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'Semiquinones' in keywords
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1986 (1)
1985 (2)
1983 (1)
1Author    HartmutB. Stegmann, Klaus Stolze, Klaus SchelflerRequires cookie*
 Title    ESR-Untersuchungen des Adrenalon-Semichinons und analoger Verbindungen ESR-Investigations of Adrenalone-Semiquinones and Related Compounds  
 Abstract    The autoxidation of adrenalone and other 4-acyl-catecholamines in the presence of diorganothalliumhydroxide are investigated by ESR-spectroscopy. On the basis of the counterion splitting and the proton coupling constants as well as the g-values a semi-quinone structure was established. By comparing several monosubstituted o-benzosemi-quinones an increment system for the assignment of the different proton coupling constants was developed. The agreement between experimental and calculated values is good for all compounds investigated. Prolonged autoxidation of adrenalone yields a stable para-magnetic secondary product. 
  Reference    Z. Naturforsch. 38b, 243—247 (1983); eingegangen am 1. September 1982 
  Published    1983 
  Keywords    Adrenalone, Semiquinones, ESR Spectra 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0243.pdf 
 Identifier    ZNB-1983-38b-0243 
 Volume    38 
2Author    HartmutB. Stegmann, Hoang Dao-Ba, Klaus Scheffler, MartinG. PeterRequires cookie*
 Title    ESR and ENDOR Investigations of Adrenochrome Semiquinone and Related Amino-1,2-Benzosemiquinone Radicals  
 Abstract    Dimethyl or diethylamine reacts very smoothly in ethanol solution with catechols to the corre­ sponding aminoquinones. The paramagnetic intermediates, the semiquinones, are investigated by ESR and E N D O R spectroscopy using the spin stabilisation technique with diarylthallium cations. The spectra of these radicals show clearly the thallium and nitrogen coupling and the hydrogen hyperfine structure. For some examples the signs of the proton coupling constants are determined by T RIPLE resonance experiments. The results indicate a negative spin density in one position of the unsymmetrically substituted radical 3. With the results obtained for the monocyclic aminosemiquinones the hyperfine structure of the adrenochrome semiquinone is analysed. 
  Reference    Z. Naturforsch. 40c, 531 (1985); received January 31/March 27 1985 
  Published    1985 
  Keywords    ESR-, ENDOR-Spectroscopy, Semiquinones, Adrenochrome 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0531.pdf 
 Identifier    ZNC-1985-40c-0531 
 Volume    40 
3Author    MartinG. Peter, HartmutB. Stegmann, Hoang Dao-Ba, Klaus SchefflerRequires cookie*
 Title      
 Abstract    ESR-spectra were recorded during the oxidation of N-acetyldopamine and N-ß-alanyldopamine in aqueous solutions. Semiquinone radicals were detected under conditions of spin stabilization by Z n2+ ions. The appearance of the spectra was the same in the presence or in the absence of proteins. No evidence was obtained for the formation of products that could have arisen eventual­ ly from intermolecular Michael-type addition of nitrogen nucleophiles. 
  Reference    Z. Naturforsch. 40c, 535—538 (1985); received January 31 1985 
  Published    1985 
  Keywords    ESR-Spectroscopy, Catecholamines, Semiquinones, Insect Cuticle 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0535.pdf 
 Identifier    ZNC-1985-40c-0535 
 Volume    40 
4Author    E. N. Esr, HartmutB. Stegmann, Klaus Stolze, Klaus SchefflerRequires cookie*
 Title    ESR-und ENDOR-Untersuchungen der Autoxidationsprodukte des Adrenalons und analoger Verbindungen Investigations of the A utoxidation Products of Adrenalone and Related Compounds  
 Abstract    The signs of the proton coupling constants of adrenalone sem iquinone and related compounds were determ ined by E N D O R and T R IP L E resonance studies, thereby verifying the increment system described in our previous paper [2], Com parison of the spin-distribution of several substi­ tuted acylcatechols showed the conform ational influence on the coupling constants due to mesomeric interaction of the carbonyl group with the arom atic 7r-system. A drenalone and other N -m onosubstituted catecholam ines showed rather stable secondary radi­ cals after the decay of the prim ary sem iquinone radical. They were identified as substituted dihydropyrazinium cation radicals after selective deuteration and comparison of their ESR-, EN D O R -and TRIPLE -resonance spectra with those of the non-deuterated species. They are formed by cyclic condensation of two molecules with subsequent oxidation. E in fü h ru n g 
  Reference    Z. Naturforsch. 41b, 776 (1986); eingegangen am 24. Januar 1986 
  Published    1986 
  Keywords    A drenalone, Semiquinones, ESR Spectra, E N D O R Spectra 
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 TEI-XML for    default:Reihe_B/41/ZNB-1986-41b-0776.pdf 
 Identifier    ZNB-1986-41b-0776 
 Volume    41