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  • Chemistry  (68)
  • Chemical Engineering  (3)
  • 1995-1999
  • 1990-1994  (68)
  • 1960-1964
  • 1945-1949
  • 1994  (68)
Collection
Keywords
Publisher
Years
  • 1995-1999
  • 1990-1994  (68)
  • 1960-1964
  • 1945-1949
Year
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and structure-property relations of polymers for light emitting diodes based on isolated chromophore units (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2023-2037 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New fluorescent polymers for electroluminescent devices were synthesized and characterized. In order to obtain polymers for blue light emitting diodes (LEDs), two different structural concepts based on isolation of the active chromophore units within the polymer main chain were investigated. In the first approach non-coplanar units were used to reduce the conjugation length in poly(arylenevinylene)s. In a second approach copolymers having isolated chromophore units in the polymers main chain were investigated. For this purpose, copolyesters containing isolated 1,2-dinaphthylethene chromophore units were synthesized and characterized. The influence of the chemical structure on the photo- and electroluminescence is discussed. On the example of copolyester 2b, which shows bluegreen electroluminescence (λmax = 497 nm) in a LED configuration, it was demonstrated that these polyesters can be used as light emitting layer in electrooptical devices.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950612
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  • 2
    Electronic Resource
    Electronic Resource
    Relative Reactivities of Acetals and Ethers under Friedel-Crafts Conditions (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 213-217 
    Details
    ISSN: 0009-2940
    Keywords: Alkylation ; Alkoxyalkylation ; Carboxonium ions ; Acetals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition experiments have been performed to determine the relative reactivities of acetals and ethers toward allyltrimethylsilane in the presence of catalytic amounts of BF3 OEt2. It is found that acetals R-CH(OMe)2 and their phenylogous p-anisyl ethers R-CH(p-MeOC6H4)(OMe) show very little differences in reactivity. The reactivity scales are employed to rationalize the results of Lewis acid-catalyzed additions of acetals and ethers to CC double bonds.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270130
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  • 3
    Electronic Resource
    Electronic Resource
    Relative Reactivities of Alkyl Chlorides under Friedel-Crafts Conditions (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 205-212 
    Details
    ISSN: 0009-2940
    Keywords: Alkylation ; Allylation ; Carbenium ions ; Friedel-Crafts reactions ; Linear free energy relationships ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Competition experiments have been performed to determine the relative reactivities of 23 alkyl chlorides toward allyltrimethylsilane in the presence of catalytic amounts of ZnCl2.The krel scale spans over 11 orders of magnitude from 1-adamantyl chloride (least reactive) to bis(p-methoxyphenyl)methyl chloride (most reactive compound). A fair correlation between the alkylating ability and the SN1 reactivity in solvolysis reactions is found, thus providing a quantitative basis for our long-standing working hypothesis that Lewis acid-catalyzed additions of alkyl halides to CC multiple bonds only yield 1:1 products if the reactants ionize faster than the products. Trityl chlorides do not follow this correlation and are 105 times less reactive than predicted from their SN1 reactivities.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270129
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  • 4
    Electronic Resource
    Electronic Resource
    Sulfur Compounds, 174. Preparation of Long-Chain Polysulfanes from Dialkoxysulfanes: Synthesis of Bis(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)tetrasulfane and -undecasulfane (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1219-1221 
    Details
    ISSN: 0009-2940
    Keywords: Tetrasulfane, bis(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)- ; Undecasulfane, bis(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)- ; Polysulfanes, bisorganyl ; Sulfanes, dialkoxy- ; 1-Thio-β-D-glucopyranose, tetra-O-acetyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dialkoxysulfanes (RO)2Sn (n ≥ 2) react with thiols R′SH as sulfur transfer reagents to form long-chain diorganylpoly-sulfanes R′2Sn+2 under mild conditions. Condensation of tetra-O-acetyl-1-thio-β-D-glucopyranose (acGlcSH) with diisopropoxydisulfane (iPrO)2S2 and diisopropoxynonasulfane (iPrO)2S9 at 40°C yields bis(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D-glucopyranosyl)tetrasulfane (1) (acGlc)2S4 and bis(2,3,4,6-tetra-O-acetyl-1-deoxy-β-D -glucopyranosyl)undecasulfane (2) (acGlc)2S11, respectively. The analogous reaction using diisopropoxymonosulfane does not yield the corresponding trisulfane.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270707
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemische und thermische Erzeugung von Thiocarbonylyliden aus 2,5-Dihydro-1,3,4-thiadiazolenIn vorläufiger Form von G. Mloston präsentiert auf dem 16. Internat. Symposium über die Organische Chemie des Schwefels, Merseburg, 10.-15. Juli 1994, Abstract Book, p. 2.46. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2527-2530 
    Details
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Photochemistry ; Flash pyrolysis ; Ylides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical and Thermal Generation of Thiocarbonyl Ylides from 2,5-Dihydro-1,3,4-thiadiazoles[*]Thermolysis of thiadiazolines 2a-c yields the corresponding thiiranes 5a-c exclusively. In contrast matrix photolysis in an organic glass at 77 K or in solid Ar at 10 K allows the detection of the thiocarbonyl ylides 3a-c, which are characterized by intense UV maxima at λ ≈ 350 nm. The thiocarbonyl ylides are formed in a stepwise manner and not directly from the thiadiazolines by a simple elimination of N2. In the first step a fragmentation into the thioketones 6a-c and diazomethane occurs, followed by the generation of methylene (8) from diazomethane (7). Addition of methylene to the thioketones 6a-c finally leads to the ylides 3a-c.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271226
