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  • 1
    Electronic Resource
    Electronic Resource
    Structures of Tris(donor)-Tris(acceptor)-Substituted Benzenes, 2.Potassium Salts of Trinitrophloroglucinol (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1727-1731 
    Details
    ISSN: 0009-2940
    Keywords: Conformational analysis ; Benzene, donor-acceptor-substituted ; Benzene ring, distortion of ; Hydrogen bonding, intramolecular ; Calculations, AM1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray crystallographic analysis of the mono-, di-, and tri-potassium salts 2b - d of trinitrophloroglucinol (2a) show their benzene rings to become considerably more distorted on successive deprotonation. A parallel increase in C - C, and a decrease in C - O and C - N bond lengths leading to a radialenetype structure is also observed. For 2b, two chemically different molecules are found in the crystal which differ in their hydrogen-bond pattern as well as in their average bond lengths and deviation of their benzene rings from planarity. AM1 calculations show that for 2b,d a multitude of structures, differing widely in the deviation of their benzene cores form planarity, can exist within a small energy range ( 〈 3 kcal/mol). The experimental and computational results are discussed in terms of a model that emphasizes “push-pull” interactions as the main cause for the distortions of the benzene rings in compounds of type 1 and 2.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240810
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  • 2
    Electronic Resource
    Electronic Resource
    Anellation Reactions of Pyranose DerivativesDedicated to Professor Hans Paulsen on the occasion of his 75th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1019-1022 
    Details
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Glycosides ; Cyclizations ; C—C coupling ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The “push-pull”-activated pyranosidulose 1 reacts with acetylacetone and ethyl acetoacetate to give the methyl pyrano-[2′,3′:7,8]pyrano[3,2-D][1,3]dioxin-9-yl ketone 2a and the pyrano[2′,3′:7,8]pyrano[3,2-D][1,3]dioxine-9-carboxylate 2b. Treatment of 1 with 1,3-cyclohexanediones leads to the 1,3-dioxino[5′,4′:3,4]pyrano[3,4-B]chromen-11-ones 4a and 4b. Dialkyl benzo[7,8]pyrano[3,2-D][1,3]dioxine-7,9-dicarboxylates 5a and 5b were obtained by reaction of ulose 1 with dialkyl 3-oxoglutarates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970534
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