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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 310-316 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: EPR-Investigations on the Photolysis of Halogenated Organic Compounds I. Pure Halogenated Compounds (CBr4, CHBr3, CCl4 and CHCl3)EPR-spectra of CBr4, CHBr3 and CDBr3, exposed to u.v.-light and γ-rays respectively, are presented. They are discussed and compared with the results of the photolysis of CH2Br2, CH3Br and CCl4, CHCl2, CH2Cl2 and CH3Cl. Under stationary conditions at 77K it was possible to identify paramagnetic species like \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CBr}_4\,^{_{\bar.}} $\end{document}, ·CBr3, ·CH3, ·C2H5, ·CCl3 and trapped electrons.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 317-327 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: EPR-Investigations on the Photolysis of Halogenated Organic Compounds. II. CHBr3 and CBr4 in Glassy and Polycrystalline MatricesPhotolysis of CHBr3, CDBr3 and CBr4 in glassy and polycrystalline matrices (alcohols, diethylether, benzene derivatives and KBr) at T ≥ 77 K yields stationary e.p.r.-spectra in the range of effective g-factor from 2.2 to 1.9. By comparison of the spectra of CHBr3 and CDBr3, exposed to γ-rays and u.v. light respectively, and the spectra of these compounds in matrices it was shown that the photolysis in matrices produces the species \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CBr}_4\,^{_{\bar.}} $\end{document}, ·CBr3 and α-Br-radicals from the halogenated compounds and HĊO, ·CH3, CH3ĊHOH, RĊHOH, and ·C2H5 from the matrix. Photolysis of halogenated compounds in CH3OH and CD3OD yields only HĊO and ·CH3 together with a very small amount of bromine-containing radicals. In all other investigated matrices the concentration of bromine containing species is controlled by physical and chemical properties of the matrix. Time development of the \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CBr}_4\,^{_{\bar.}} $\end{document}-radical and of those generated from the matrix is different and gives insight into the complex photoreaction in solid matrices.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 453-460 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photochemistry of Acylazides. I. Photo- and Thermochemistry of 5-Azidocarbonyldibenz[b,f]azepine and its DimerThe reactions of the title compounds, two new carbamoylazides, by photoexcitation and in the ground state, respectively, were investigated. The photochemistry of compounds 1 und 2 differs from that of other heterocycles of the same type and is determined by the azido group. They exhibit the three known kinds of reactions of carbamoylazides via singlet and triplet nitrene, respectively, and the Curtius-rearrangement forming an intramolecular insertion product 6, dibenz-[b,f]azepine 4 and the isocyanate. Products from triplet nitrenes are lacking in the photoreaction of the dimeric azide 2.The decomposition of the azide 1 can be sensitized by triplet energy transfer. Surprisingly, the isocyanate is also formed by triplet sensitization.Photoexcited pyrene reacts with 1 via electron transfer yielding rearrangement and triplet products, respectively. In contrast to diphenylcarbamoylazide, the reaction pathway of the thermally excited compounds leads to nitrene products mainly.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 104-112 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electrochemistry of Organic Cations. Arylsubstituted Tropylium SaltsThe electrochemical behaviour of some mono- and diarylsubstituted tropylium perchlorates in acetonitrile was investigated and is discussed in connection with their u. v.-vis absorption spectra.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 925-932 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: About the Deactivation Behaviour of Photoexcited Aryltropyliumions. II. Fluorescence Quenching of AryltropyliumionsThe properties of aryltropyliumions in the excited singlet state were studied. These ions are very strong acceptors. So the fluorescence is quenched by aromatic donors. The rates of fluorescence quenching depend on the ionization potential of the donor. This fact is discussed in terms of mechanisms derived by WELLER et al. The results were related to the light stability of aryltropyliumions.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 569-578 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Aryltropylium salts exhibit an unusually effective self quenching of fluorescence in dependence on their concentration in dichlòromethane. The quenching process is investigated by static and time resolved fluorescence measurements. The observed biexponential fluorescence decay is interpreted by the emissions of ion pairs and free cations. The rate constant of fluorescence quenching by formation ion pair is two orders of magnitude greater than the diffusion constant.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 39 (1889), S. 366-373 
    ISSN: 0021-8383
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 15N-CIDNP. spectra recorded during the reaction of diazonium cations with OH- in weakly alkaline aqueous solutions show that the dediazoniation is at least partially homolytic. The polarizations observed for the diazonium and trans-diazotate ions can be explained by reaction proceeding via a cage involving diazenyl and diazotate radicals using Kaptein's rules and simple intensity considerations.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 726 (1969), S. 188-200 
    ISSN: 0075-4617
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: p-Xylylenes*). Valence Tautomerism of Unsaturated SystemsIn the dehalogenation of 7a the saturated solvent containing tetramer 9a is isolated instead of the expected quinoid p-xylylene 8a. If energy is applied to the system (heat or mechanical pressure), compound 9a is cleaved to a slight extent and turns blue both in the solid state and in solution. In solution the monomeric fraction occurs mainly as the quinoid p-xylylene 8a; however, the paramagnetism of the blue violet crystals suggests that the twisted biradicals 10a are formed. By suitable substitution of the dibromide 7a it can be shown that the remarkable behaviour of p-xylylene 8a is due, in the main, to the steric hindrance of the hydrogen atoms on C-1 and C-2′ together with the tendency of the quinoid system to aromatize.
    Notizen: Bei der Enthalogenierung von 7a wird anstelle des erwarteten chinoiden p-Xylylens 8a das gesättigte solvenshaltige Tetramere 9a isoliert. Durch Energiezufuhr (Erhitzen oder mechanischer Druck) wird 9a sowohl in festem Zustand als auch in Lösung in geringem Umfang unter Blauviolettfärbung gespalten. Während in Lösung die monomeren Bruchstücke vorwiegend als chinoides p-Xylylen 8a vorliegen, spricht der Paramagnetismus der blauvioletten Kristalle dafür, daß hier verdrillte Biradikale 10a gebildet werden. Durch geeignete Substitution des Dibromids 7a läßt sich zeigen, daß das bemerkenswerte Verhalten des p-Xylylens 8a wesentlich auf die sterische Hinderung der Wasserstoff-Atome an C-1 und C-2′ im Zusammenwirken mit der Aromatisierungstendenz des chinoiden Systems zurückzuführen ist.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 154 (1870), S. 93-130 
    ISSN: 0075-4617
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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