Second-order combination reactions of phenoxyl radicals

摘要: Phenoxyl radicals, when produced pulse radiolytically at concentrations > 10{sup {minus}4} M, combine in second-order processes to give 2,2{prime}-, 2,4{prime}-, and 4,4{prime}-dihydroxybiphenyl as the predominant products. The ratios of these products observed under a variety conditions, 0.73:1.73:1.00, indicate that radical combination ortho para positions ring occurs statistically with, however, reaction site favored by factor 2.4 over site. This ratio is considerably greater than 1.55 unpaired spin populations two sites indicated ESR data. There essentially no meta position where population negative. Approximately 10% radicals couple oxygen yield 2- 4-phenoxyphenol. yields are, lower might be expected from 0.2 on atom phenoxyl. It clear factors addition are important controlling processes. Under optimum conditions five account for {approx}90% phenoxyl initially so electronic disproportionation or coupling form diphenyl peroxide relatively unimportant. Multiple-pulsemore » experiments show after build up comparable radical, secondary electron-transfer reactions lead more complex In studies with {gamma}-rays low-dose rates predominantly react simple very low.« less