Oxidation of L-Glutamine by Bis(hydrogenperiodato)argentate(III) Complex Anion:Kinetics and Mechanism

In an alkaline medium,oxidation of Gln by bis(hydrogenperiodato)argentate(Ⅲ) complex anion([Ag(HIO6)2]5-) results in both decarboxylation and deamination of Gln,giving rise to an oxidation product:H2NCOCH2CH2CHO;the oxidation product has been identified by chemical method and mass spectrometry.The oxidation reaction displays an overall second-order kinetics:first-order to both Ag(Ⅲ) and Gln,respectively.The observed second-order rate constants(k′),decreasing with increasing tot and increasing with increasing the ionic strength,are virtually invariable with the variation of .A reaction mechanism has been suggested to involve an pre-equilibrium between [Ag(HIO6)2]5-and [Ag(HIO6)(H2O)(OH)]2-;in two rate-determining steps,both the Ag(Ⅲ) species are reduced simultaneously by Gln.A rate expression has been derived and moreover,the rate constants for the rate-determining steps have been deduced and their corresponding activation parameters have been calculated.The mode for electron transfer process is discussed in detail.