Manganese(III) geocomponents are commonly found in the soil environment, yet their roles in many biogeochemical processes remain unknown. In this study, we demonstrated that MnIII generated from the reaction of MnO 2 and oxalic acid caused rapid and extensive decompositions of a quinoxaline-di-N-oxide antibiotics, viz carbadox. The reaction occurred primarily at the quinoxaline-di-N-oxide moiety resulting in the removal of one - O from N1-oxide and formation of desoxycarbadox. The reaction rate was accelerated by increasing amounts of MnIII, carbadox and oxalate. The critical step in the overall reaction was the formation of a quinoxaline-di-N-oxide/MnIII/oxalate ternary complex in which Mn III functioned as the central complexing cation and electron conduit in which the arrangement of ligands facilitated electron transfer from oxalate to carbadox. In the complex, the C - C bond in oxalate was cleaved to create CO2-• radicals, followed by electron transfer to carbadox through the MnIII center. This proposed reaction mechanism is supported by the reaction products formed, reaction kinetics, and quantum mechanical calculations. The results obtained from this study suggest that naturally occurring MnIII-oxalic acid complexes could reductively decompose certain organic compounds in the environment such as the antibiotic quinoxaline-di-N-oxide.
All Science Journal Classification (ASJC) codes
- 化學 (全部)