Abstract
The kinetics and mechanisms of the degradation of carboquone (CQ) in aqueous solution were studied and compared with those of 2, 5-bis (1-aziridinyl)-3, 6-dialkyl-1, 4-benzoquinones [EBs : R=-H (EB); -CH3 (MEB); -CH (CH3)2 (IPEB)] determined previously. The degradation of CQ was essentially similar to those of EBs : it followed pseudo first-order kinetics (specific acid-base catalysis), and involved the hydrolytic cleavage of aziridine rings in acidic solutions, the substitution of aziridine rings by hydroxyl ion (radical) in basic solutions and a combination of these two mechanisms in solutions of neutral pH. High performance liquid chromatography patterns of CQ solutions at acidic pH gave two peaks corresponding to two intermediate compounds with one aziridine ring and one hydroxyethylamino group (due to the asymmetrical structure of CQ). However, we could not identify each peak component, or estimate which aziridine ring (at the 2 or 5 position of CQ) was unreacted. This was also the case for the two intermediate compounds with one aziridine ring and one hydroxyl group observed in CQ solutions at basic pH. Kinetic studies of MEB and the two intermediate compounds obtained in acidic solutions by thin-layer chromatography separation made it possible to estimate the chemical structures of these four intermediate compounds.
