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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 179-186 
    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: The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1515-1519 
    ISSN: 0947-3440
    Keywords: Macrocycles ; Recognition ; Piperazines ; Self-assembly ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New large, up to 45-membered macrocycles were synthesised from piperazine and m- and p-2,6-bis(bromomethyl)xylene under high dilution conditions. X-ray structures of compounds 3a, 4a, 5a, and 8b were determined. Surprisingly, none of the macrocycles prepared showed any inclusion properties towards small guest molecules. Instead, the compounds were found to self-organize during the packing process into larger structures due to the complementary of the molecular skeletons. In the crystalline state 3a forms nets, where the macrocycles are bound by H—C—H…N interactions to each other. 4a exits in a dimeric structure, which, in turn, further extends to a sheet structure. The positively charged phane 8b (di-dihydrochloride salt) adopts a chair-chair conformation, confirming that protonation of the N atoms does not change the conformation.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 16 (1993), S. 332-337 
    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: The effects of metal exchange between zeolites and alkali metals (Li, Na, K; zeolite Y, ZSM-5, T), alkaline earths (Mg, Ca, Sr, Ba; ZSM-5), transition metals (La, Ce, Cr, Mn, Fe, Co, Ni, Pd, Cu, Zn; ZSM-5) and aluminium (ZSM-5) on the conversion of ethanol were studied. Activities of the catalysts and selectivities for ethene, C3+ olefins, paraffins and arenes strongly depended on the cation, chosen for the modification. Only ethene was formed by alkali exchanged zeolites, the most active being Li-Y. This could be confirmed by a long-term ageing test with Li-Y pellets under semi-industrial conditions. The exchange of ZSM-5 with alkaline earths or transition metals permitted the formation of a wide variety of products, raning from high ethene to high aromatic yields. A correlation between certain product selectivities and electronegativity was only possible in a rough approximation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 706 (1967), S. 180-186 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Das Auftreten von Ellagsäure (7) und Brevifolin-carbonsäure (9) bei der Hydrolyse des Brevilagins 1 findet eine gute Erklärung durch die „Redox-Disproportionierung vicinaler Polycarbonylverbindungen“. Auch beim Erhitzen der Brevilagine mit Wasser oder Acetatpuffer werden diese Säuren nachgewiesen. Brevifolin-carbonsäure entsteht auch aus Terchebin beim Erhitzen mit Acetatpuffer. Bei der Behandlung des Terchebins und wahrscheinlich auch der Brevilagine mit Natronlauge entsteht neben der Brevifolin-carbonsäure auch Chebulsäure (15).  -  Diese experimentellen Befunde stützen die Hypothese, daß Brevifolin-carbonsäure und Chebulsäure in situ  -  auch in der Pflanze  -  aus Hexahydroxy-diphensäure entstehen können.
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 613-625 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,6-Anhydrofuranoses, XI1).  -  1,6-Anhydro-α-L-idofuranoseThe title compound 13 is prepared on different routes from suitable benzyl derivatives with gluco-configuration. Preparations use the susceptibility of axial 5-O-benzyl groups in this compounds to selective hydrogenolysis, thus allowing subsequent inversion of configuration in this position from D-gluco to L-ido by an oxidation/reduction sequence. Only 0.08% of 13 are found in the equilibrium mixture of idose in acidic medium. It is shown with 4-C-methyltalose as example, that the amount of 1,6-anhydrofuranoses in these equilibria rises significantly by changing the hydroxy groups in 4-position from secondary to tertiary ones.
    Notes: Die Titelverbindung 13 wird aus geeigneten benzylierten Derivaten mit gluco-Konfiguration auf verschiedenen Wegen synthetisiert. Bei der Darstellung wird die Möglichkeit der selektiven Hydrogenolyse von axialen Benzylgruppen in 5-Stellung in diesen Verbindungen genutzt, die eine anschließende Konfigurationsumkehr durch eine Oxidations-, Reduktionssequenz erlaubt und somit von der D-gluco- in die L-ido-Reihe führt. 13 ist in den sich in saurer Lösung der Idose einstellenden Gleichgewichtsgemischen lediglich zu 0.08% enthalten. Es wird anhand der 4-C-Methyltalose gezeigt, daß der 1,6-Anhydrofuranose-Anteil in diesen Gleichgewichten beim Wechsel der 4-Hydroxygruppe von einer sekundären zu einer tertiären erheblich steigt.
