Reactions of B12r with Aliphatic Free Radicals: A Pulse-Radiolysis Study

William A. Mulac, Dan Meyerstein

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28 Scopus citations


The spectra of the intermediates formed in the reactions of B12r with the free radicals Br2·, CO2·, CH2C(CH3)2OH, ·C(CH3)2OH, ·CH2CHO, and ·CH(OH)CH2OH are reported. The results indicate that Br2·oxidizes B12r to B12a, via an inner-sphere mechanism, and CO2 reduces B12r to B12s. All the aliphatic free radicals studied, R, react with B12r, yielding as the first product a pseudocoenzyme denoted CIII-R. CoIII-CH2C(CH3)2OH is stable for over a second in the pH range 3–10 as is CoIII-CH2CHO. The latter compound hydrolyzes in acid solutions to yield B12a and CH3CHO. CoIII-C(CH3)2OH and CoIII-CH(OH)CH2OH decompose heterolytically to yield mainly B12s; a side reaction that probably yields CoIII-H via a β-hydride shift is also observed. The kinetics of decomposition of CoIII-CH(OH)CH2OH in neutral solutions are reported. No water elimination from the latter intermediate occurs. The reasons for the latter observation are discussed.

Original languageEnglish
Pages (from-to)4124-4128
Number of pages5
JournalJournal of the American Chemical Society
Issue number15
StatePublished - 1 Jan 1982

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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