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  • 1
    Electronic Resource
    Electronic Resource
    Photochemical Reactions of Triplet Methylene Blue with arene diazonium salts relative efficiency of the oxidation and the reduction mechanismsHerrn Prof. Dr. Dr. K. Schreiber zum 60. Geburtstag gewidmet (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 661-672 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants and efficiencies of the oxidative bleaching of triplet-excited methylene blue by different arene diazonium salts are determined by flash photolysis and stationary experiments.In the same way the rate constants of methylene blue photoreductions by diazabicylo[2,2,2]-octane (DABCO), sodium tetraphenyl borate (TPB), sodium ethylenediamine tetraacetate (EDTA), and allyl thiourea (ATU) are determined.According to these results TPB reduces methylene blue photochemically not exceedingly fast (ke = 1.5 × 107M-1s-1) but with a high efficiency (η = 0.8).At high diazonium salt concentrations (10-1 - 10-2 M), the oxidation and the reduction mechanisms of the triplet-methylene-blue sensitized dediazoniation of arene diazonium salts have similar efficiencies at high as well as at low light intensities.At low diazonium salt concentrations and with diazonium salts of low reactivity, the reduction mechanism is favoured over the oxidation mechanism.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280502
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  • 2
    Electronic Resource
    Electronic Resource
    Eigenschaften und thermische Reaktionen von Komplexen der Arendiazoniumsalze mit Kronenethern (1982)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 947-954 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Properties and Thermal Reactions from Complexes of Arene Diazonium Salts with Crown EthersIn contrast to 18-crown-6, the substituted crown ethers Benzo-18-crown-6, Dibenzo-18-crown-6, and Naphtho-18-crown-6 form in solution complexes with p-CH3—C6H4—N2+BF4-characterized by a broad charge transfer absorption up to 550 nm. The formation constants lg Kc are 2,32 2,16 and 1,44 for Benzo-, Dibenzo-, and Naphtho-18-crown-6, respectively. Formation enthalpy ΔH = -7,5 kJ/mol and entropy ΔS = +18 J/K mol are measured in the case of p-Cl—C6H4—N2+BF4- and Dibenzo-18-crown-6 (20°). Kc depends on substituents in the arene ring of the diazonium salt; ϱ = +0,8. Thermal dediazoniation in the presence of Crown ethers results in high yields of the corresponding arene. This is explained by a fast radical chain reaction between the diazonium salt and the polyether (Meerwein-Reduction).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19823240613
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  • 3
    Electronic Resource
    Electronic Resource
    Tietze, L. F. Eicher, Th: Reaktionen und Synthesen im organisch-chemischen Praktikum. 592 S., Format 16×23 cm, Stuttgart-New york:Georg Thieme Verlag 1981n, Paperback preis 54,- DM (1983)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 1047-1048 
    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.19833250626
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  • 4
    Electronic Resource
    Electronic Resource
    Photoinduzierte Elektronentransfer-Reaktionen von Komplexen der Arendiazoniumsalze mit KronenethernVortrag auf der Hauptjahrestagung der Chemischen Gesellschaft der DDR 1980 in Karl-Marx-Stadt. (1984)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 326 (1984), S. 92-100 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoinduced Electron Transfer-Reactions of Arenediazonium Ions Complexed with Crown EthersThe photolysis (full light of a medium pressure Hg-lamp) of p-methylbenzenediazonium-tetrafluoroborate in the presence of the crown ether 18-crown-6 (1) yields mainly the products of a heterolytic dediazoniation via arene cations as intermediates. The quantum yield ϕges of the photolysis from p-methoxybenzenediazonium-tetrafluoroborat in CH2Cl2 decreases in the presence of 18- crowns-6 (1) from 0.66 to 0.08. In contrast to 1, the photolysis of arenediazonium salts in the presence of dibenzo-18-crown-6 (3) yields mainly the products of a homolytic dediazoniation as a consequence of an electron transfer from 3 to the diazonium ion. ϕges of this reaction increases with decreasing wavelength of the exciting light from 0.09 (436 nm) to 0.32 (366 nm). this wavelength dependence is explained by formation of a correlated radical pair after excitation. In agreement with this situation a photo-CIDNP-effect is observed in the 15N-n.m.r.-spectra of isotopically labeled arenediazonium salts complexed by 3 and benzo-18-crown-6(2). No photo-CIDNP-effect is observed in the presence of 1. This different behaviour of the EDA-complexes formed by arenediazonium salts with the two different groups of crown ethers 1 and 2, 3 is discussed as a control of the electron transfer-reaction by the structure of the frontier orbitals.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19843260114
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  • 5
    Electronic Resource
    Electronic Resource
    Photooxidation von Arylazonaphtholen mit Singulett-Sauerstoff (1981)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 323 (1981), S. 957-964 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photooxidation of Arylazo-Naphtholes with Singlet OxygenThe reaction of p-substituted 4-arylazo-1-naphtholes 1 and 1-arylazo-2-naptholes 5 with singlet oxygen (produced by methylene blue-sensitized photolysis) has been studied spectroscopically in methanol as a solvent. The rate constants of dye bleaching are the same, irrespective whether the extinctions of the azo or the hydrazone forms of the tautomeric systems are measured. Both reaction series 1 and 5 afford linear Hammett plots, which is discussed in the light of the azohydrazone equilibrium of the dyes and an „ene“ mechanism of the reaction with singlet oxygen. It could be shown by short-time spectroscopy that the azo-hydrazone isomerization proceeds much faster than the attack of singlet oxygen on the hydrazone form, which explains all observed facts.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19813230614
