Zur Prototropie von Phaeophytin a / On the Prototropy of Pheophytin a
| Autor: | Fritz Hindelang, Valentin Zanker, Ernst Rudolph |
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| Rok vydání: | 1973 |
| Předmět: | |
| Zdroj: | Zeitschrift für Naturforschung B. 28:650-655 |
| ISSN: | 1865-7117 0932-0776 |
| Popis: | Additionally to the neutral and dicationic configuration for pheophytin a the monocation and monoanion can also be determined and characterized by means of absorption and fluorescence polarisation spectroscopy, by its relative aqueous solubility, and by its behavior in the electric field. The typical absorption- and APF-spectra for these prototropic configurations exist at the following normalities: > 2N HCl(pK ≈0) for the dication, 1.0-1.7 N HCl(pK ≈ 1.6) for the monocation, 0.1ɴ HCl—0.0003ɴ NaOH for the neutral configuration, and 0.3ɴ NaOH(pK ≈8,5) for the monoanion. Due to the quickly starting secondary reactions at elevated alkaline pH, the diaions cannot be proved definitely. At the transition monoanion →neutral configuration → monocation → dication, the position of the red band remains nearly constant (changes being < 150 cm-1); in contrast, the bands 2 and 3 as well as the Bx and By transition of the Soret band are considerably shifted bathochromatically (1200-2000 cm-1); from this fact it may be concluded that there is an inner ring oscillator with participation of the N-atoms. In the same sequence the intensity of band 3 decreases by approx. 40% and that of band 2 increases by the same value; in the ionic state the intensity of the red band and Soret band is at a maximum. |
| Databáze: | OpenAIRE |
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