AbstractsChemistry

"The reduction of Ce(IV) in HC10₄ solutions by four polyaminocarboxylic acids, which are commonly used as chelating agents, has been studied by the stopped-flow technique. The rates of reduction first increase with increasing acidity, reach maxima which are characteristic of the chelating agent and the medium, then progressively decrease with increasing the acid concentration in the media. At their maximum reactivities, trans-1,2-diaminocyclohexane tetraacetic acid (CDTA) shows the highest reductive ability; this is followed by ethylenedinitrilotetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and finally nitrilotriacetic acid (NTA). The observed maxima can be qualitatively explained in terms of a mechanism which involves unhydrolyzed Ce⁴⁺ species and unprotonated polyaminocarboxylic acids. A comparison with the reactivities observed in H₂SO₄ media [S. B. Hanna, R. K. Hessley, w. H. Webb and w. R. Carroll, Z. Anal. Chem., in press (1971)] is presented and a mechanism for the EDTA oxidation, consistent with salt effects and the activation parameters, is advanced" – Abstract, page ii.