A new method to study antioxidant capability:: Hydrogen transfer from phenols to a prefluorescent nitroxide

[ABSTRACT] Rate constants for hydrogen abstraction from phenols by a prefluorescent-TEMPO probe are reported. The nitroxide is employed as a potential model of peroxyl radicals. The probe works by nitroxide suppression of the fluorescence of the chromophore. The fluorescence is restored when the nitroxide abstracts a hydrogen atom to produce the diamagnetic hydroxylamine. The phenols studied in this project exhibited rate constants between 0.003 and 0.2 M-1 s(-1). A deuterium isotope effect of 10 for TROLOX confirms that the mechanism is dominated by hydrogen transfer.