FORMATION AND REACTIVITY OF VINYLPEROXYL RADICALS IN AQUEOUS-SOLUTIONS

Vinyl, carboxyvinyl, and dicarboxyvinyl radicals were produced in irra diated aqueous solutions from acetylene and acetylenecarboxylic and ac etylenedicarboxylic acid by addition of H atom to the triple bond or b y reaction with e(aq)(-), followed by protonation. Vinyl and phenylvin yl radicals were produced by reductive dehalogenation of vinyl bromide and beta-bromostyrene with e(aq)(-). Ah these vinyl radicals react ra pidly with oxygen to produce the corresponding vinylperoxyl radicals. Vinylperoxyl radicals exhibit optical absorptions in the UV (lambda(ma x) 250-290 nm) and in the visible range. The peaks in the visible rang e were at 440 nm for unsubstituted vinylperoxyl radical, between 480 a nd 520 nm for carboxylated vinylperoxyl, depending on pH and-number of carboxyl groups, and at 540 and 690 mm for (2-phenylvinyl)peroxyl. Th ese vinylperoxyl radicals oxidize organic reductants such as 2,2'-azin obis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine; a scorbate, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid ( Trolox C) with rate constants between 4 x 10(5) and 2 x 10(9) L mol(-1 ) s(-1), depending on the radical and the reductant. Vinylperoxyl radi cals are more reactive than similarly substituted alkylperoxyl; carbox yl and phenyl substituents on the. vinyl group increase the reactivity of the vinylperoxyl radical.