INFLUENCE OF OXYGEN AND ORGANIC SUBSTRATE ON OSCILLATIONS AND AUTOCATALYSIS IN THE BELOUSOV-ZHABOTINSKY REACTION

The influence of oxygen in Belousov-Zhabotinsky systems with substitut ed malonic acid derivatives RMA (R = H, Me, Et, Bu, phenyl, and benzyl ) has been studied. A significant influence of oxygen and organic subs trate has also been found for the autocatalytic oxidation of the catal yst by bromate. In both the presence and the absence of RMA, oxygen al ways increases inflection times of the autocatalysis when compared wit h anaerobic conditions (argon bubbling). In general, period lengths P of RMA-BZ systems increase with increasing Taft sigma constants of su bstitutent R and a linear log P - sigma relationship has been found. In aerobic conditions (oxygen bubbling) the MA-BZ system is an excepti on because malonic acid (MA) BZ period lengths are, at these condition s, significantly lower and deviate from the linear log P - sigma rela tionship. The deviation appears to be related to the increased release of bromide ion when MA-BZ systems come in contact with oxygen. Model computations indicate that the decrease in inflection time of the auto catalysis is related to the scavenging of BrO2 radicals, probably by R MA(.) and RMAOO(.) radicals. The increase of period lengths in RMA-BZ systems with increasing sigma values appears to be related to the bro mination/enolization of the organic substrate as the determined enoliz ation rates of RMA show.