Mechanism of the oxidative degradation of dibenzoazepine derivatives via manganese(III) complexes in acidic phosphate media

Abstract

The oxidative degradation of tricyclic antidepressants (TCA) was studied in the presence of a large excess of the oxidizing agents, manganese(III)- pyrophosphate (P2O74-), phosphate (PO 43-), in acidic media. The products were detected and identified using UV-Vis, ESI-MS and IR methods. The reaction between dibenz[b,f]azepines and manganese(III) ions proceeded via two consecutive reactions: first, acridine analogues were formed, and then a dealkylation process resulted in the formation of unsubstituted acridine. The kinetics of the first degradation step of the TCAs was investigated independently of the slower dealkylation step. The pseudo-first order rate constants (k obs) were determined for the first degradation process. The reaction between 10,11-dihydro-5H-dibenz[b,f]azepines and the manganese(III) ion resulted in oxidative dehydrogenation, which proceeded via the formation of two intermediates: a free organic radical and a dimeric dication. Further oxidation of the second intermediate led to a positively charged radical dimer as a single final product. Simultaneously, two other substituent cleavage degradation processes occurred, which led to two dimeric derivatives. The kinetic traces were determined to be zeroth order. © 2012 The Author(s).