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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have