Free radical reactions of the phenothiazine, metiazinic acid

authored by

Detlef Bahnemann, Klaus Dieter Asmus, Robin L. Willson

Abstract

Absolute rate constants have been measured for the reaction of the anionic conjugate base of metiazinic acid, MZ^-, in the pH range 8-11, with hydrated electrons (k 1.5 × 10⁹ | mol^-1 s^-1), and for the oxidation of MZ^- by OH^., Br₂^-., (SCN)₂^-., CO₃^-., Tl(OH)₂, N₃,^{. .}CH₂CHO, (CH₃SCH₃)₂^+., CH₃SSCH₃^+. and lipoate^+.. The k values for these oxidations are found to be in the 10⁹-10¹⁰ | mol^-1 s^-1 range, except for k(^.CH₂CHO + MZ^-) 2 × 10⁸ | mol^-1 s^-1. The oxidation of metiazinic acid leads to MZ^±. radical zwitterions with yields ranging from 50 to 100% with the minimum value referring to the oxidation by ^.CH₂CHO. The MZ^±. radical zwitterion is characterized by two strong optical absorption bands with maxima at 530 (ε 11 000 | mol^-1 cm^-1) and 270 nm (51 500). Other primary oxidation products are indicated, but only a transient absorption around 350 nm (OH^. adduct and/or hydrogen abstraction product) could qualitatively be identified in the reaction of metiazinic acid with hydroxyl radicals.

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

890-895

No. of pages

6

ISSN

1472-779X

Publication date

1981

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Chemistry(all)

Electronic version(s)

https://doi.org/10.1039/P29810000890 (Access: Unknown)