F. Bonnichon et al., AFTER-EFFECT IN THE OXIDATION OF HYDROQUINONE PHOTOINDUCED BY COBALT AZIDE COMPLEX, Journal of photochemistry and photobiology. A, Chemistry, 109(3), 1997, pp. 217-222
The mechanism of the oxidation of hydroquinone (QH(2)) photoinduced by
the azide complex has been studied in aqueous acidic solution. Such a
n oxidation is shown to proceed selectively through an electron transf
er reaction producing the semiquinone radical. 1,4-Benzoquinone (Q) ap
pears to be the primary product in the presence and in the absence of
oxygen. The ratios [Co(II)](form)/[QH(2)](disap) and [Q](form)/[QH(2)]
(disap) are found to be equal to 2 and 1, respectively. This fits well
with the disproportionation of the semiquinone radical. The resulting
quinone is unstable in acidic medium and reacts with the azide anion
(N-3(-)) to generate azidohydroquinone and azidobenzoquinone. An overa
ll mechanism describing the photochemical and the dark reaction has be
en established. (C) 1997 Elsevier Science S.A.