Evidence for the addition of the superoxide anion to the anti-oxidant n-propyl gallate in aqueous solution.

n-Propyl gallate reacts with the superoxide radical anion in aqueous solution (k = 5.1 x 10(5) mol-1 dm3 s-1). The spectrum of the transient species so formed has been measured (absorbance maximum at 550 nm, epsilon = 1360 mol-1 dm3 cm-1). Electron or H atom transfer processes as well as proton abstraction have been excluded as possible mechanisms, and it is proposed that an addition reaction takes place.