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  • Chemistry  (47)
  • Analytical Chemistry and Spectroscopy
  • Wiley-Blackwell  (47)
  • 1995-1999
  • 1990-1994  (47)
  • 1994  (47)
  • 1
    Electronic Resource
    Electronic Resource
    Wanzlick-Carbene in der [4 + 1]-Cycloaddition mit Bis(methylthio)- und Bis(trifluormethyl)-1,2,4,5-tetrazin (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1803-1806 
    Details
    ISSN: 0009-2940
    Keywords: Singlet carbenes ; [4 + 1] Cycloadditions ; 1,2,4,5-Tetrazines ; SEAr reactions, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Wanzlick Carbenes in the [4 + 1] Cycloaddition Reaction with Bis(methylthio)- and Bis(trifluoromethyl)-1,2,4,5-tetrazineThe 3,6-disubstituted 1,2,4,5-tetrazines 3 and 4 have been submitted to a [4 + 1] cycloaddition reaction with the nucleophilic singlet carbenes (Wanzlick carbenes) 2a-d, which are generated from the precursors 1a-d. With 3 as diazadiene the expected spiro compounds 6a-d are formed. In contrast to this presumed two-step reaction sequence of 3, with the tetrazine 4 the cascade cycloaddition/cycloelimination is surprisingly followed by an intramolecular electrophilic aromatic substitution to yield the chiral tetracyclic compounds of type 8 with high diastereoselectivity. The crystal structure of 8d has been determined by X-ray diffraction methods.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270933
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  • 2
    Electronic Resource
    Electronic Resource
    Face-Selective and endo-Selective Cycloadditions with Enantiomerically Pure Cyclopentadienes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2505-2509 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopentadienes, bicyclic ; Face selectivity ; endo selectivity ; Chiral discrimination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general synthetic route to the enantiopure bicyclic cyclopentadienes (S)-3 and (R)-3 of the hydrindane series, starting from the Hajos-Wiechert ketone 4 or its enantiomer is described. Reasons for the excellent face and endo selectivity of cycloadditions and the resulting consequences for chiral recognition are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271223
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  • 3
    Electronic Resource
    Electronic Resource
    Reaktion von Decaboran mit dem Phosphaalkin PCtBu (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 93-95 
    Details
    ISSN: 0009-2940
    Keywords: Decaborane ; 1-Phosphabutin, 3,3-dimethyl ; Bis(decaboranyl)methane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Decaborane with the Phosphaalkyne PC tBuThe borane B10H12(SMe2)2 (1) reacts with the phosphaalkyne P°CtBu to form the product [B10H11(SMe2)][C(tBu)-PH](B10H12) (2), in which two B10 units are linked by a HP-CtBu bridge. The B10 unit B is simply bound to the bridge C atom, whereas the B10 unit A is bound to both bridging atoms, P and C, by atom B6 and, moreover, to the P atom by atom B5. The solvate complex 2 · CH2Cl2 crystallizes in the space group P¯.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270115
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Thermolyse von Amin - arachno-Nonaboran (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 853-855 
    Details
    ISSN: 0009-2940
    Keywords: Diethylamine - arachno-nonaborane ; Diethylamine - octadecaborane ; conjuncto-Bis[6′5′:5,6]decaborane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Thermolysis of Amine-arachno-NonaboraneTwo molecules of diethylamine-arachno-nonaborane, B9H13-(NHEt2), undergo a condensation at 140°C to give diethylamine-conjuncto-bis[6′,5′:5,6]decaborane, B18H20(NHEt2) (4). The deprotonation of 4 yields the anion [B18H19(NHEt2)]-which can be crystallized with the cation [NEt3(CH2Ph)]+ (space group P1).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270512
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  • 5
    Electronic Resource
    Electronic Resource
    (Z)-1,1-dichloro-2-(4-benzyloxyphenyl)-2,3-bis(4-methoxyphenyl)cyclopropane: The synthesis and enantiomeric separation of an antitumor agent (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 41-45 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; Chiralpak AD ; amylose carbamate stationary phase ; antiestrogen ; breast cancer ; dichlorotriarylcyclopropane ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Z)-1,1-Dichloro-2-(4-benzyloxyphenyl)-2,3-bis(4-methoxyphenyl)cyclopropane (5), a potential antitumor agent designed to treat breast cancer, was prepared in three steps. A stereospecific palladium-catalyzed cross coupling reaction which provided the intermediate (Z)-triaryl alkene 4 was a crucial step in the synthesis. Makosza phase transfer reaction on 4 gave the enantiomeric (Z)-dichlorocyclopropane derivatives 5 which were resolved by semipreparative HPLC on a chiral stationary phase consisting of amylose tris-3,5-dimethylphenyl carbamate coated on silica gel. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060108
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  • 6
    Electronic Resource
    Electronic Resource
