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  • 1
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the configuration at the C=N double bond and of substitution at each site of an amidino group on the effect of substituents at the other two sites has been studied by ab initio 3-21G optimization for eight derivatives of formamidine (all in the cis configuration at the C=N double bond) with up to three fluorine substituents in different combinations, and the corresponding formamidinium cations (protonated at the imino nitrogen). The results were compared with those obtained previously for an identical set of compounds but in the trans configuration. The differences between the influence of substitution at various sites in cis and trans isomers of amidines on basicity, tautomerization, and the geometry of the molecules are discussed.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 2012-2020 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: tert-Butylation of Biphenyl; Determination of the Structure of Reaction Products by Means of Independent SynthesesThe Friedel-Crafts alkylation of biphenyl with tert-butyl chloride in carbon disulfide using aluminium trichloride as catalyst leads to the formation of only 9 of the 209 theoretically possible tert-butylbiphenyls, namely 3- and 4-tert-butylbiphenyl, 3,5-, 3,3′-, 3,4′- and 4,4′-di-tert-butyl-biphenyl, 3,3′,5-, and 3,4′,5-tri-tert-butylbiphenyl as well as 3,3′,5,5′-tetra-tert-butylbiphenyl. These have been separated by gas chromatography and identified by means of independently synthesized compounds in combination with GC-MS determinations. Five of these compounds have been prepared for the first time.
    Notes: Die Friedel-Crafts-Alkylierung von Biphenyl mit tert-Butylchlorid in Schwefelkohlenstoff liefert bei Verwendung von AICI3 als Katalysator nur 9 von theoretisch 209 möglichen tert-Butylderivaten, nämlich 3- und 4-tert-Butylbiphenyl, 3,5-, 3,3′-, 3,4′- und 4,4′-Di-tert-butylbiphenyl, 3,3′,5- und 3,4′,5-Tri-tert-butylbiphenyl sowie 3,3′,5,5′-Tetra-tert-butylbiphenyl. Diese wurden gaschromatographisch getrennt und ihre Strukturen durch unabhängige Synthesen in Kombination mit GC-MS-Untersuchungen gesichert. Fünf von ihnen waren noch nicht bekannt.
    Additional Material: 1 Ill.
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  • 3
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 4
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 5
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The complete molecular structure of biphenyl, characterized by 12 independent parameters, has been derived by ab initio gradient techniques using a STO-3G basis set for coplanar, perpendicular, and minimum energy conformations with the constraint of planar phenyl ring units and a C2 symmetry axis along the CC interring bond. The minimum torsional angle obtained was φ = 38.63° with torsional energy barriers of 8.59 and 10.04 kJ/mol for φ = 0° and φ = 90°, respectively.
    Additional Material: 5 Tab.
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  • 6
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Different highly accurate experimental determinations of molecular structures (ED: rg and r0α, MW: r0, rs, and rz, and X-ray distances) of 14 unstrained hydrocarbons have been linearly correlated with corresponding self-consistent field Hartree Fock (SCF HF) ab initio full gradient-optimized structures. From the eight applied basis sets (STO-3G, STO-6G; 3-21G, 4-31G, 6-31G, 6-311G; 6-31G*, and 6-31G**) the 6-31G basis set, although not best regarding total energies, yields statistically the most precise regression equation, which allows the prediction of ED rg CC distances as reliable as the best experimental determinations. Surprisingly the accuracy of all calculated CC distances (measured as difference Δ between calculated CC distances and experimental ED rg values) depends linearly on bond distances, with the largest deviations being observed for triple bonds. This seems to be a clear indication of different influences of correlation effects on calculated geometries which are neglected in the applied HF treatment. The linear regression equations presented here allow the prediction of any kind of experimental CC distance parameters for each of the eight basis sets considered. Even experimentally unknown re CC distances may be predicted from these single determinantal HF optimizations.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 1605-1615 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese of Mesityl-substituted AzulenesThe five position isomer mesityl-substituted azulenes 1-5 have been prepared for the first time. 1- and 5-mesitylazulene (1 and 4) have been obtained by addition of mesityl-Li to appropriate ketonic precursors followed by dehydration and dehydrogenation with sulfur. 2- and 6-mesitylazulene (2 and 5) have been prepared by Hafner syntheses from correspondingly substituted precursors, and 4-mesitylazulene (3) was synthesized via nucleophilic addition of mesityl-Li to azulene. The physical properties as well as electronic spectra are compared and discussed.