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  • 6
    Electronic Resource
    Electronic Resource
    Heterogeneous suspension polymerization of vinyl chloride: Phase distribution and evolution (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 532-540 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A model for the phase distribution and evolution of the heterogeneous (suspension) polymerization of vinyl chloride is presented. Experimental information on pressure, temperature, and conversion has been obtained from a 34 liter bench reactor reproducing reaction conditions and product properties typical of industrial operation. A calculation procedure based on simple plant data is proposed for the description of the phase compositions and their evolution over the entire process. Results based on classical Flory-Huggins theory of solutions are presented and compared with existing data.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340612
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  • 7
    Electronic Resource
    Electronic Resource
    Literaturkarussell. Biologie (1994)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 28 (1994), S. III 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19940280513
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  • 8
    Electronic Resource
    Electronic Resource
    Products in methane combustion near surfaces (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1018-1025 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Emission of carbon monoxide (CO), formaldehyde (CH2O), and unburned methane (CH4) are calculated for premixed methane/air mixtures impinging on a flat surface as functions of surface temperature, equivalence ratio, and strain rate with detailed chemistry involving 46 reversible reactions and 16 species using numerical bifurcation theory. Multiple solutions with different selectivities to stable products are found. On the extinguished branch unburned CH4, molecular hydrogen (H2), CO, and CH2O dominate, whereas on the ignited branch carbon dioxide (CO2) predominates near the surface. Cold walls can promote the selectivity to CO and CH2O near extinction, and high flow rates can increase considerably the formation of CO, CH2O, and unburned CH4. For example, an ignited stoichiometric methane/air mixture (9.5% CH4 in air) impinging on a surface of 1,000 K is calculated to produce 2% CO, 150 ppm CH2O, and 3% unburned CH4 for a strain rate of 500 s-1. Maximum efficiency of CH4 and minimum selectivity to CH2O occur near the stoichiometric ratio, whereas minimum selectivity to CO occurs for fuel lean mixtures. Comparison of combustion near surfaces with freely propagating flames is also shown.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400612
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  • 9
    Electronic Resource
    Electronic Resource
    Ignition and extinction of flames near surfaces: Combustion of CH4 in air (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1005-1017 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ignition and extinction characteristics of homogeneous combustion of methane in air near inert surfaces are studied by numerical bifurcation theory for premixed methane/air gases impinging on planar surfaces with detailed chemistry involving 46 reversible reactions and 16 species. One-parameter bifuraction diagrams as functions of surface temperature and two-parameter bifurcation diagrams as functions of equivalence ratio and strain rate are constructed for both isothermal and adiabatic walls. Lean and rich composition limits for ignition and extinction, and energy production are determined from two parameter bifurcation diagrams. For a strain rate of 500 s-1, CH4/air mixtures exhibit hysteresis from ∼ 0.5% up to ∼ 12.5% and from ∼ 5.5% up to ∼ 13.5% near isothermal surfaces and adiabatic walls, respectively. Ignition temperature rises with composition from 1,700 to 1,950 K, without a maximum around the stoichiometric ratio. Under some conditions multiple ignitions and extinctions can occur with up to five multiple solutions, and wall quenching, kinetic limitations, and transport can strongly affect flame stability. Flames near the stoichiometric ratio cannot be extinguished by room temperature surfaces for sufficiently low strain rates. The role of intermediates in enhancing or retarding ignition and extinction is studied, and implications of the effect of catalytic surfaces on homogeneous ignition and extinction are discussed. Removal of H atoms and CH3 radicals by wall adsorption can increase extinction and ignition temperature of 6% CH4 in air by up to 300 K for a strain rate of 500 s-1.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400611
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  • 10
    Electronic Resource
    Electronic Resource
    Stereoselective pharmacokinetics of methadone in beagle dogs (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 492-495 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; methadone ; pharmacokinetics ; beagle dog ; iv administration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pharmacokinetics of methadone were studied in beagle dogs (n = 4) following intravenous administration of the racemate (0.5 mg/kg) and of the individual (R)-(0.25 mg/kg) and (S)-enantiomers (0.25 mg/kg) using a stereospecific HPLC assay. There was no significant difference between the pharmacokinetic parameters of (R)-methadone and (S)-methadone following administration of the individual enantiomers. Stereoselective differences were evident following administration of the racemate (P values for differences in AUC and CL were 0.001 and 0.046, respectively) and the clearance of the (S)-enantiomer was increased when administered as part of the racemate (316 ± 81 vs 487 ± 128 ml/min, P = 0.04). The data suggest that stereoselective disposition including potential enantiomer-enantiomer interactions should be considered in pharmacokinetic-pharmacodynamic studies of (R,S)-methadone. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060608
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