    Modelling of coadsorption of different-sized molecules by using methods of statistical thermodynamicsDedicated to Professor Dr. Dr. h.c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 119-126 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using methods of statistical thermodynamics, adsorption isotherms for the description of multicomponent chemisorption of different-sized molecular species are derived by assuming the adsorbing surface to be energetically homogeneous and by neglecting lateral interactions between the adsorbed particles. In the first part of this contribution, the adsorption equilibria for a mixture of different-sized chain molecules adsorbed on a lattice of coordination number z are discussed supposing each unit of a given chain to bind to one adsorption site only. In the second part, the coadsorption of molecular species consisting of a different number of segments on a continuous surface is treated. A comparison of the predicted to the measured isotherms for the coadsorption of two freon species on activated carbon shows that the proposed equations describe the results of the coadsorption measurements sufficiently well, provided the adsorption data for the pure components have been determined experimentally.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170209
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  • 7
    Electronic Resource
    Electronic Resource
    On the polymerization of N,N,N′,N′-tetramethyl-α,ω-alkanediamines with dibromoalkanes - an in-situ NMR study (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1777-1795 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Based on the Menschutkin reaction, α,ω-alkanediamines with α,ω-dibromoalkanes were employed to synthesize cationic polyelectrolytes named ionenes. By means of in-situ 13C NMR we have characterized the influence of ionic charges on the reactivity of the polymerizing species. The progress of aliphatic ionene polymerization has been found to be a complex reaction. At least four elementary building reactions and two side reactions (Hoffmann degradation and intramolecular cyclization) have been detected in the course of ionene polymerization. As a result, the broad molecular weight distribution which is usually found in ionenes can be explained in terms of the kinetics and by side reactions. Also, the difficulty of achieving high molecular weight ionenes can be understood on the basis of our NMR results.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950527
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  • 8
    Electronic Resource
    Electronic Resource
    Thermotropic elastomers with poly(oxy-1,4-butanediyl) units in the main chain (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2633-2651 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The paper describes the synthesis of thermotropic elastomers from trimellitimide-terminated poly(oxy-1,4-butanediyl) [synonyms: poly(tetramethylene ether glycol), PTMG; poly(tetrahydrofuran), poly(THF)] and acetoxy group-terminated rigid blocks. Copolyester imides are formed by transesterification polycondensation in the melt. According to 13C NMR investigations, their chain sequence distribution is characterized by a block-like structure in which the preformed rigid units are partially exchanged by transesterification reactions during the melt polycondensation. The degree of transesterification depends on the reaction time. The influence of the length of the flexible PTMG units and of the concentration of rigid units on the phase behaviour as well as on the thermal behaviour and the dynamic-mechanical behaviour of the block copolymers is discussed with respect to aromatic model compounds.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950731
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  • 9
    Electronic Resource
    Electronic Resource
    Electrical and optical properties of the transition metal iron in ZnTe and CdTe (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 223-232 
    Details
    ISSN: 1057-9257
    Keywords: CdTe ; ZnTe ; Impurities ; Spin resonance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We present results of electron paramagnetic resonance (EPR) and optical spectroscopy on different charge states of the transition metal impurity iron in ZnTe and CdTe. We identify the energy level position of the Fe+ acceptor in ZnTe at Ev + 1.7eV and estimate its position in CdTe. Ionisation transitions from Fe+to the conduction and valence bands ar found in both absorption spectroscopy and photo-EPR. Optical intra-defect tracsitions from Fe+ to crystalfield-split excited states ar resolved for the first time. This assignment to Fe2+ is based on optically detected EPR. Application of both far-infrared Fourier transform and EPR spectroscopy allows the determination of the total iron concentration in all charge states.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860030132
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  • 10
    Electronic Resource
    Electronic Resource
    38. Beispiele zur Modellierung nicht trivialer Phasengleichgewichte bei der Verfahrenssimulation (1994)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 66 (1994), S. 1186-1186 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330660939
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