    Notes: Die fünf stellungsisomeren mesitylsubstituierten Azulene 1-5 wurden erstmals dargestellt. 1- und 5-Mesitylazulen (1 und 4) wurden durch Addition von Mesityl-Li an geeignete Ketonvorstufen mit nachfolgender Dehydratisierung und Dehydrierung mit Schwefel erhalten. 2- und 6-Mesitylazulen (2 und 5) wurden durch Hafner-Synthesen aus geeignet mesitylsubstituierten Vorstufen dargestellt, und 4-Mesitylazulen (3) wurde über nucleophile Addition von Mesityllithium an Azulen erhalten. Die physikalischen Eigenschaften und Elektronenspektren dieser Verbindungen werden vergleichend diskutiert.
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  • 9
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Simple Synthesis of Indoles and of Corresponding 3(2H)-Indolone Derivatives, Monosubstituted at the Benzene Ring, as Synthetic Precursors of Natural CompoundsApplication of a specific BCl3-catalyzed ortho-chloroacetylation of the monosubstituted primary anilines 2a-e with chloroacetonitrile, as a variant of the Houben-Hoesch reaction, leads to the corresponding 2-amino-α-chloroacetophenones 3a-g. These may be reduced and cyclized to yield the indoles 4a-g or, after acylation to 5a-g and 7a, b converted by base-catalyzed dehydrochlorination into the 1-acyl-3(2H)-indolones 6a-g and 8a, b.
    Notes: Die monosubstituierten primären Aniline 2a-e werden durch BCl3-katalysierte ortho-spezifische Chloracetylierung mit Chloracetonitril in einer Variante der Houben-Hoesch-Reaktion in die entsprechenden 2-Amino-α-chloracetophenone 3a-g übergeführt. Diese können durch reduktive Cyclisierung in die entsprechenden Indole 4a-g oder nach Acylierung zu 5a-g und 7a, b durch basenkatalysierte HCl-Abspaltung in die 1-Acyl-3(2H)-in-dolone 6a-g und 8a, b umgewandelt werden.
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  • 10
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Improved full ab initio optimizations of the molecular structure of biphenyl in twisted minimum energy, coplanar, and perpendicular conformations by use of Poles's GAUSSIAN 82 program have been performed in the 6-31G basis set. These lead to geometries and energies of much higher reliability than our earlier STO-3G results. The torsional angle Φmin obtained now is 45.41° in close agreement with the recent experimental value of 44.4° ± 1.2°. Calculated CC distances may be converted to experimental ED rg-values by means of independently determined linear regression correlations with very high statistical confidence, although they agree better with experimental x ray data for coplanar biphenyl without this correction. Calculated intramolecular angles are very similar for both STO-3G and 6-31G basis sets. The calculated torsional energy barrier towards Φ = 90° (ΔE90) is 6.76 kJ/mol in close agreement with the experimental-31G value of 6.5 ± 2.0 kJ/mol. For coplanar biphenyl with D2h-symmetry the calculated torsional energy barrier ΔE0 is 13.26 kJ/mol which is surprisingly much higher than the experimental value of 6.0 ± 2.1 kJ/mol. This discrepancy could not be resolved by optimizations assumed for two kinds of distortions of planarity of orthohydrogens from the molecular plane of the coplanar carbon atoms. But for the twisted minimum energy conformation asymmetric bending of ortho-H atoms lead to a torsional angle Φmin = 44.74° together with a dihedral angle towards ortho-H of 1.22°, and consequently even to an increase of torsional energy barriers to ΔE0 = 13.51 and ΔE90 = 6.91 kJ/mol.
    Additional Material: 1 Ill.
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