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  • 6
    Electronic Resource
    Electronic Resource
    15N- und 13 C-NMR-chemische Verschiebungen sowie 13C-1H-, 13C-15N- und 15N-15N-Spin-Spin-Kopplungskonstanten para-substituierter Benzendiazoniumsalze (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 63-79 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitrogen-15 and Carbon-13 Chemical Shifts and 13C-1H, 13C-15N and 15N-15N Coupling Constants of Parasubstituted Arene Diazonium SaltsNitrogen-15 and carbon-13 chemical shifts and 13C-1H,13C-15N and 15N-15N coupling constants of 15N-enriched p-substituted arene diazonium salts are reported and within the ΔE-approximation investigated. It is shown that changes of ΔE should be taken into account when considering variation of the nitrogen-15 chemical shifts. The influence of substituent effects was discussed within the DSP (dual substituent parameter)-approach.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270109
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  • 7
    Electronic Resource
    Electronic Resource
    Photoinduzierte Elektronenübertragungsreaktionen zwischen aromatischen Diazoniumkationen und Anionen (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 399-410 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoinduced Electron Transfer between Arenediazonium Cations and AnionsAnions X⊖ can act as donors in electron transfer reactions to photoexcited arenediazonium ions. The yield of the arene formed in this reaction increases with decreasing electrochemical oxidation potential EoxD of X⊖ (X⊖ = BPh4⊖, Br⊖, HOOC—COO⊖, Cl⊖, BF4⊖). The oxidized donor X· (Cl·, ·COO⊖) and aryl radicals Ar· benig intermediates of the reductive dediazoniation of ArN2⊖ can be detected by spin trapping with nitrosodurene (ND) and phenyl-tert-butylnitrone (PBN). A solvent effect in the electron transfer reaction is interpreted in terms of ion pairing, where the electron transfer is favored by preorientation and a short distance between the electron donor and the acceptor previous to excitation of ArN2⊖ by light.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270306
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  • 8
    Electronic Resource
    Electronic Resource
    Solvenseffekte bei der Photoinduzierten Elektronenübertragung von ungeladenen Donatoren auf Arendiazoniumsalze (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 411-421 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent Effects in the Photoinduced Electron Transfer Reaction of Uncharged Donors with Arenediazonium SaltsIn the photochemical electron transfer reactions to arene diazonium salts no strong Coulomb forces arise but the rate constants possibly vary in dependence on the state of the diazonium salt (tight ion pair in nonpolar solvents or free diazonium cations). This problem is studied in the present work using anthracene and tetracene, respectively, as electron donors. They react in their S1 states diffusion-controlled with ion pairs ArN2⊖ BF4⊖, whereas the respective triplet reactions proceed up to 103 times more slowly. These rates are not significantly influenced by the dielectric properties of the solvent. Thus, ion pairing of the diazonium salts in solvents of low polarity has no screening effect on the electron transfer.This behavior is explained including electrostatic effects into the MARCUS theory of outer sphere electron transfer processes. No indication of a Marcus inverted region was found.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270307
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  • 9
    Electronic Resource
    Electronic Resource
    Photochemical Dediazoniation of Arene Diazonium Salts sensitized by zinc phthalocyanine tetra(sulfomorpholide)Herrn Prof. Dr. R. Mayer zum 60. Geburtstag gewidmet (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 729-740 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photo-excited zinc phthalocyanine tetra(sulfomorpholide) (ZnPcTSM) sensitizes the dediazoniation of arene diazonium salts via electron transfer. 1ZnPcTSM* reacts with p-methyl-, p-methoxy-, and p-diethylamino benzenediazonium tetrafluoroborate, respectively, diffusion-controlled, 3ZnPcTSM* with rate constants 3.3 × 107, 8.5 × 107, and 1.1 × 108 M-1 s-1.Quantum yields of the dye bleaching by p-methoxy benzenediazonium tetrafluoroborate show that the singlet reaction proceeds due to symmetry-allowed back electron transfer with very low efficiency, whereas the triplet reaction reaches the ISC quantum yield at [ArN2⊕] ≍ 10-3 M.In the triplet reaction an exciplex is formed as proved by the temperature dependence of the quenching rate constants and direct spectroscopic determination (τexciplex = 157 μs). From ΔG≠ of the quenching reaction the solvation reorganization parameter λ0 and the reaction distance (r = 0.37 nm) are calculated.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280511
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  • 10
    Electronic Resource
    Electronic Resource
    Fluoreszenzlöschung aromatischer Verbindungen durch Diazoniumkationen in wäßrigen Lösungen von Natriumpolyvinysulfat (1987)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 329 (1987), S. 95-100 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quenching of Fluorescence of Aromatic Compounds by Diazonium Cations in Aqueous Solutions of PolyelectrolytesThe absorption and fluorescence spectra, and lifetimes of sodiumpyrene-3-sulfonate, N-phenylacridone and acridizinium perchlorate have been measured in the absence and in the presence of sodiumpolyvinylsulfate. A study is made of the quenching by diazonium ions of the fluorescence of the aromatic compounds. The results of Stern-Volmer plots are discussed by a micro-heterogeneous model and compared with results in homogeneous solutions. It is suggested that contributions of quencher and aromatic compound in both polyelectrolyte and aqueous phases are important.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19873290113
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