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  • 1
    Electronic Resource
    Electronic Resource
    1H-, 13C- und 15N-NMR-Untersuchungen zur Tautomerie von Bispyrazolonen vom Typ der 4,4′-Methyliden-bis-(3-stearoylamino-1-phenyl-pyrazolin-5-one) (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 371-382 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H-N.M.R., 13C-N.M.R., and 15N-N.M.R.-Investigations Concerning Tautomerism of Bispyrazolons of 4,4′-Methyliden-bis-(3-stearoylamino-1-phenyl-pyrazolin-5-on) TypeWith the help of 1H, 13C and 15N chemical shifts of the n.m.r. signals of the structure elements OH, NHCO, 13C-5, 15N-1, 15N-2 and 15N-2-H and using the coupling constants nJ(15N—H) and nJ(13C—15N) (n = 1, 2) of the doubly 15N labelled bispyrazolone 1, a chelated and an associated species were shown to exist in the slightly polar solvent CDCl3. The chelated bispyrazolone (BC)ch contains one pyrazolone ring in the tautomeric NH form B and the other in the tautomeric OH form C. In the associated bispyrazolone (BB)as, both pyrazolone rings exist in the NH form B. Observation of the time, concentration and temperature dependence of the n.m.r. spectra of 1 resulted in the detection of complex exchange processes in tautomeric equilibrium. Apart from the intermolecular exchange process (BC)ch ⇌ (BB)as, another exchange process (BC)ch ⇌ (CB)ch occurs, with intermolecular interactions being involved. It has been established that in the case of substitution in the methylidene bridge (2, 3) the lefthand side of the equilibrium (BC)ch ⇌ (BB)as participates in the process to a greater extent than in the case of 1 (unsubstituted methylidene bridge).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270304
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  • 2
    Electronic Resource
    Electronic Resource
    Untersuchungen zum photochemischen Ausbleichverhalten von tautomeriefähigen Azofarbstoffen. VIV. Mitt.: R. Haessner, H. Mustroph, J. Epperlein, J. prakt. Chem. 325 (1983) 943.. Zur photochemischen Oxydation von Phenylazo-acetylacetonen und Phenylazopyrazolonen durch SingulettsauerstoffHerrn Doz. Dr. K. Schiller zum 60. Geburtstag gewidmet (1984)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 326 (1984), S. 979-984 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigations of the Photo-Fading of Tautomeric Azo Dyes. VI. The Photochemical Oxidation by Singlet Oxygen of Phenylazoacetylacetones and PhenylazopyrazolonesThe dye-sensitized photo-oxidation by singlet oxygen of phenylazoacetylacetones (1) and Phenylazopyrazolones (2) has been investigated. The photo-fading of dyes is accelerated in the presence of Methylene Blue, a sensitizer of singlet oxygen, in airsatured methanolAn excellent relationship exists between the fading-rate of a series of dyes (1) and Hammett-σ-constants. An unexpected trend was found for photo-fading of a series of dyes (2). The Hammett plot consists of two parts, with a negative slope derived from electron-releasing substituents and a positive slope derived from electron-withdrawing substituents. The anomalous photo-fading is due to an attack of singlet oxygen on the more reactive anion of the phenylazopyrazolones in the case of electron-withdrawing substituents. In methanol containing acetic acid the dyes (2) exist only as the hydrazone tautomers. Under these conditions the fading-rate show a linear relationship with σ-constants.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19843260617
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  • 3
    Electronic Resource
    Electronic Resource
    NMR-spektroskopische Untersuchung von 2,4-Bis(3,5-di-tert.-butyl-4-hydroxyphenyl)-2,4-dithioxo-1,3,2λ5,4λ5-dithiadiphosphetan und ausgewählten AlkoholyseproduktenHerrn Professor Dr. Hans-Albert Lehmann zum 70. Geburtstag gewidmet (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 361-364 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N.M.R. Investigation of 2,4-Bis(3,5-di-tert.-butyl-4-hydroxyphenyl)-2,4-dithioxo-1,3,2λ5,4λ5-dithiadiphosphetane and Selected Alcoholysis Products
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310224
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Zur Umkupplung von 4-Arylazo-2-pyrazolin-5-onen mit p-Chinondiiminkationen (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 275-283 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recoupling of 4-Arylazo-2-pyrazoline-5-ones with p-Quinonediimine Cations4-Arylazo-2-pyrazoline-5-ones (1a-j) readily undergo coupling reaction with p-quinonediimine cations (2a, b) to form azomethin dyes (3a, b). The dependence of the rate constants kK of the dye formation on the substituents of 1a-j as well as on the ionic strength show that the rate-determining step of the coupling reaction is the formation of the intermediate 4 in a bimolecular reaction between the carbanions of 1a-j and p-quinonediimine (2a, b).It became evident that the benzenediazoniumion (5a-j) is eliminated in the reaction of 4 to 3a, b. Under the coupling conditions used, substituted benzene is formed in the reduction reaction of 5a, b by the p-phenylendiamine (7a, b) or by the leuco dye (6a, b).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280217
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  • 6
    Electronic Resource
    Electronic Resource
