Free radical induced one-electron oxidation of the phenothiazines chlorpromazine and promethazine

authored by: Detlef Bahnemann, Klaus Dieter Asmus, Robin L. Willson
Abstract: Absolute rate constants have been measured for the reactions of the protonated forms of chlorpromazine and promethazine, CZH⁺ and PZH⁺, with the electrophilic radicals ^.OH, Br ₂^-., (SCN)₂^-., I₂ ^-., N₃^., Tl²⁺, Tl(OH)⁺, (t-C₄H₉S t-C₄H₉)^+., (CH₃SSCH₃)^+., and lipoate^+. in the pH range 2-8. Values for these one-electron oxidations vary from k = 3.1 × 10⁸ mol^-1 dm³ s^-1 for [(t-C ₄H₉S t-C₄H₉)^+. + PZH ⁺] to 5.5 × 10⁹ mol^-1 dm³ s^-1 for (Br₂^-. + CZH⁺). The yields of the oxidation products, PTZH^2+., vary from 28% for (^.OH + CZH⁺) to 97% for [(SCN)₂^.- + CZH ⁺]. The PTZH^2+. radical cations exhibit characteristic absorption spectra with two maxima around 270 and 510 nm, and extinction coefficients of Sε(CZH^2+.) = 56 000 mol^-1 dm ³ cm^-1 at 270 nm and 12 000 mol^-1 dm ³ cm^-1 at 510 nm, and ε(PZH^2+.) = 62 500 mol^-1 dm³ cm^-1 at 265 nm and 9 500 mol ^-1 dm³ cm^-1 at 505 nm. A transient absorption around 350 nm observed in the reaction of the phenothiazines with hydroxyl radicals is most probably the ^.OH-adduct, PTZH(OH)^+.. The mechanism of the ^.OH-radical-induced oxidation of phenothiazines suggested in an earlier publication has been confirmed and enlarged.
External Organisation(s): Helmholtz-Zentrum Berlin für Materialien und Energie (HZB)
Brunel University
Type: Article
Journal: Journal of the Chemical Society, Perkin Transactions 2
Pages: 1661-1668
No. of pages: 8
ISSN: 1472-779X
Publication date: 1983
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: General Chemistry
Electronic version(s): https://doi.org/10.1039/P29830001661 (Access: Unknown)

BibTeX

@article{215717ae8b854e64850b200963ae647e,
title = "Free radical induced one-electron oxidation of the phenothiazines chlorpromazine and promethazine",
abstract = "Absolute rate constants have been measured for the reactions of the protonated forms of chlorpromazine and promethazine, CZH+ and PZH+, with the electrophilic radicals .OH, Br 2-., (SCN)2-., I2 -., N3., Tl2+, Tl(OH)+, (t-C4H9S t-C4H9)+., (CH3SSCH3)+., and lipoate+. in the pH range 2-8. Values for these one-electron oxidations vary from k = 3.1 × 108 mol-1 dm3 s-1 for [(t-C 4H9S t-C4H9)+. + PZH +] to 5.5 × 109 mol-1 dm3 s-1 for (Br2-. + CZH+). The yields of the oxidation products, PTZH2+., vary from 28% for (.OH + CZH+) to 97% for [(SCN)2.- + CZH +]. The PTZH2+. radical cations exhibit characteristic absorption spectra with two maxima around 270 and 510 nm, and extinction coefficients of Sε(CZH2+.) = 56 000 mol-1 dm 3 cm-1 at 270 nm and 12 000 mol-1 dm 3 cm-1 at 510 nm, and ε(PZH2+.) = 62 500 mol-1 dm3 cm-1 at 265 nm and 9 500 mol -1 dm3 cm-1 at 505 nm. A transient absorption around 350 nm observed in the reaction of the phenothiazines with hydroxyl radicals is most probably the .OH-adduct, PTZH(OH)+.. The mechanism of the .OH-radical-induced oxidation of phenothiazines suggested in an earlier publication has been confirmed and enlarged.",
author = "Detlef Bahnemann and Asmus, {Klaus Dieter} and Willson, {Robin L.}",
note = "Copyright: Copyright 2015 Elsevier B.V., All rights reserved.",
year = "1983",
doi = "10.1039/P29830001661",
language = "English",
pages = "1661--1668",
journal = "Journal of the Chemical Society, Perkin Transactions 2",
issn = "1472-779X",
publisher = "Chemical Society",
number = "9",
}