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  • Chemistry  (16)
  • General Chemistry  (2)
  • 1990-1994  (16)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1777-1779 
    ISSN: 0009-2940
    Keywords: Polar effects ; Radical clock ; Cobaloximes, alkyl ; Radicals, alkyl ; Chlorine abstraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of structurally similar alkyl radicals 1a-c the tertiary 1,1-dimethyl-5-hexenyl radical 1c reacts 30 times faster with carbon tetrachloride than the primary 5-hexenyl radical 1a. The reactivity of the secondary 1-methyl-5-hexenyl radical 1b aligns itself in between the primary and the tertiary radical 1a and 1c. The results indicate that the increasing nucleophilicity of the alkyl radicals is the major factor contributing to the reactivity.
    Additional Material: 1 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1187-1191 
    ISSN: 0009-2940
    Keywords: Cobaloximes, alkyl- ; 5-Hexenyl, cyclization to cyclopentylmethyl ; Radicals, alkyl ; Abstraction of bromine and chlorine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical cyclization and halogen abstraction reactions of secondary alkylcobaloximes 1b and 1d compared to their primary counterparts 1a and 1c show an enhanced reactivity of secondary alkylcobaloximes: Thus, cyclohexylcobaloxime 1d reacts 13 times faster with CCl4 than n1-hexylcobaloxime 1c, 6-hepten-2-yl-cobaloxime 1b rearranges 58 times faster to its cyclopentylmethyl isomer 4b than 5-hexenylcobaloxime 1a. Although free alkyl radicals are reactive intermediates in photolytic conversions of alkylcobaloximes 1 in organic solvents, the presence of BrCCl3 or bromobenzene in photoreactions of primary alkylcobaloximes 1a and 1c seems to cause a more efficient homolytic cleavage of the Co - C bond.
    Additional Material: 3 Tab.
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  • 3
    ISSN: 0009-2940
    Keywords: Alkylrhodoximes ; Radicals, alkyl ; Halogen abstraction ; Carbon-carbon bond formation ; Stereochemistry ; Photoreactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans1-dichlororhodium complex 3. X-ray crystallography of the previously unknown tert1-butylrhodoxime 1k reveals structural features of this tert-s̰1-alkylrhodium compound. Photochemical homolytic cleavage of the Rh - C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 44 (1993), S. 410-415 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Material databaseThis paper describes a new materials database named SWDB. SWDB is the German abbreviation for „Sollwert-Werkstoff-Datenbank“ and should be read as „Specified-Materials-Database“. SWDB is a state of the art user friendly materials database which provides adequate information on standardized and not standardized materials characteristics of solid materials from ferrous and non-ferrous metals and other metallic alloys currently used in engineering practice. Apart from the chemical composition and mechanical-technological properties of metallic materials based on various standards and specifications, the database includes reference to a large number of possible alternative materials in a concise and pregnant form which is transparent and easily accessible for application engineers. The material data are composed on the basis of an absolutely new structured model and are shown as a function of the specified material, product shape, dimension, delivery condition and sampling.SWDB includes additional information on physical properties as well as exhaustive information on heat treatment, hot and cold forming, weldability and hints for application. The SWDB has a dual character: on the one hand it can be operated as an individual and independent database, on the other hand as a satellite database to support the corrosion database within the information system on corrosion and protection, „CORIS“.
