Nonlinear instabilities in the light-mediated bromate–4-aminophenol reaction

The kinetics and mechanism of the photo-illuminated bromate–4-aminophenol (AP) reaction were investigated in this report, in which chemical oscillations were observed over broad reaction conditions when the applied light intensity was above a threshold level. Besides Pt and bromide potentials, absorption spectra also exhibit large amplitude oscillations within a wavelength between 300 and 440 nm. Phase diagrams in a three-dimensional concentration space illustrate that the oscillatory behaviour is more sensitive to the ratio of [AP]/[BrO3−] than their actual concentrations. The induction time and number of oscillations show different dependence on the concentrations of the initial reactants. Several intermediates were identified by mass spectrometry, 1H NMR and 13C NMR methods, and possible mechanisms leading to the formation of those intermediates were discussed.