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  • 1990-1994  (7)
  • 1965-1969  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Editorial (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 4-4 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340102
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of ring cleavage of 1-Benzyl-4-phenyl-1,2,4-triazolium ChlorideDedicated to Prof. Dr. Dr. h. c. K. Schreiber on the occasion of his 65th birthday (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 231-236 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Benzyl-4-phenyl-1,2,4-triazolium chloride (1) is cleaved by aqueous sodium hydroxide to form 4-benzyl-1-formyl-1-phenyl-amidrazone (5), the structure of which is proved by mass spectroscopy. The kinetics of the cleavage reaction are studied by UV spectroscopy in methanol/water 1:1 (v/v) in the presence of Na2CO3/HCl buffer at pH values from 11.64 to 12.61. The reaction obeys a first-order kinetic law. The rate constants do not depend linearly on the hydroxide concentration. This is in coincidence with fast formation of the pseudobase from 1, followed by fast deprotonation to the pseudobase anion, and slow decay to the amidrazone. The pseudobase anion is proved spectroscopically, and its spectroscopically determined pKQOH = 12.7 coincides with that from the kinetic experiments. The equilibrium constant of pseudobase formation pKA = 10.99 is two orders of magnitude higher than that from the azocoupling of 1 [1] which shows that in the azocoupling not the pseudobase but its methyl ether (pKQOMe = 8.7) is active.4-Benzyl-1-formyl-1-phenyl-amidrazone (5) re-cyclizes in the presence of HCl in MeOH/H2O to form 1. The kinetics of this reaction are also studied.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340306
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  • 3
    Electronic Resource
    Electronic Resource
    An unsere verehrten Autoren und Leser des Journals für praktische Chemie (1969)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 1-2 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19693110102
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  • 4
    Electronic Resource
    Electronic Resource
    Relaissynthesen von Heterocyclen. IV. Darstellung von 4-Alkylamino-1,2,4-triazolen (1969)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 9-14 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die aus 4-Amino-1,2,4-triazol bzw. 3,5-Dimethyl-4-amino-1,2,4-triazol erhältlichen 1-Al-kyl-4-amino- bzw. 1-Alkyl-3,5-dimethyl-4-amino-triazolium-Salze gehen beim Erhitzen mit verdünnter Natronlauge durch Ringspaltung, Wanderung der gebildeten Acylgruppe und erneuten Ringschluß in die entsprechenden 4-Alkylamino-1,2,4-triazole über, deren Struktur bewiesen wird.Die Acylwanderung verläuft intermolekular, wie sich aus dem Kreuzungsexperiment ergibt.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19693110104
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  • 5
    Electronic Resource
    Electronic Resource
    Neue Derivate des Pyridazins (1969)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 286-295 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Das neuerdings leicht zugängliche 3-Amino-4-hydroxy-6-methy1-pyridazin 1 [1] erschließt einen neuen Zugang zu Derivaten des Pyridazins. Die Umsetzung mit salpetriger Säure liefert in verdünnter Schwefelsäure 3,4-Dihydroxy-6-methyl-pyridazin 3, in konz. Salzsäure dagegen 3-Chlor-4-hydroxy-6-methylpyridazin 2. Das Chloratom in 2 ist leicht nucleophil ersetzbar unter Bildung der 3-Hydroxy-, 3-Amino- bzw. 3-Phenylthio-Verbindungen 3, 7a-i. Noch leichter reagieren die entsprechenden 4-Methoxyverbindungen, so daß auch die interessanten3-Arylsulfonylamino-4-methoxy-Derivate 8k, l gut zugänglich sind.Mit Phosphoroxidchlorid liefert 2 das 3,4-Dichlor-6-methyl-pyridazin 10, das - ebenso wie 2 - in Gegenwart von Palladium reduktiv enthalogeniert werden kann, wobei 3-Methyl-pyridazin 11 bzw. das bisher unbekannte 4-Hydroxy-6-methyl-pyridazin 9 entstehen. Die Umsetzung des 3-Amino-4-hydroxy-6-methyl-pyridazins 1 mit Dimethylsulfat führt nur zum 4-Methoxy-Derivat 4. In gleicher Weise reagieren die 4-Hydroxy-6-methylpyridazine 7a-i und 2. Die Struktur der dargestellten Verbindungen wird gesichert. Die Verbindungen mit 4-Hydroxygruppe zeichnen sich durch hohe Schmelzpunkte, relativ geringe Löslichkeiten in Wasser und damit zusammenhängend sehr stark assoziierte IR-Banden der OH-Gruppe aus.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19693110214
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  • 6
    Electronic Resource
    Electronic Resource
    Relais-Synthesen von Heterocyclen. VII. Eine einfache Synthese von 3-substituierten 4-Amino-1,2,4-triazolen (1969)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 897-905 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch Alkylierung von 4-Acylamino-1,2,4-triazolen oder durch Acylierung von 1-Alkyl-4-amino-1,2,4-triazoliumsalzen entstehen 1-Alkyl-4-acylamino-1,2,4-triazoliumsalze 3. Diese gehen mit molaren Mengen wäßriger Alkalilauge in mesoionische Verbindungen 7 über, deren Struktur spektroskopisch und chemisch bewiesen wird. Mit überschüssiger wäßriger Lauge lagern sich 1-Alkyl-4-acylamino-1,2,4-triazoliumsalze 3 und ebenso die mesoionischen Verbindungen 7 in 3-Alkyl-4-alkylamino-1,2,4-triazole 14 um, sofern der Acylrest aliphatisch ist. Durch Dehydrierung und Verseifung werden daraus in zwei Fällen die entsprechenden 4-Amino-1,2,4-triazole gewonnen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19693110606
