| Abstract
| - The influence of oxygen in Belousov−Zhabotinskysystems with substituted malonic acid derivatives RMA(R = H, Me, Et, Bu, phenyl, and benzyl) has been studied. Asignificant influence of oxygen and organicsubstrate has also been found for the autocatalytic oxidation of thecatalyst by bromate. In both the presenceand the absence of RMA, oxygen always increases inflection times of theautocatalysis when compared withanaerobic conditions (argon bubbling). In general, period lengthsP of RMA−BZ systems increase withincreasing Taft σ* constants of substitutent R and a linearlog P − σ* relationship has been found. Inaerobicconditions (oxygen bubbling) the MA−BZ system is an exception becausemalonic acid (MA) BZ periodlengths are, at these conditions, significantly lower and deviate fromthe linear log P − σ* relationship.Thedeviation appears to be related to the increased release of bromide ionwhen MA−BZ systems come incontact with oxygen. Model computations indicate that the decreasein inflection time of the autocatalysis isrelated to the scavenging of BrO2 radicals, probably byRMA• and RMAOO• radicals. The increaseof periodlengths in RMA−BZ systems with increasing σ* values appears to berelated to the bromination/enolizationof the organic substrate as the determined enolization rates of RMAshow.
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