The kinetics and spectral characteristics of the transients formed in the reactions of
•OH and
•N
3 with quinoxalin-2(1
H)-one (Q), its methyl derivative, 3-methylquinoxalin-2(1
H)-one (3-MeQ) and pyrazin-2-one (Pyr) were studied by pulse radiolysis in aqueous solutions at
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The kinetics and spectral characteristics of the transients formed in the reactions of
•OH and
•N
3 with quinoxalin-2(1
H)-one (Q), its methyl derivative, 3-methylquinoxalin-2(1
H)-one (3-MeQ) and pyrazin-2-one (Pyr) were studied by pulse radiolysis in aqueous solutions at pH 7. The transient absorption spectra recorded in the reactions of
•OH with Q and 3-MeQ consisted of an absorption band with λ
max = 470 nm assigned to the OH-adducts on the benzene ring, and a second band with λ
max = 390 nm (for Q) and 370 nm (for 3-MeQ) assigned,
inter alia, to the N-centered radicals on a pyrazin-2-one ring. The rate constants of the reactions of
•OH with Q and 3-MeQ were found to be in the interval (5.9–9.7) × 10
9 M
–1·s
–1 and were assigned to their addition to benzene and pyrazin-2-one rings and H-abstraction from the pyrazin-2-one nitrogen. In turn, the transient absorption spectrum observed in the reaction of
•N
3 exhibits an absorption band with λ
max = 350 nm. This absorption was assigned to the N-centered radical on the Pyr ring formed after deprotonation of the respective radical cation resulting from one-electron oxidation of 3-MeQ. The rate constant of the reaction of
•N
3 with 3 MeQ was found to be (6.0 ± 0.5) × 10
9 M
–1·s
–1. Oxidation of 3-MeQ by
•N
3 and Pyr by
•OH and
•N
3 confirms earlier spectral assignments. With the rate constant of the
•OH radical with Pyr (
k = 9.2 ± 0.2) × 10
9 M
–1·s
‒1, a primary distribution of the
•OH attack was estimated nearly equal between benzene and pyrazin-2-one rings.
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