
    Electronic Resource
    Zur Energiedelle des orthogonalen Trimethylenmethans. - 1-Methylen-2-phenylcyclopropan-Thermolyse (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2717-2725 
    Details
    ISSN: 0009-2940
    Keywords: Diradicals ; Oxygen trapping ; Energy well ; Heat of formation ; Heat of hydrogenation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Energy Well of the Orthogonal Trimethylenemethane. - 1-Methylene-2-phenylcyclopropane ThermolysisFrom the heat of hydrogenation of 5, the activation enthalpy for the racemization of the title compound, and the oxygen dependance of the trapping rate of the intermediate diradical 8 the energy profile for the degenerate methylene-cyclopropane rearrangement can be constructed, which leads to heats of formation for the triplet and singlet state of the diradical 8 of ΔHf0 · 93.9 and 95.6 kcal mol-1, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261222
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrierwärmen, III. Einfluß von Fluorsubstituenten auf die thermische Umlagerung des Cyclopropansystems (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2508-2515 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Heats of Hydrogenation, III. Influence of Fluoro Substitutents on the Thermal Rearrangement of Cyclopropane SystemsThe influence of the fluoro substituents on the isomerisation of 1,1-difluoro-2-vinylcyclopropane (1) and of cis-1,1-difluoro-2-methyl-3-vinylcyclopropane (11) is demonstrated by kinetic methods and by heat of hydrogenation measurements to be a ground state effect (destabilisation of the cyclopropane by 12-14 kcal/mol). The transition states of the vinylcyclopropane rearrangement of 1 and of the 1,5-homodienyl hydrogen shift of 11 are more or less effected, depending on thier cyclopropane character.
    Notes: Am Beispiel der thermischen Umlagerung des 1,1-Difluor-2-vinylcyclopropans (1) und des cis-1,1-Difluor-2-methyl-3-vinylcyclopropans (11) wird mit Hilfe kinetischer Untersuchungen und durch Bestimmung der Hydrierwärmen gezeigt, daß der Fluorsubstituenteneinfluß in diesen Systemen ein Grundzustandseffekt ist (Destabilisierung des Cyclopropans um 12-14 kcal/mol). Die Übergangszustände der Vinylcyclopropan-Umlagerung von 1 und der 1,5-Homodienyl-wasserstoff-Verschiebung von 11 werden in Abhängigkeit von ihrem Cyclopropancharakter mehr oder weniger stark beeinflußt.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150713
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  • 9
    Electronic Resource
    Electronic Resource
    Bestimmung der Singulett-Triplett-Aufspaltung von Diradikalen mit Hilfe der Sauerstoff-Abfang-Technik (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2047-2051 
    Details
    ISSN: 0009-2940
    Keywords: Diradicals ; Gas-phase kinetics ; Oxygen-trapping technique ; Singlet-triplet splitting ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Determination of the Singlet-Triplet Splitting of Diradicals by Oxygen-TrappingThe diradical 2, generated by thermolysis of 7-methylenebi-cyclo[3.2.0]hept-1-ene (1), can be trapped by oxygen in the gasphase. From the different trapping rates with and without added SF6 the intersystem crossing rates of the diradical have been deduced. From their temperature dependance the singlet-triplet splitting is calculated to be 7.4 kcal mol-1 with the triplet being the ground state. The triplet is protected by an enthalpy barrier of 13.0 kcal mol-1 against recombination of the unpaired electrons (2-tr→1). From the heat of hydrogenation of 1 the heat of formation of 1, 2-s and 2-tr is derived.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240928
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  • 10
    Electronic Resource
    Electronic Resource
    Die Berechnung von Resonanzenergien; das MM2ERW-KraftfeldHerrn Professor Horst Prinzbach zum 60. Geburtstag gewidmet. (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2499-2521 
    Details
    ISSN: 0009-2940
    Keywords: Calculations, force-field ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Resonance Energy Calculation; the MM2ERW Force Field*The additivity of the thermochemical conjugation energy in acyclic systems allows one to extend force-field calculations to conjugated π systems without embarking on quantum-mechanical methods. The approach fails with cyclic delocalized systems, where resonance effects become important. Here the method provides the reference value needed to calculate resonance energies.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241121
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