Kinetics of excited-state proton-transfer reactions and proton-induced fluorescence quenching of 1-naphthol
(1N) and 2-octadecyl-1-naphthol (2O1N) in micellar solutions of cetyltrimethylammonium bromide (CTAB),
polyoxyethylene(23) lauryl ether (Brij 35), and sodium dodecyl sulfate (SDS) was studied by using stationary
and time-resolved fluorescence techniques. The ground-state acidity constant of 2O1N in cationic micelles of
CTAB was found to be significantly smaller than that of the parent compound (ΔpK = 0.5). However, similar
rate and equilibrium constants of the protolytic dissociation were obtained for 1N and 2O1N in the singlet
excited state. Effects of nonionic micelles of Brij 35 closely resemble those of CTAB. In anionic micelles of
SDS, the protolytic photodissociation was much slower for 2O1N than for 1N. The protonation rate for the
excited anions in micellar solutions increases by approximately 2 orders of magnitude in the series CTAB,
Brij 35, SDS. Excited-state kinetics was rationalized within the framework of a pseudophase model, which
included micellar effects on the proton-transfer equilibrium and interfacial diffusion of hydronium ions. The
electrostatic surface potential of charged micelles was estimated from the acidity constants of naphthols.