S. Schulman, P. J. Kovi
Dec 1, 1973
Citations
0
Influential Citations
16
Citations
Journal
Analytica Chimica Acta
Abstract
The electronic absorption and fluorescence spectra of 1-hydroxy-2-naphthoic acid and 2-hydroxy-1-naphthoic acid were studied throughout the pH range in water and the Hammett acidity range in sulfurie acid. As in salicylic acid and 3-hydroxy-2-naphthoic acid an intramolecular hydrogen bond between the hydroxyl proton and the carboxyl group is evident from the small pH dependent shifts of the spectra of the neutral molecules, upon dissociation, and the anomalous pKa values. The neutral molecules undergo biprotonic phototautomerizations to the zwitterions, in their lowest excited singlet states, in moderately concentrated sulfuric acid. The anomalous shifts of the fluorescences of the neutral molecules upon dissociation, are attributed to the effects of dissociation and intramolecular hydrogen bonding, upon the 1La and 1Lb states. Mention is made of the possible utility of fluorimetric titrimetry for qualitative analysis at trace levels.