The factors affecting the stability of superoxide anion (O2?) in acetonitrile have been examined In the presence of oxygen O2? decayed rapidly. Oxygen uptake in the reaction and anal. of the products showed that mol. oxygen participated in and accelerated the reaction between O2? and acetonitrile. A possible mechanism based on the kinetic anal. is suggested. In the reaction of O2? with 2,2,6,6-tetramethyl-4-hydroxy-N-bromopiperidine (NB), the only product found is 2,2,6,6-tetramethyl-4-hydroxypiperidinyl-1-oxy radical which is characterized by its typical ESR spectrum. The reaction rate constant k1 of 1.33 ?102 dm3 mol-1 s-1 was determine by the UV stopped-flow technique. The results suggest that NB may be used as a specific spin trapping reagent.

Key words: ULTRAVIOLET SPECTROPHOTOMETRY, PIPERIDINE P, STABILITY, BROMINE COMPOUNDS, HYDROXY GROUP, NON-AQUEOUS SOLUTION, ACETONITRILE, ANHYDROUS, CATCHERS, SUPEROXIDE