An electron spin resonance study of the addition reactions of arylsilyl and diphenylphosphino-radicals to para-quinones

Abstract

Arylsilyl radicals were found to add to a carbonyl oxygen of various p-quinones to produce siloxy-substituted phenoxyl radicals. Likewise the reaction of diphenylphosphino-radical with p-quinones produced similar phenoxyl radicals. For the unsymmetrical 2,6-di-t-butyl-p-benzoquinone both possible isomers of the triphenylsilyl adduct were observed, but while 4-triphenylsiloxy-2,6-di-t-butylphenoxyl radical persisted for months its isomer decayed within seconds. t-Butoxyl and carbon radicals did not appear to add to p-quinones. Consequently p-quinones appear to be excellent preferential spin traps for silyl and phosphino-radicals in solution.