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  • 1980-1984  (11)
  • 1975-1979  (12)
  • 1965-1969  (4)
  • Chemistry  (27)
  • Nuclear Reactions
  • Recombinant DNA
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal cyclization of the pyrimidine-N-oxide dicarbamate 2 gives a 95:5 mixture of the 2-oxo-2H-[1,2,4]oxadiazolo[2,3-a]- and [2,3-c]pyrimidinecarbamates 3 and 4. An efficient procedure for the conversion of 3 to 4, and vice versa, is described.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1445-1453 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of new 2-oxo-2,8-dihydro-[l,2,4]-oxadiazoo-[2,3-a] pyrimidine-carbamates 3 described in this paper is based upon a regioselective heterocyclization of the pyrimidine-2,6-bis (alkoxycarbonylamino) N-oxides 4. Structural and mechanistic aspects of that cyclizalion are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dye-sensitized photooxygenation (1O2-reaction) of the symmetrically 3,3-dialkyl-substituted allyl alcohols 1-6 (A, Table 1) and the E- and Z-isomers of the 3-methyl-3-alkylsubstituted allyl alcohols 7-11 (A1, Table 2) has been studied. The α, β-epoxyaldehydes B and B1 and the β-hydroperoxy-homoallyl alcohols C, C1 and D1 were practically the sole oxygenation products formed. The rate and selectivity of the 1O2 additions were found to be markedly dependent on the degree of substitution (i.e. H-availability) at the allyl position which is Z-orientated to the carbinol group. The allyl alcohols with a Z-3-methyl group, 1 and the E-isomers of 7 to 10, showed practically the same reactivity towards 1O2 and formed only the two oxygenation products of type B1 and C1 (ratio close to 60:40). In contrast, the allyl alcohols with a Z-3-methylene group, 2 and the Z-isomers of 7 to 9, reacted more slowly with 1O2 and yielded all the three possible products B1, C1 and D1 in a very different ratio of ∼ 80:10:10. However, from both the E- and Z-isomers of the alcohols 7 to 10 the formations of the two oxygenation products were always strongly favoured (85-100%) which result from 1O2 additions at the disubstituted side of the double bond. This behaviour is thus completely analogous to that of the corresponding trisubstituted olefins previously studied [1]The same side-specific selectivity in 1O2 ene additions to several E/Z-isomeric and deuterium-labelled olefins has also been described recently by C.M. Stephenson et al. [2] (we thank Dr. V. Rautenstrauch and Prof. C.W. Jefford for informing us about this work). The similar behaviour of enol ethers, which react with 1O2 preferentially at the RO-substituted side, had been observed earlier by C.S. Foote et al. [3] and extended to numerous derivatives by J.M. Conia et al. [4] [5]. and follows a new selection rule, termed syn-preference [1], in the ene addition of 1O2.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of new 2-oxo-2,8-dihydro-[l,2,4]oxadiazolo-[2,3-a]pyrimidine-carbamates 1 was established by correlating the IR. and NMR. data with these of analogous compounds. A X-ray crystallographic analysis of 1c gave an unequivocal proof of structural assignment.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipophilic Tetraazamacrocycles: Application to Liquid-liquid Extraction of Metal IonsLiquid-liquid extraction of Co2+, N2+, Cu2+, Zn2+, Cd2+, Pb2+, and Ag+ by lipophilic tetraazamacrocycles is reported in different solvents. Extraction efficiency is sensitive to the metal ion identity, the cavity size of the macrocycle and the pH of the aqueous phase. The influence of the organic receiving phase and the anion identity is discussed and expressed in terms of donnor-acceptor concepts. Further-more, the lipophilic tetraazamacrocycles exhibit high extraction efficiency towards these transition- and heavy-metal ions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to 2-amino-6-(methoxycarbonyl)amino-4-(1,2,3,6-tetrahydro-1-pyridyl)pyrimidine 1-oxide (3) is described. Methyl [1-ethoxy-2-(ethoxycarbonyl)-ethylidene]carbamate (5) reacted with guanidine to the pyrimidinecarbamate 6, which was successively transformed into methyl 2-amino-6-(p-tolyslulfonyl)oxy-4-pyrimidinecarbamate (8). Oxidation of 8 led to the corresponding pyrimidine N-oxide 9, a useful starting material to 3.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipophilic Tetraazamacrocyles: Extraction of Metal Ions by Impregnated ResinExtraction of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ and Ag+ by lipophilic tetraazamacrocycles dispersed on a solid matrix (Amberlite XAD7) is reported. Extraction efficiency is sensitive to the metal ion identity and the cavity size of the macrocycle. The influence of kinetic factors upon extraction efficiency is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1285-1294 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: High quality packaging films from hydroxyethyl cellulose of low degree of substitution (DS) are being produced commercially in this country and abroad. Increasing demand for this and a variety of other applications requires a rapid and simple production control method for determining hydroxyethyl substitution of cellulose. None of the known analytical methods fulfills these requirements. The present paper describes a method which is based on the relationship between the solubility and the molar hydroxyethyl substitution of hydroxyethyl cellulose. A washed and dried sample of hydroxyethyl cellulose is dissolved in 7% aqueous sodium hydroxide. Methyl alcohol, a nonsolvent, is used to precipitate a fraction of the sample. The turbidity of the equilibrium system is determined and optical density readings are related to molar substitution. The method is most useful in low DS ranges of 2-8% EtO but is susceptile to broader application through adjustment of the composition of the solvent-nonsolvent mixture. Relatively large variations in DP can be tolerated. The molar substitution level of an hydroxyethyl cellulose sample can be obtained in 40 min. by this method, making it a practical production control technique.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 1079-1085 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Cotton and cotton/polyester blends treated with phosphorus-nitrogen polymers and poly-(vinyl bromide) for flame retardance were examined in the electron microscope. A considerable amount of the poly(vinyl bromide) was retained by the cotton fibers. Expansion studies indicated that the poly(vinyl bromide) acted either as a morphologic adhesive or as a nonpolar matrix impervious to penetration by methacrylate before swelling.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 12 (1968), S. 487-507 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Technology is now available to produce superior quality rayon fibers with a wide range of tenacity, elongation, and modulus. In-process modification results in rayon fibers suitable for a great variety of end uses as continuous filament yarn or staple, either in 100% construction or blended with synthetics. In addition to versatility, such modified rayons have unique dimensional stability and chemical resistance. The developments leading to a method for preparation and the characteristics of such a highly oriented rayon, modified through trace crosslinking, are described here. The discovery of a triple modifier system utilizing poly(ethylene glycol)-dimethylamine in the viscose and small amounts of formaldehyde in a low zinc sulfate-containing acid spin bath, has made possible the production of rayon fibers with high strength (ca. 6 g./den.) and adequate elongation (ca. 10%) for good processability and which are highly resistant to caustic soda. Among the variables studied were spin bath composition, especially the relationship between formaldehyde and zinc sulfate concentration, and bath temperature. Optimum modifier concentrations are defined with regard to particular fiber properties desired. The effects on orientation and fiber physical properties of spinning modified viscose into formaldehyde-free and formaldehyde-containing spinning systems are described. High orientation coupled with trace crosslinking provides greatly improved resistance to caustic soda over that resulting from orientation alone.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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