    Phosphororganische Antioxidantien. IV. Chemisch induzierte Polarisation von 31P-Kernen in der Reaktion cyclischer Phosphite mit HydroperoxidenHerrn Prof. Dr. R. Mayer zum 60. Geburtstag gewidmet (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 763-771 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organophosphorus Antioxidants. IV. Chemical Induced Polarization of 31P Nuclei in the Reaction of Cyclic Phosphites with Hydroperoxides31P-n.m.r. CIDNP is observed in the reactions of cyclic o-phenylene and ethylene phosphites with hydroperoxides. Polarized phosphorus nuclei appear especially in the phosphonate and phosphate regions. Application of Kaptein's rule shows that these products are cage or escape products of secondary or tertiary radical pairs. Solvent molecules are involved in the formation of the tertiary radical pairs.The concentration of the products formed from polarized 31P nuclei is very low.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280515
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  • 7
    Electronic Resource
    Electronic Resource
    13C-NMR-spektroskopische Analyse von Gemischen Isomerer Alkyl-4-butylmorpholine (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 797-804 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C-N.M.R. Spectroscopical Analysis of Mixtures of Isomeric Alkyl-4-butylmorpholinesMixtures of isomeric alkyl-4-butylmorpholines 3 were prepared by the treatment of several 2,2′-dichloroalkyl ethers 1 (from the chlorination of alk-1-enes in the presence of ethylene oxide or propylene oxide) with butylamine and distinguished by 13C-n.m.r. The distribution of isomers of 3 is not changed in relation to that of 1 except 3g,g′.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280519
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  • 8
    Electronic Resource
    Electronic Resource
    Fotosensibilisierte Ausbleichung von Azomethinfarbstoffen (1988)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 204-212 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fotosensitized Fading of Azomethine DyesThe quantum yields of photofading of the azomethine dyes 1a - h were determined in the presence of the sensitizers benzophenone (B), michler's ketone (MK) and anthracen (A), in isopropanol and benzene. In isopropanol, excluding oxygen, the leuco dyes 5 are formed by benzophenone in high quantum yield (ΦBAr = 0.4). Photofading also takes place using Michler's ketone (ΦMKAr ≅ 3 · 10-3) and anthracene (ΦAAr ≅ 1 · 10-4), but 5 was not found. With benzophenone (Φ2AO ≅ 7 · 10-3), Micher's ketone (ΦMKO2 ≅ 1 · 10-3) and anthracene (ΦAO2 ≅ 1 · 10-4) as sensitizers the chromophore of 1a - h were destroyed, when oxygen was present. The photofading with benzophenone and Michler's ketone is a result of radicalic processes.Radical scavangers 8 and 9, therefore, give a strong decrease of the quantum yield of photofading. The photofading in benzene corresponds to the results in isopropanol considering the lower potential of this solvent for photoreduction processes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19883300206
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  • 9
    Electronic Resource
    Electronic Resource
    Spektralverhalten von Pyrazolin-5-on-Azomethinfarbstoffen - Quantenchemische Beschreibung der SubstituenteneinflüsseHerrn Prof. Dr. Dr. H. G. O. Becker zum 65. Geburtstag gewidmet (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 119-125 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absorption Behaviour of Pyrazoline-5-one Azomethine Dyes - Quantumchemical Description of the Influence of SubstituentsThe VIS absorption of the pyrazoline-5-one azomethine dyes 1a-h is measured in dependence of the substituents of the amino group.HMO calculations confirm that the „x- and y-bands“ have a strong charge transfer character. The absorptions in the visible region correspond to a transition from the HOMO mainly localized at the amino-substituted phenyl to the complex acceptor 4-imino-pyrazoline-5-one (“x-band”) or to the pyrazoline-5-one fragment (“y-band”). The calculated transition energies correlate with the values νmax of the x-band (r = 0.993). There is also a linear correlation between the square of the LCAO-MO coefficients in position 7 and 6 of the dye and εmax (r = 0.978).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290117
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  • 10
    Electronic Resource
    Electronic Resource
    Zur Kupplung von 4-substituierten 2-Pyrazolin-5-onen mit p-Chinondiiminkationen; Nachweis isokinetischer Beziehungen (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 217-223 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Coupling of 4-Substituted 2-Pyrazoline-5-ones with Quinone Diimine Cations; Detection of Isokinetic RelationsThe temperature dependence of the rate constant kK of the coupling reaction between pyrazoline-5-ones 1a-i and quinone diimine cations 2a, b is determined in dependence of the substituents at the coupling position (R3: —H, —N=N—Ar,—CHAr-pyrazoline-5-one). The activation enthalpies are between 7 and 60 kJ mol-1 and the activation entropies between -132 and -19 J mol-1 K-1. An isokinetic relation with β = 106°C is found and a rate determining combination of the carbanions of 1a-i with 2a, b is proposed. Contrary to this, the 2-pyrazolin-5-ones 1j-l, n (R3: —S—CNH2=NR) obey an isokinetic relation with β = -45°C. Taking into consideration the activation parameters, the low dependence of kK on the ionic strength, and the decrease of kK with the increase of the pK values of the couplers, a rate determining splitting off of R3 is assumed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290210
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