Radical pair formation in γ-irradiated chloroform at 77 K

✍ Scribed by Shiro Konishi; Mikio Hoshino; Masashi Imamura

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 166 KB
• Volume: 82
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(81)85142-1

✦ Synopsis

Radical pair formation in

r&radiated chloroform at 77 K has been revealed by ESR spectra characteristic of triplet species, whereas no triplet spectra have been detected for other chlorinated methanes and bromoform. When solid-state radiolysis is performed on organic compounds at low temperatures, some of the reaction intermediates are trapped. Information on the trapped species provides clues to elucidate local structures of the irradiated solids and the mechanisms of radiationinduced reactions. Trapped species are isolated radicals in most cases. There have been, however, reports on the pairwise trapping of radicals evidenced by triplet ESR spectra [l-l 0] . The trapping of radical pairs has been found so far mostly in solids of relatively complex molecules. Only methane Fang C, compounds gives CH, .__ H [2] and CH3 .__ CH, [lo] pairs when irradiated at 4.2 K, but they disappear on raising the temperature. Thus, no C, compounds have been reported to yield radical pairs on irradiation at temperatures higher than cryogenic ones. This paper reports the ESR detection of radical pairs produced in polycrystalJine chloroform by 7 irradiation at 77 K. The chloroform dried over molecular sieve 4A andi degassed by freeze-pump-thaw cycles