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 706 (1967), S. 169-179 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aus den Myrobalanen, den getrockneten Früchten von Terminalia chebula, wurde ein neuer, kristallisierter, gelber Gerbstoff isoliert, den wir „Terchebin“ nennen. Die Bruttoformel C41H30O26 unterscheidet sich von der Formel C41H32O27 der Chebulinsäure, die ebenfalls in den Myrobalanen vorkommt, nur um die Elemente einer Molekel Wasser.  -  Die Hydrolyse des mit o-Phenylendiamin umgesetzten Terchebins führte zur (bekannten) 1.3.6-Trigalloyl-β-glucose (3) und zum gleichen Phenazin 1, das auch aus den Brevilaginen entsteht. Der C14-Baustein, der im Terchebin (16) in 2- und 4-Stellung an die Trigalloyl-glucose gebunden ist, ist aber nicht die „Dehydro-hexahydroxy-diphensäure“ 4, wie in den Brevilaginen, sondern ein neuer Gerbstoffbaustein der Formel 7, den wir „Iso-hexahydroxy-diphensäure“ nennen. Bei der Reaktion mit o-Phenylendiamin zum Phenazin wird die Säure 7 unter Wasserstoffverlust aromatisiert.  -  Aus dem mit Phenylendiamin umgesetzten und anschließend methylierten Terchebin wird bei der Hydrolyse die optisch aktive Tetramethoxy-phenazin-dicarbonsäure 14 isoliert, deren Dimethylester 15 positiv dreht und das Spiegelbild der aus Brevilagin 1 gewonnenen, linksdrehenden Form darstellt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 706 (1967), S. 187-197 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aus dem Extrakt der Myrobalanen wurden die 1.3.6-Trigalloyl-β-glucose und die 1.2.3.4.6-Pentagalloyl-β-glucose isoliert. Die beiden Verbindungen waren zwar als Abbauprodukte von anderen Gerbstoffen bekannt, aber nicht selbst in der Natur gefunden worden. Aus ihrer Menge wurde geschlossen, daß damit über 2/3 der Myrobalanengerbstoffe aufgeklärt sind. Die 1.3.6-Trigalloyl-glucose ist kein Abbauprodukt der Pentagalloyl-glucose, sondern ein selbständiger Gerbstoff. Die beiden neu in den Myrobalanen aufgefundenen Oligogalloyl-glucosen können als Schlüsselsubstanzen für die Entstehung der Chebulinsäure (1), Chebulagsäure (2), des Terchebins (4) und des Corilagins (6) aufgefaßt werden.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,6-Anhydrofuranoses, X. A Simple Synthesis for 1,6-Anhydro-3-deoxy-α-D-xylo-hexofuranoseTreatment of 1,6-anhydro-2,3,5-tri-O-tosyl-α-D-galactofuranose (1) with KOH in dioxane/water gives by way of cis-elimination 1,6-anhydro-3deoxy-5-O-tosyl-α-D-threo-hexofuranos-2-ulose (2) in good yield, which tends to dimerize easily in an aldol type reaction to 3. NaBH4 reduces 2 stereoselectively to 4a Removal of the tosyl group giving the title compound 4c is accomplished by sodium amalgam.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: [2.2]Metacyclophanes ; Chromium complexes ; Chirality (helicity, planar chirality) ; Clathrates ; Configuration, absolute ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regioselective Complexation of [2.2]Metacyclophanes with TriamminetricarbonylchromiumThe new [2.2]phanes 12, 13, 15, and 17 have been prepared. For the preparation of the known phane 16 a new route has been developed which leads to better yields and includes an interesting reduction with Raney nickel of the naphthalene ring of 15 to a tetrahydronaphthalene ring (→17). The phanes react regioselectively with triamminetricarbonylchromium, which results exclusively in the complexation of the sterically less hindered benzene ring. The bis(tricarbonylchromium) complexes of 18 and 17 were available in good yields, when two equivalents of the precursor of the tricarbonylchromium group were used. 18a was lithiated at -78°C, and the lithiated complexes were trapped with either chlorotrimethylsilane or ethyl chloroformate to yield 4- and 5-substituted products in a ratio of 4:5. Ten X-ray structures, including those of six transition metal π complexes, which were investigated and compared under the aspect of steric interactions between the tricarbonylchromium group and the substituent at the arene ring, are discussed. Interestingly, the tricarbonylchromium group shows no noticable effect on the boat-like deformation of the benzene ring in [2.2]metacyclophanes. A new definition of the “angles of helicity” in helical [2.2]phanes is introduced.
    Additional Material: 6 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0009-2940
    Keywords: Chirality ; Chromium complexes ; Helicity ; Configuration (absolute) ; [2.2]Metacyclophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tricarbonylchromium Complexes of Chiral [2.2]Metacyclophanes: Syntheses, Structures, and Chiroptical PropertiesHPLC-baseline separations of three racemic cyclophanes 3, 4, and 6 on cellulose tris(3,5-dimethylphenyl)carbamate led to their enantiomers with high optical purity. Complexation of (-)-3 and (+)-3 with triamminetricarbonylchromium yielded chiral Cr(CO)3 complexes (-)-(S)P-(3S)M-3a and (+)-(R)P-(3R)M-3a stereoselectively. Derivatisation of the complexes by lithiation and reaction with electrophiles gave new substituted chiral Cr(CO)3 complexes of [2.2]metacyclophanes regio-selectively. X-ray structure analyses of one chiral chromium complex (-)-(R)P-(5S)M-14a and three chiral chromium-free ligands (-)-(S)P-3, (-)-(S)P-4, and (-)-(S)P-6 led to the assignment of the absolute configurations of all chiral compounds discussed here. The influences of substituents on the chiroptical properties are investigated. The helicity of [2.2]metacyclophanes is discussed. For the first time X-ray structure analyses were performed of a bis-Cr(CO)3 complex (9a) as well as of the first chromium complex 10a of a heteraphane. Dethioketalisation of (-)-(S)P-3 with NBS gave (-)-(S)P-18, the absolute chirality of which has been known, under retention of configuration.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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