New Experimental Insights into the Bromate – 4-Aminophenol Photochemical Oscillations

Abstract

Abstract In this research, it was found that following the photo-dissolution of the intermediate product N-bromo-1,4-benzoquinone-4-imine in the bromate – 4-aminophenol reaction, removal of illumination may allow the system to exhibit spontaneous chemical oscillations. This new observation complements the earlier report that the bromate – 4-aminophenol reaction could only oscillate under continuous illumination. Our exploration illustrates that the initial concentrations of bromate, 4-aminophenol and sulfuric acid have great influence on whether or not the system requires constant illumination for exhibiting oscillatory behavior. There is indeed an optimal illumination time interval at which the subsequently un-illuminated system would exhibit a large number of high frequency oscillations with or without an induction time period. Similar influences were also observed in the presence of cerium, in which the system exhibited sequential oscillations. Being able to respond to light in both a negative and constructive way makes this oscillatory system an attractive model for investigating perturbed nonlinear reaction dynamics.