    Notes: Die neu entwickelte Sollwert-Werkstoff-Datenbank (SWDB) ist eine benutzerfreundliche Werkstoff-Datenbank, die Informationen über genormte und nicht genormte Werkstoff-Kennwerte massiver, metallischer Werkstoffe bereitstellt. Der Inhalt dieser Datenbank setzt sich zusammen aus Solldaten von ingenieurmäßig gebräuchlichen, massiven Werkstoffen aus Eisen- und Nichteisenmetallen. Neben der chemischen Zusammensetzung und den mechanisch-technologischen Eigenschaften von metallischen Werkstoffen nach verschiedenen Normen und Spezifikationen sind eine Vielzahl möglicher alternativer Werkstoffkandidaten in kurzer, prägnanter und für den Anwender gut einsehbarer Form referiert. Die Daten sind auf der Basis eines völlig neu strukturierten Modells aufgebaut und in Abhängigkeit vom spezifizierten Werkstoff von der Erzeugnisform, der Abmessung, dem Lieferzustand und von der Probennahme wiedergegeben.Außerdem enthält die SWDB zusätzliche Informationen über physikalische Kennwerte sowie zahlreiche Angaben zur Wärmebehandlung, Warm- und Kaltformgebung, Schweißbarkeit und Anwendungshinweise. Die SWDB hat eine doppelte Funktion: einerseits arbeitet sie als unabhängige Datenbank eigenständig, andererseits als Satellit-Datenbank, die die Korrosionsfakten-Datenbank im Informationssystem für Korrosion und Korrosionsschutz „CORIS“ unterstützt.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coronands with 1,2-Dithio-ethene Units. II. Crystal Structures of the Two Crown Thioethers 8,9-Dicyano-8,9-didehydro-7,10-dithia-[12]crown-4 and 11,12-Dicyano-11,12-didehydro-10,13-dithia[15]crown-5The structures of the title compounds have been determined by X-ray analysis. Both thioethers crystallize in the monoclinic system with the following crystal data. Dithia-[12]crown-4: a = 751.7(1), b = 1010.4(1), c = 1639.8(2) pm, β = 95.08(1)°, Z = 4, space group P21/n; dithia[12]crown-5: a = 1169.9(3), b = 916.7(3), c = 1414.1(4)pm, β = 92.51(2)°, Z = 4, space group P21/c. The structures were refined to final R = 0.048 (Rw = 0.031) and 0.040 (0.046), respectively. They are characterized by their structural parameters (bond lengths and angles, torsion angles, l.s. planes) and discussed in special consideration of the ring conformation and the geometric arrangement of the donor atoms.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0170-2041
    Keywords: Aryl coupling, intramolecular ; Biaryls, ester-type bridged, preparation and stereostructure of ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A practicable two-step procedure for the preparation of a series of lactone-type bridged biaryls 7 as favorable substrates for subsequent atropisomer-selective ring-opening reactions is described. Due to the efficiency of the coupling step, which tolerates even a tert-butyl group next to the biaryl axis and avoids problems of regioselectivity, a variety of differently substituted representatives is prepared. These cover a broad range of steric hindrance and thus molecular distortion. The structures are investigated mainly by NMR spectroscopy and X-ray diffraction, showing the lactones 7 to be helically distorted, depending on the size of the residues R.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1003-1007 
    ISSN: 0170-2041
    Keywords: Pyridinethiones ; Pyridinecarbonitriles ; Thieno[2,3-b]pyridines ; Nitriles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The push-pull systems 1 and 7 undergo regioselective cyclization with cyanothioacetamide 2 leading to pyridinethiones 3 and 8. Subsequent S-alkylation affords the alkylthio derivatives 5 and 10. Thieno[2,3-b]pyridines 6 and 11 are formed by using an α-CH-acidic halogen compound as alkylating agent, followed by Thorpe-Ziegler reaction. The cyano group in 6d and 11d can be converted into an imidazoline ring by treatment with 1,2-diaminoethane hydrate and carbon disulfide. Structures are supported by spectral data as well as by X-ray analysis of 5d.
    Additional Material: 1 Ill.
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  • 8
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 0044-2313
    Keywords: Complex compounds ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Crystal Structures and Spectroscopic Investigations of 3d-Transition Metal Complexes with Bicyclo[2.2.1]hept-5-ene-2-endo,3-cis-dicarboxylic Acid and N,N-Donor LigandsThe synthesis of coordination compounds of the general type [MLdam(H2O)3] · 2.5 H2O with M = Mn2+, Co2+, Ni2+; H2L = bicyclo[2.2.1]hept-5-ene-2-endo,3-cis-dicarboxylic acid and dam = 2,2′-dipyridyl, 1,10-phenanthroline has been described. The complexes have been characterized by elementary analysis, infrared and electronic spectra and magnetic susceptibility measurements.The results of X-ray crystal structure analyses of [MnLdipy(H2O)3] · 2.5 H2O (1 a) and [CoLdipy(H2O)3] · 2,5 H2O (1 b) show, that both compounds crystallize isotypically and prove the octahedral coordination of the metal atoms. The dicarboxylate anion is coordinated to the central atom by an O atom of only one carboxylate group, the other one is in the ionic state. One O atom of each carboxylate group makes an intramolecular hydrogen bond with a water molecule of the coordination sphere. The other crystal water molecules form a network of H bonds one with another and with the complex molecules, thus stabilizing the crystal packing.
