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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1303-1310 
    ISSN: 1434-193X
    Keywords: Ketones ; Alkynes ; Cyclic voltammetry ; Photoelectron spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The fourteen-membered ring of 7,7,12,12-tetramethyl-1,4-dioxacyclotetradecane-8,9,10,11-tetrone (4) was built up from 1,2-bis(2′-chloroethoxy)ethane, two units derived from isobutyric acid and acetylene. Key intermediates were 2,2,11,11-tetramethyl-5,8-dioxadodecane-1,12-diol (8), 7,7,12,12-tetramethyl-1,4-dioxa-9-cyclotetradecyne-2,8-diolprotected by one tetrahydropyran group (15), and 8,11-dihydroxy-7,7,12,12-tetramethyl-1,4-dioxacyclotetradecane-9,10-dione (18). X-ray investigation on single crystals of the (R,S) isomer 18a revealed a transannular interaction between the dioxaethane bridge and the dicarbonyl moiety. Calculations (HF/6-31G*) on 4 predict relatively short distances between the oxygen atoms of the dioxyethane bridge and the (CO)4 part. Investigations by means of cyclic voltammetry, PE and UV/Vis spectroscopy on 4 reveal an interaction between the dioxaethane bridge and the (CO)4 group.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Stelladiones ; Photoelectron spectroscopy ; Calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tricyclo[3.3.0.03,7]octane-2,4-dione (2,4-stelladione, 3), tricyclo[3.3.0.03,7]octane-2,6-dione (2,6-stelladione, 4), and 2-oxotricyclo[3.3.0.03,7]octane-6-thione (5) were synthesized. Key steps in the procedures were a Paterno-Büchi reaction followed by an oxetane splitting with a strong base. Structure analysis on single crystals of 4 and 5 revealed long central C-C bonds (1.59 Å) of the stellane skeleton. The He(I) photoelectron spectra of 3, 5, and 4-methylenetricyclo-[3.3.0.03,7]octan-2-one (9) were recorded and interpreted on the basis of quantum-mechanical calculations (HF-SCF, 6-31G* basis). The large energy difference between the first PE bands of 3 (0.8 eV) is due to a strong interaction between the lone pairs on the oxygen atoms and the σ frame.
    Type of Medium: Electronic Resource
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