TY - JOUR
T1 - Reactions of B12r with Aliphatic Free Radicals
T2 - A Pulse-Radiolysis Study
AU - Mulac, William A.
AU - Meyerstein, Dan
PY - 1982
Y1 - 1982
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0012233653&partnerID=8YFLogxK
U2 - 10.1021/ja00379a014
DO - 10.1021/ja00379a014
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AN - SCOPUS:0012233653
SN - 0002-7863
VL - 104
SP - 4124
EP - 4128
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 15
ER -