Oxidation of methionine methyl ester in aqueous solution: A combined pulse radiolysis and quantum chemical study

A combined experimental and theoretical study is employed to elucidate one-electron oxidation mechanism of methionine methyl ester (MME) in aqueous solution. In neutral solution, OH radical reaction leads to the formation of a monomer transient species absorbing at 380 nm and a dimer transient species absorbing at 480 nm is formed in acidic solution. Quantum chemical calculations suggest that the transient species formed on reaction of OH radicals in neutral solution has 5-member ring structure. The transient absorption band formed on reaction of Cl 2 - or Br 2 - with MME is shown to be due to hemi bonded adduct between Cl or Br atoms and S in MME.