Date on Master's Thesis/Doctoral Dissertation

8-2019

Document Type

Master's Thesis

Degree Name

M.S.

Department

Chemistry

Degree Program

Chemistry, MS

Committee Chair

Kozlowski, Pawel

Committee Co-Chair (if applicable)

Thompson, Lee

Committee Member

Thompson, Lee

Committee Member

Luzzio, Frederic

Committee Member

Sathitsuksanoh, Noppadon

Author's Keywords

MeCbl,Photolysis; TS; Aerobic

Abstract

The photolysis of methylcobalamin (coenzyme B12) results in homolytic cleavage of the Co-C bond, forming cob(II)alamin and the Co(II)/CH3 radical pair (RP) which further react with O2 to form the intermediate (R-O-O-Cbl) that involves in the aerobic photolysis. It has been suggested that the key intermediate (R-O-O-Cbl) involves in aerobic photolysis is the insertion of O2 between the Co-C bond. Clearly, the exposure of light is needed to induce the activation Co-C bond for generating the Co(II)/CH3 radical pair (RP). The intermediate (R-O-O-Cbl) undergoes further decomposition to aldehyde as the final product of aerobic photolysis in presence of a water molecule. In the decomposition of the R-O-O-Cbl intermediate, the proton migrates along a contingent way, and the energy barrier for the transition state has been lowered when compared with the corresponding energy in a no water-involved reaction. The results have verified the presumption that one water molecule can assist to get the whole reaction. Since the presence of water molecule can help to relax the strain in a system and incredibly lower the energy barrier, the reactions in the presence of water are preferable to the no-water-involved ones. This is supported by a detailed theoretical investigation of the products initially formed when aqueous, homolytically-cleaved MeCbl reacts with molecular oxygen and a detailed description of the behavior of those products proceeding to photolysis.

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