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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 426-439 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Stereochemistry of Sigmatropic 1,5-Hydrogen ShiftsAt 250° (S)-cis,trans-3-methyl-7-deutero-octa-4,6-diene (5) rearranges by a non-catalysed first order reaction to a mixture of (R)-trans,cis-3-methyl-7-deutero-octa-3,5-diene (3) and (S)-cis,cis-3-methyl-7-deutero-octa-3,5-diene (4). Therefore the sigmatropic 1,5-hydrogen shift proceeds in this system preferentially by way of a suprafacial transition state, which is at least 8 kcal/mol lower in energy than the antarafacial one.
    Notes: (S)-cis,trans-3-Methyl-7-deutero-octadien-(4.6) (5) lagert sich bei 250° in einer nichtkatalysierten Reaktion erster Ordnung in ein Gemisch aus (R)-trans,cis-3-Methyl-7-deutero-octadien-(3.5) (3) und (S)-cis,cis-3-Methyl-7-deutero-octadien-(3.5) (4) um. In diesem System durchläuft die sigmatrope 1.5-Wasserstoffverschiebung damit bevorzugt einen suprafacialen Übergangszustand, der um mindestens 8 kcal/Mol gegenüber dem antarafacialen Übergangszustand begünstigt ist.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 1655-1658 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2,3-Butatrien durch Diels-Alder RetrogressionThe pyrolysis of 1 leads to indane (6), whereas 2,3, and 4 yield 1,2,3-butatriene (5) by a Diels-Alder-retrogression.
    Notes: Die Pyrolyse von 1 führt zu Indan (6), während 2,3 und 4 unter Diels-Alder-Spaltung zerfallen und 1,2,3-Butatrien (5) liefern.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 1158-1162 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rotational Barrier for the Geometrical Isomerization of cis-and trans-1,4-DimethylbutatrieneThe synthesis of cis(3a) and trans-1,4-dimethylbutatriene (3b) is described. The activation parameters for the mutual interconversion of the geometrical isomers have been determined: Ea = 31.8 ± 0.3 kcal/mol; A= 1.1 × 1013S-1 (ΔH125°C≠ = 31.0 kcal/mol; ΔH125°C≠ = -1.5 cal/grad × mol). The equilibrium constant was found to be K = 1 in the temperature range 100-150°C.
    Notes: Die Synthese von cis-(3a) und trans-1,4-Dimethylbutatrien (3b) wird beschrieben. Für die wechselseitige Umlagerung der geometrischen isomeren wurden Aktivierungsparameter von Ea = 31.8 ± 0.3 kcal/mol und A= 1.1 × 1013 S-1 (ΔH125°C≠ = 31.0 kcal/mol; ΔS125°C≠ = -1.5 cal/Grad × mol) bestimmt. Im bereich von 100-150°C ist die Gleichgewichtskonstante dieser Reaktion K=1.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 102 (1969), S. 811-814 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Synthese von 6.7-Diaza-tricyclo[3.2.2.02.4]nonen-(6) (4) gelingt ausgehend vom Cycloheptatrien-(1.3.5) mit einer Ausbeute von 45%. Bei 25° zerfällt 4 in Cycloheptadien-(1.4) und Stickstoff.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 2923-2933 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoelectron Spectra of Organic Compounds, VIII. 7,8-Dimethylenebicyclo[2.2.2]octa-2,5-diene and Related CompoundsThe photoelectron spectra of vicinal dimethylene derivatives of cyclohexane and cyclohexene bridged by a group with π-, Walsh, or n-orbitals (3-13) are discussed on the basis of a LCMO model within the HMO approximation. The homoconjugative interaction between the semicyclic diene and one other group is only slight; more pronounced effects are observed if an interaction with two other groups is possible, as in the case of 7,8-dimethylenebicyclo[2.2.2]octa-2,5-diene (3) or 5,6-dimethylene-7-oxabicyclo[2.2.1]hept-2-ene (12).
    Notes: Die Photoelektronenspektren von vicinalen Dimethylenderivaten des Cyclohexans und Cyclohexens, die durch eine Gruppe mit π-, Walsh- oder n-Orbitalen überbrückt sind (3-13), werden auf der Grundlage eines LCMO-Modells im Rahmen der HMO-Näherung diskutiert. Die homokonjugative Wechselwirkung zwischen dem semicyclischen Diensystem und einer weiteren Gruppe ist gering; ausgeprägtere Effekte treten auf, wenn wie im Falle des 7,8-Dimethylenbicyclo-[2.2.2]octa-2,5-diens (3) oder des 5,6-Dimethylen-7-oxabicyclo[2.2.1]hept-2-ens (12) eine Wechselwirkung mit zwei weiteren Gruppen möglich ist.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 2171-2175 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Thermolysis of CyclopropylalleneCyclopropylallene (5), whose synthesis is described, rearranges above 300°C to 3-methylene-1-cyclopentene (6). The kinetic parameters of the reaction were determined (Ea = 50.2 ± 0.2 kcal/mole; A = 1.2 × 1014s-1). Thermolysis of the deuterium labeled compound 5a shows that a 4-5 times faster geometric isomerisation 5a → 5b accompanies the rearrangement 5 → 6.
    Notes: Oberhalb von 300°C lagert sich Cyclopropylallen (5), dessen Synthese beschrieben wird, in das 3-Methylen-1-cyclopenten (6) um. Die kinetischen Parameter der Reaktion werden zu Ea = 50.2 ± 0.2 kcal/mol und A = 1.2 × 1014s-1 bestimmt. Durch Thermolyse der deuteriummarkierten Verbindung 5a wird nachgewiesen, daß die Umlagerung 5 → 6 von einer 4-5 mal schneller verlaufenden geometrischen Isomerisierung (5a → 5b) begleitet ist.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 7
    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
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  • 8
    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
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1263-1275 
    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
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 2349-2371 
    ISSN: 0009-2940
    Keywords: Atropisomers ; Inversion barrier ; Lineshape analysis ; Calculations, force field ; Resonance energy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inversion Barriers of ortho,ortho′-Bridged BiphenylsThe syntheses and spectroscopic properties of the ortho,ortho′-bridged biphenyls 2-19 are described. In the case of 5, 15, and 16 the inversion barrier is determined from the temperature dependence of the NMR spectra (lineshape analysis), in the case of 12, 13, and 14 from the temperature of coalescence, and in the case of 2a, 3b, 7, 17, 18, and 19 from the rate of racemization of the optically active compounds. The experimental inversion barriers, including data from the literature, are compared with those calculated using the extended force field (MM2erw). The conformational behavior of the title systems is significantly affected upon transformation into the corresponding dianion salts. The relevant energy terms are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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