| | 2 | Author
| HartmutB. Stegmann, Hoang Dao-Ba, Klaus Scheffler, MartinG. Peter | Requires 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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| default:Reihe_C/40/ZNC-1985-40c-0531.pdf | | | | Identifier
| ZNC-1985-40c-0531 | | | | Volume
| 40 | |
| 3 | Author
| MartinG. Peter, HartmutB. Stegmann, Hoang Dao-Ba, Klaus Scheffler | Requires 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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| default:Reihe_C/40/ZNC-1985-40c-0535.pdf | | | | Identifier
| ZNC-1985-40c-0535 | | | | Volume
| 40 | |
| 4 | Author
| E. N. Esr, HartmutB. Stegmann, Klaus Stolze, Klaus Scheffler | Requires 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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| default:Reihe_B/41/ZNB-1986-41b-0776.pdf | | | | Identifier
| ZNB-1986-41b-0776 | | | | Volume
| 41 | |
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