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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 169 (1979), S. 111-113 
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Beim thermischen Abbau von Chitin, das auch Bestandteil einiger Nahrungsmittel ist, wird als flüchtige organische Hauptkomponente Acetamid gefunden (9% des Trockengewichtes), was möglicherweise von physiologischer Bedeutung ist. Thermoanalysen zeigen, daß die Zersetzung bereits bei 200 °C beginnt.
    Notes: Summary Thermal degradation of chitin, which is a constituent of some foods, yields as main volatile compound acetamide (9% of dry weight), a fact with possible physiological implications. Thermal analysis shows decomposition beginning at 200 °C.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 63-69 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal dimerization of methyl acrylate to dimethyl 2-methyleneglutarate was performed in a high pressure-high temperature flow apparatus at temperatures up to 420°C and pressures up to 200 bar. The head to head dimer dimethyl 2-methyl-3-methylenesuccinate was observed, too. Methyl vinyl ketone and acrylonitrile are able to dimerize analogously.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 749-762 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biological materials, rich in hemicelluloses (birch and pine wood, wheat straw and rice hulls) were disintegrated batchwise in a flow reactor with pure water at elevated temperatures and pressures. The resulting extractives and residual fibre compounds were characterized. Because of rapid removal of carbohydrate based extractives from the hot reaction zone, the degradation of pentosans and hexosans to furfural and hydroxymethylfurfural could be limited to only a small amount. Contrary to normal prehydrolysis conditions employing a sealed batch reactor, temperatures of 190 to 210°C and residence times of goods of 60 min are the optimum. Thus, hemicelluloses are dissolved and isolated with up to more than 90% yield. At temperatures above 225°C severe destruction of hemicelluloses and solvolysis of cellulose starts. Depending on disintegration temperatures, pentosan average molecular weights (M̄w) vary in case of birch wood between 3800 at 150°C and 900 at 225°C. The content of monomers rises with temperature and reaches a maximum of 45% at 225°C. DPw of residual cellulose is also temperature dependent and varies in case of birch wood and wheat straw between 1500 and 450. Lignin, which is mostly not dissolved, can be removed almost quantitatively by further treatment of the residue with ethanol/water at 250°C, thus allowing the isolation of relatively pure cellulose.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    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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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1063-1067 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Unsaturated Carbohydrates by Ester Pyrolysis, IV1).  -  Thermal cis Eliminations from Completely Acetylated Aldo- and KetofuranosesThermal cis elimination of the anomeric acetyl group in completely acetylated furanoses does not yield the expected hydroxyglycals but gives by further elimination of another molecule of acetic acid substituted furans. Thus, β-D-ribofuranose tetraacetate 1 and β-D-galactofuranose pentaacetate 3 give the furans 2 or 4, respectively. α-D-Fructofuranose pentaacetate 5 equally yields the furan derivative 6. But in this case the E and Z isomers 7 and 8 with exocyclic double bond are also formed. Further rearrangement of these products is not observed.
    Notes: Die thermische cis-Eliminierung der anomeren Acetylgruppe in vollständig acetylierten Furanosen bleibt nicht auf der Stufe des Hydroxyglycals stehen, sondern führt unter Eliminierung eines weiteren Moleküls Essigsäure zu substituierten Furanen. So liefern β-D-Ribofuranosetetraacetat 1 und β-D-Galactofuranosepentaacetat 3 die Furane 2 bzw. 4. Auch α-D-Fructofuranosepentaacetat 5 ergibt den Furanabkömmling 6. Daneben werden jedoch die E- und Z-Isomeren 7 und 8 mit exocyclischer Doppelbindung gebildet. Weitere Umlagerung dieser Produkte wird nicht beobachtet.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 1052-1062 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Unsaturated Carbohydrates by Ester Pyrolysis, III1).  -  Thermal cis Eliminations from Completely Acetylated KetopyranosesThe pentaacetates 1 and 6 derived from α-L-sorbopyranose and β-D-fructopyranose dissolved in acetone regioselectively eliminate at temperatures of 230-270°C in a flow apparatus within 0.5-1 min the 2-O-acetyl group as acetic acid. Primarily the Z isomers 2 and 7 with exocyclic double bond (1,3,4,5-tetra-O-acetyl-2,6-anhydro-hex-1-enitols) are formed. At higher temperatures the thermodynamically more stable E isomers 3 and 8 are also found. 1H NMR spectra show an equilibrium of alternative chair conformations 2C5 and 5C2 in 2 and 7, but E isomers 3 and 8 exclusively adopt 5C2 conformations with three or in case of 7 two axial substituents. From these compounds the tetraacetyl-2,6-anhydro-3-deoxy-al-hex-2-enoses 4 and 9 are formed by a [3,3] sigmatropic rearrangement (allyl shift). Their conformation is dominated by the allylic effect. Catalytic hydrogenation of 4 or 9 yields 2,6-anhydro-3-deoxy-al-hexoses 11 and 12 or 13. Unsatured sugars 2 and 3 are reduced to give the 1,5-anhydro-D-sorbitol derivative 14.
    Notes: Die in Aceton gelösten Pentaacetate 1 und 6 der α-L-Sorbopyranose und der β-D-Fructopyranose eliminieren im Temperaturbereich 230-280°C bei Verweilzeiten von 0.5-1 min in einer Strömungsapparatur regioselektiv die 2-O-Acetylgruppe als Essigsäure. Hierbei werden primär die Z-Isomeren 2 und 7 mit exocyclischer Doppelbindung gebildet (1,3,4,5-Tetra-O-acetyl-2,6-anhydro-hex-1-enite). Bei höheren Temperaturen werden auch die thermodynamisch stabileren E-Isomeren 3 und 8 gefunden. Aus den 1H-NMR-Spektren ergibt sich, daß bei 2 und 7 ein Gleichgewicht der alternativen Sesselkonformationen 2C5 und 5C2 vorliegt, hingegen die E-Isomeren 3 und 8 ausschließlich 5C2-Konformationen mit drei bzw. zwei axialen Substituenten einnehmen. Als Produkt einer nachfolgenden [3,3]-sigmatropen Umlagerung (Allylverschiebung) werden weiterhin die Tetraacetyl-2,6-anhydro-3-desoxy-al-hex-2-enosen 4 und 9 beobachtet. Ihre Konformation wird durch den „Allyl-Effekt“ bestimmt. Die katalytische Hydrierung von 4 bzw. 9 führt zu den 2,6-Anhydro-3-desoxy-al-hexosen 11 und 12 bzw. 13. Entsprechende Reaktion der ungesättigten Zucker 2 und 3 liefert das 1,5-Anhydro-D-sorbit-Derivat 14.
    Additional Material: 3 Tab.
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