    Notes: Die Synthese von Koordinationsverbindungen der allgemeinen Zusammensetzung [MLdam(H2O)3] · 2,5 H2O mit M = Mn2+, Co2+, Ni2+; H2L = Bicyclo[2.2.1]hept-5-en-2-endo,3-cis-dicarbonsäure und dam = 2,2′-Dipyridyl, 1,10-Phenanthrolin wird beschrieben. Die Komplexe werden durch quantitative Analysen, IR- und Elektronenspektren sowie Magnetmessungen charakterisiert.Die Ergebnisse der Röntgenkristallstrukturanalyse von [MnLdipy(H2O)3] · 2,5 H2O (1 a) und [CoLdipy(H2O)3] · 2,5 H2O (1 b) zeigen, daß beide Verbindungen isotyp kristallisieren und belegen die oktaedrische Koordination der Metallatome. Das Dicarboxylat-Anion ist mit nur einem O-Atom am Zentralatom gebunden, die zweite Carboxylatgruppe liegt ionisch vor. Je ein O-Atom jeder Carboxylatgruppe geht eine intramolekulare Wasserstoffbrückenbindung mit einem koordinativ gebundenem Wassermolekül ein. Die restlichen Kristallwassermoleküle bilden ein die Packung stabilisierendes Wasserstoffbrückennetz untereinander und mit den Komplexmolekülen.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 859-864 
    ISSN: 0044-2313
    Keywords: 2,2-Bis(diisopropoxyphosphonyl)propyl methyltin dibromide ; synthesis ; crystal structure ; n.m.r. data ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Molecular Structure of 2,2-Bis(diisopropoxyphosphonyl)propyl Methyltin DibromideBy methylation of Me3SnCH2CH[P(O)(OPr-i)2]2 with NaH/MeI Me3SnCH2C(Me)[P(O)(OPr-i)2]2 (1) is obtained, which is converted by bromine into the dibromide MeBr2SnCH2C(Me)[P(O)(OPr-i)2]2 (2). An X-ray crystal structure analysis shows 2 to be monomeric. The tin atom is situated in the centre of a distorted octahedron, in which the functional substituent is intramolecular coordinated as tridentate ligand in a facial mode. The two organo groups are arranged in trans-position (C—Sn—C 155.1°), whereas the oxygen and bromine atoms are orientated cis to each other. The six-membered ring of the bicyclic molecular fragment of 2 which results from the coordination of the functional organo group to the tin atom shows a boat-conformation, whereas the two five-membered rings exist in twist-conformations. Multinuclear n.m.r. and i.r. data show that 2 retains its solid state structure also in nonpolar solvents.
    Notes: Durch Methylierung von Me3SnCH2CH[P(O)(OPr-i)2]2 mittels NaH/MeI erhält man Me3SnCH2C(Me)[P(O)(OPr-i)2]2 (1), das mit Brom in das Dibromid MeBr2SnCH2C(Me)[P(O)(OPr-i)2]2 (2) überführt wird. Nach der Röntgenkristallstrukturanalyse ist 2 im Festkörper monomer. Das Zinnatom befindet sich im Zentrum eines verzerrten Oktaeders, in dem der funktionelle Substituent intramolekular als tridentater Ligand in facialer Anordnung koordiniert ist. Die beiden Organoreste sind trans-ständig angeordnet (C—Sn—C 155,1°), während sich die Sauerstoff- und Bromatome in cis-Anordnung zueinander befinden. Der Sechsring des aus der Koordination des funktionellen Organorestes am Zinnatom resultierenden bicyclischen Molekülfragmentes von 2 weist Wannenkonformation auf, während die beiden Fünfringe in Twist-Konformationen vorliegen. Multikern-NMR- und IR-Daten belegen, daß 2 seine Festkörperstruktur auch in unpolaren Lösungsmitteln beibehält.
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