Polarographic and voltammetric behavior of the antibiotic cefetamet; Reduction of the methoxyimino group

Evaluation of DC polarographic i-E curves and analogous curves obtained by cyclic voltammetry in aqueous buffers as well as in buffers containing 30% v/v ethanol indicated that the methoxyimino group of cefetamet is reduced on DME and HDME in the following way: the methoxyimino group can be at the electrode surface rapidly protonated up to pH about 9. In the protonated form of the grouping (> C= NH - OCH3)(+), the OCH3 is cleaved off in the first two-electron step. The resulting imine is in equilibrium with its protonated form, which is reduced in a second two-electron step. At pH higher than about 10, the unprotonated form of the methoxyimino group is reduced in a single four-electron step to amine. Studies using cyclic voltammetry were complicated by adsorption phenomena.