Spectroscopic Characterization of Some Chromone Azo Dyes

Abstract

Chromone azo dyes of 6-formyl-7-hydroxy-5-methoxy-2-methylchromone

(I), 5,7-dihydroxy-6-formyl-2-methylchromone (II) and 5,7-dihydroxy-

2,6-dimethylchromone (III) were prepared. The chromone azo

dyes were characterized by elemental analysis, IR, ¹H NMR and mass

spectra. IR and ¹H NMR indicate the presence of hydrogen bond between

hydroxyl group in position seven and the formyl group in position six

(Ia-Id). Also a hydrogen bonding between a hydroxyl group in position

five and the chromone carbonyl in position four is possible (IIa-d and

IIIa-d). The mass spectra indicate that molecular ions of some chromone

azo dyes were highly unstable, while the molecular ion was observed in

other cases. The fragmentation patterns indicate retro Diels-Alder reaction

in some cases.