FORMATION AND REACTIVITY OF PYRIDYLPEROXYL RADICALS IN SOLUTION

2-Pyridyl radicals were produced by the reaction of 2-chloro- or 2-bro mopyridine with solvated electrons (k similar to 10(10) L mol(-1) s(-1 )) and reacted rapidly with oxygen (k = 2.2 x 10(9) L mol(-1) s(-1)) t o produce the 2-pyridylperoxyl radical. This radical exhibits optical absorption in the visible range, with lambda(max) at 440 nm. 2-Pyridyl peroxyl radical is a fairly strong oxidant, which reacts with 2,2'-azi nobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid(Trolox C) b y one-electron oxidation. The rate constants k for these reactions, de termined from the rate of formation of the one-electron oxidation prod ucts as a function of substrate concentration, vary between 2 x 10(6) and 2 x 10(9) L mol(-1) s(-1) in various solvent mixtures. For each su bstrate, a good correlation was found between log k and the cohesive p ressure of the solvent or solvent mixture, as found before for CCl3O2. radical reactions in nearly neat solvents. 3-Bromo, 3-chloro-, and 4- chloropyridine also reacted rapidly with solvated electrons, but their radical anions underwent protonation on the nitrogen in competition w ith the dehalogenation process. Therefore, no pyridylperoxyl radicals were formed from these species in aqueous solutions and only partial y ield was found in neat methanol.