Addition of radicals to quinones—III. ESR study of some radical reactions of 2,6-dialkyl-1,4-benzoquinones

✍ Scribed by T.L. Simándi; A. Rockenbauer; F. Tüdős

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 365 KB
• Volume: 25
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(89)90193-6

✦ Synopsis

Reactions between 2,6-dialkyl-l,4-benzoquinones and various free radicals have been studied by ESR spectroscopy. The stable intermediates were identified on the basis of their spectra. It has been established that cyanoisopropyl, polystyryl and poly-(ct-methylstyryl) radicals attack at the oxygen atom of the quinone, whereas the radicals formed in the thermal decomposition of peroxides (benzoyl and acetyl) attack the C-----C double bond in the quinone ring. A mechanism is proposed for the latter process.

In continuation of earlier work [1, 2] with halogen substituted quinones, we have studied some new systems, reacting various 2,6-dialkyl-l,4-benzoquinones with active radicals formed in the thermal decomposition of benzoyl peroxide (BP), acetyl peroxide (AP) and azobisisobutyronitrile (AIBN). p-Benzoquinones with electron-accepter substituents react at the oxygen, as found earlier. It was interesting to find out how the nature of a substituent affects the radical reaction and especially the site of radical attack. The ESR spectra of the intermediate radicals were recorded in situ.