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  • 7
    Electronic Resource
    Electronic Resource
    Dediazoniation of 2,5-di(n-butoxy)-4-morpholino-benzenediazonium tetrafluoroborate sensitized by zinc phthalocyanine tetrasulfomorpholide (ZnPcTSM) in di-n-butyl phthalate (1993)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 335 (1993), S. 449-454 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dediazoniation of 2,5-di-(n-butoxy)-4-morpholino-benzenediazonium tetrafluoroborate (1) sensitized by zinc phthalocyanine tetrasulfomorpholid (ZnPcTSM) is studied in di-n-butylphthalate. The life-time of singlet-excited ZnPcTSM (τs = 3.0 ns) is not decreased by 1 whereas the static fluorescence at 689 nm is quenched. Thus, a ground-state complex is formed, Keq = 1730 M-1 showing an absorption band at 714 nm. A similar complex is formed with mono-n-butylphthalate being present if di-n-butylphthalate was not distilled in a good vacuum (1 torr), Keq = 1545 M-1. The decay of the triplet state in the presence of 1 is adequately treated as a reaction from the triplet-excited ground-state complex. Keq of the ZnPcTSM-diazonium salt complex is also obtained from quantum yields of the sensitized dediazoniation. A rather low intersystem crossing quantum yield of the complex amounting to 0.17 is deduced. ZnPcTSM is also bleached, but much weaker than expected for an oxidative electron transfer.The system works well - even under air - in dibutylphthalate micro droplets in gelatine coated on a PET-base.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19933350510
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  • 8
    Electronic Resource
    Electronic Resource
    A. Padwa (Hrsg.), organic photochemistry, Vol 11, 464 Seiten illustriert, Marcel Dekker, Inc., New York- Basel - Hong Kong 1991, gebunden, $ 189,75 (1992)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 334 (1992), S. 541-542 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19923340621
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  • 9
    Electronic Resource
    Electronic Resource
    Spectral Sensitization of Dediazoniation by the 2-electron-transfer system meso-tetraphenylporphinato-dichlorostannate(IV)/10-methyl-9-Phenyl-9.10-dihydro-acridine (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 241-250 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoreduction of meso-tetraphenylporphinatodichlorostannate(IV) (SnCl2TPP) by 9-phenyl-10-methyl-9,10-dihydro-acridine (ACH) in 1,2-dichloroethane/acetonitrile 1:1 (v/v) under argon proceeds only with a low quantum yield in spite of the fact that ACH is in other cases an excellent 2-electron donor. The reason may be the formation of a triplet exciplex which opens a new deactivation channel. Evidence for such an exciplex is given by means of the WARE treatment of flash-photolytic experiments and quantum yields of dediazoniation, Keq ≈ 650 M-1 and τexc = 46 μs.The exciplex reacts fast with p-N,N-dimethylamino-benzenediazonium tetrafluoroborate (kr = 4.1 × 108 M-1 s-1) under electron transfer leading to dediazoniation. At high ACH concentrations (8 × 10-3 M) the dediazoniation gives even at very low diazonium salt concentrations (≈ 4 × 10-5 M) quantum yields as high as 1.95 (0.37 stemming from sensitization by the SnCl2 complex of tetraphenylchlorine present as an impurity of SnCl2TPP. SnCl2TPP) remains unchanged during the sensitization reaction, i.e. the process is fully photocatalytic.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320216
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  • 10
    Electronic Resource
    Electronic Resource
    Photoreduction of Methyleneblue by the two-equivalent electron donor N-methyl-9-phenylacridane and the use of the system for the spectrally sensitized dediazoniation of p-N,N-dimethylamino benzenediazonium tetrafluoroborate (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 651-657 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoreduction of methyleneblue by N-methyl-9-phenylacridane (ACH) is studied in acetonitrile by means of flash photolysis and quantum yields. In the first step, due to fast proton shift within the original electron transfer product protonated semi-methyleneblue MBH.+ and the deprotonated donor radical (N-methyl-9-phenylacridanyl radical AC·) are formed with a rate constant of 2×108 M-1 s-1. In this radical pair a second electron is transferred very fast from AC· to MBH.+ with a rate constant ke2 ≈ 1010 s-1 to form leuco-methyleneblue and N-methyl-9-phenyl-acridinium salt (AC+). About 80% of the two-equivalent reduction product, leuco-methyleneblue, are formed within the first solvent cage during the flash. The maximum quantum yields of photoreduction approach ϕisc of MB+ as expected for a two-equivalent reduction reaction.The out-of-cage reaction consists of the known disproportionation of the protonated semi-methyleneblue MBH.+ and its reduction by the N-methyl-9-phenylacridanyl radical AC·. From the decay kinetics kred = 3×109 M-1 s-1 and kdis = 8×108 M-1 s-1 is derived.The system sensitizes the dediazoniation of p-N,N-dimethylamino benzenediazonium tetrafluoroborate efficiently even at very low diazonium salt concentrations (Φ = 0.6).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320510
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