Acid-base and tautomeric equilibria of harmol in the ground and first excited singlet states
1985; Elsevier BV; Volume: 31; Issue: 2-3 Linguagem: Inglês
10.1016/0047-2670(85)85094-2
ISSN1873-2658
Autores Tópico(s)Chemical synthesis and alkaloids
ResumoAbstract Four molecular species have been identified from the acid-base equilibria of the alkaloid harmol by using absorption and fluorescence spectroscopy. The p K a values which govern the acid-base equilibria in the ground electronic state have also been derived from the absorption spectra. The corresponding p K a values for the first excited singlet state equilibria have been calculated by means of the Forster equation. Through auxiliary experiments in the dispersed solid phase, it has been possible to separate the emission maxima of the neutral and zwitterionic species in aqueous media. As occurs in harmalol, in the first excited singlet state the hydroxy group is more acidic and the ring nitrogen atom more basic than in the ground state.
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