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  • 1
    Electronic Resource
    Electronic Resource
    Photochemistry of 9,10-Dicarbonyl-9,10-dihydroanthracene - A Source of 9,10-Dehydroanthracene? (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 57-60 
    Details
    ISSN: 1434-193X
    Keywords: Benzyne ; Dehydroanthracene ; Matrix isolation ; Photochemistry ; Bergman reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -9,10-Didehydroanthracene (1) is an interesting derivative of p-benzyne that has been subject of several studies. In contrast to an earlier report, the photochemical decarbonylation of 9,10-dicarbonyl-9,10-dihydroanthracene (2) does not lead to 1 but rather to the ring-opened ene-diyne 4. The key intermediate for this reaction is keto carbene 7 which is formed by monodecarbonylation of 2. Carbene 7 is labile towards visible-light irradiation and easily looses the second CO molecule to give 4. Carbene 7 and diyne 4 are characterized by IR and UV/Vis spectra, the IR spectra are compared to calculations at the B3LYP/6-31G(d,p) level of theory.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Flash Vacuum Pyrolysis and Photolysis of 3,3,5,5-Tetramethylpyrazolin-4-one - A Matrix Isolation Study (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 91-98 
    Details
    ISSN: 1434-193X
    Keywords: Cyclopropanone ; Allene oxide ; Matrix isolation ; Photochemistry ; Flash vacuum thermolysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The flash vacuum pyrolysis of 3,3,5,5-tetramethylpyrazolin-4-one (4) with subsequent trapping of the products in argon at 10 K results in the formation of a complex product mixture with tetramethylcyclopropanone (5) as one of the minor constituents. The 193 nm photochemistry of matrix-isolated 4 is much cleaner, yielding cyclopropanone 5 and allene oxide 9 as the major products. The reaction of tetramethylallene 13 with oxygen atoms yields the same product mixture of 5 and 9 and thus provides an independent route to these species. The experimental IR spectra of 5 and 9 are in good agreement with the results from DFT calculations.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99377_s.pdf or from the author.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Photochemical Hydrogen Migration in Methylanthronylidenes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1005-1009 
    Details
    ISSN: 1434-193X
    Keywords: Hydrogen migration ; Anthronylidene ; Quinone methide ; Matrix isolation ; Photochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The photochemistry of 4-methyl-9,10-diazoanthrone (7a) and 1,4-dimethyl-9,10-diazoanthrone (7b) was investigated in argon matrices at 10 K. Visible-light irradiation results in the formation of the anthronylidenes 5a and b, respectively, which were identified by oxygen trapping, by comparison of the IR and UV/Vis spectra with that of the parent anthronylidene 6, and by comparison of the IR spectrum with that calculated by DFT methods. The carbenes 5 are thermally stable under the conditions of matrix isolation; however, irradiation with visible or UV light results in the rearrangement to the quinone methides 10a and b.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Photochemistry of [2.2]Paracyclophan-enes  -  a Matrix-Isolation Study (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 2039-2043 
    Details
    ISSN: 0947-3440
    Keywords: Cyclophan-ene ; Photochemistry ; Diradicals ; Matrix isolation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The UV photolysis of [2.2]paracyclophan-ene (3) and benzo-[2.2]paracyclophan-ene (4), matrix-isolated in argon at 10 K, results in the cleavage of the ethano bridge and formation of compounds 5 and 8, respectively. The IR and UV/Vis spectra are compared with p-xylylene and the benzyl radical as models for a quinoid or diradicaloid structure. The absence of an ESR signal reveals a singlet ground state for these compounds. Remarkable is a sharp absorption in the red part of the visible spectrum which is not observed in the case of p-xylylene or the benzyl radical. The electronic structure can be described as quinoid with a substantial amount of diradicaloid character.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961214
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