Kinetics and Possible Mechanisms of the Ce(IY) Oxidation of EDTA, CDTA, DTPA and NTA in Perchloric Acid Media*
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چکیده
The rates of oxidation of four chelating agents with Ce(IV) in HC104 solutions, have been studied by the stopped-flow technique. The rates first increase with increasing acidity, reach maxima which are characteristic of the chelating agent and the medium, then progressively decrease with further increasing acid concentration. At their maximum reactivities, the tendencies for oxidation decrease in the following order: 2rans-l,2-diaminocyclohexane tetraacetic acid (CDTA) > ethylenedinitrilotetraacetic acid (EDTA) > diethylenetriaminepentaacetic acid (DTPA) > nitrilotriacetic acid (NTA). A mech anism for the oxidation of EDTA, involving Ce4+ and Ce(OH)3+ and both unprotonated and monoprotonated chelating agent, is proposed.
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