Mechanistic Study on the Oxidation of Promazine and Chlorpromazine by Hexaimidazolcobalt(III) in Acidic Aqueous Media |
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Authors: | Joanna Wi?niewska Przemys?aw Kita |
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Institution: | (1) Department of Chemistry, Nicolaus Copernicus University, Gagarina 7, 87-100, Toruń, Poland |
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Abstract: | The kinetics of the oxidation of promazine and chlorpromazine by hexaimidazolcobalt(III) were studied in the presence of a
large excess of cobalt(III) and H+ ions using u.v.–vis. spectroscopy (CoIII] = (1–6) × 10−3 m, ptz] = (2.5–10) × 10−5 m, H+] = 0.05–0.8 m, I = 1.0 m (H+, Na+, Cl−), T = 333–353 K, l = 1 cm). In each case, the reversible reaction leads to formation of cobalt(II) species and a stable cationic radical. A
linear dependence of the pseudo-first-order rate constant (kobs) on CoIII] with a non-zero intercept was established for both phenothiazine derivatives. A marked difference in the observed reaction
rate for promazine and chlorpromazine is associated with the difference in its ability to undergo oxidation and is consistent
with a trend in the redox potential changes for these reductants. The activation parameters for reactions studied were determined.
Mechanistic consequences of all the results are discussed. |
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