Premium
Formation of a promazine radical and promazine 5‐oxide in the reaction of promazine with hydrogen peroxide: Mechanistic insight from kinetic and EPR measurements
Author(s) -
Wiśniewska Joanna,
Wrzeszcz Grzegorz,
Koter Stanisław
Publication year - 2010
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20454
Subject(s) - promazine , chemistry , radical , photochemistry , electron paramagnetic resonance , hydrogen peroxide , reaction rate constant , kinetics , organic chemistry , nuclear magnetic resonance , medicine , physics , chlorpromazine , quantum mechanics , endocrinology
The kinetics of the oxidation of promazine (PMZ) by hydrogen peroxide was studied in the presence of a large excess of H 2 O 2 in acidic chloride media using UV–vis spectroscopy. The reaction proceeds via two consecutive steps. In the first step, oxidation leads to formation of a promazine radical. In the second step, the promazine radical is oxidized to promazine 5‐oxide. Electron paramagnetic resonance spectroscopy (EPR) results provide clear evidence for the formation of an intermediate promazine radical. Linear dependences of the pseudo‐first‐order rate constants ( k 1 and k 2 ) on [H 2 O 2 ] with a nonzero intercept were established for the first and the second process, respectively. The rate of the first stage of the reaction increased slightly with increasing concentration of O 2 , indicating the role of the OH • radicals on the redox process, which are transformed into the Cl 2 −•radicals. The mechanism of the overall reaction is discussed on the basis of all these kinetic measurements. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 1–9, 2010