ASSOCIATION OF 6-HYDROXYQUINOLINE AND 8-HYDROXYQUINOLINE WITH AEROSOL-OT IN HEPTANE - COMPETITION WITH DIMERIZATION OF 8-HYDROXYQUINOLINE

The enhancement and shift of the fluorescence spectrum of 8-hydroxyqui noline (8-HQ) in heptane upon gradual additions of the anionic surfact ant aerosol-OT(AOT) allowed us to show that monomeric 8-HQ was progres sively associated to the polar heads via H-bonding. This association c ompetes with dimerization of 8-HQ in heptane which has been revealed b y us in a previous work using vapor pressure osmometry measurements. S imilar competition has been qualitatively reported by others in the ca se of 7-aza-indole. In the present work, a comparison between the beha viors of 8- and 6-hydroxyquinoline was undertaken because the position s of the -OH and greater than or equal to N functions preclude dimeriz ation in 6-hydroxyquinoline. This comparison resulted in the determina tions of the binding constant of 8-NQ to AOT, K-ass = 860 +/- 30, and of the dimerization constant in heptane, K-dim = (7.0 +/- 1.5) x 10(7) . Hence the dimers of 8-HQ in heptane, never reported before, turned o ut to be of outstanding stability. (C) 1998 Academic Press.