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

William A. Mulac; Dan Meyerstein

doi:10.1021/ja00379a014

Reactions of B_12r with Aliphatic Free Radicals: A Pulse-Radiolysis Study

William A. Mulac, Dan Meyerstein

Department of Chemistry

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Abstract

The spectra of the intermediates formed in the reactions of B_12r 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 B_12r to B_12a, via an inner-sphere mechanism, and CO₂⁻ reduces B_12r to B_12s. All the aliphatic free radicals studied, R, react with B_12r, yielding as the first product a pseudocoenzyme denoted C^III-R. Co^III-CH₂C(CH₃)₂OH is stable for over a second in the pH range 3–10 as is Co^III-CH₂CHO. The latter compound hydrolyzes in acid solutions to yield B_12a and CH₃CHO. Co^III-C(CH₃)₂OH and Co^III-CH(OH)CH₂OH decompose heterolytically to yield mainly B_12s; a side reaction that probably yields Co^III-H via a β-hydride shift is also observed. The kinetics of decomposition of Co^III-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 language	English
Pages (from-to)	4124-4128
Number of pages	5
Journal	Journal of the American Chemical Society
Volume	104
Issue number	15
DOIs	https://doi.org/10.1021/ja00379a014
State	Published - 1 Jan 1982

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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title = "Reactions of B12r with Aliphatic Free Radicals: A Pulse-Radiolysis Study",

abstract = "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.",

author = "Mulac, {William A.} and Dan Meyerstein",

year = "1982",

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doi = "10.1021/ja00379a014",

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volume = "104",

pages = "4124--4128",

journal = "Journal of the American Chemical Society",

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T1 - Reactions of B12r with Aliphatic Free Radicals

T2 - A Pulse-Radiolysis Study

AU - Mulac, William A.

AU - Meyerstein, Dan

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Y1 - 1982/1/1

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.

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ER -

Reactions of B_12r with Aliphatic Free Radicals: A Pulse-Radiolysis Study

Abstract

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