Pulse radiolytic one-electron oxidation of some dihydroxy-substituted anthraquinones

Pal, Haridas ; Palit, Dipak K. ; Mukherjee, Tulsi ; Mittal, Jai P. (1992) Pulse radiolytic one-electron oxidation of some dihydroxy-substituted anthraquinones Journal of the Chemical Society, Faraday Transactions, 88 (5). pp. 681-687. ISSN 0956-5000

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Official URL: http://pubs.rsc.org/en/Content/ArticleLanding/1992...

Related URL: http://dx.doi.org/10.1039/FT9928800681


The spectroscopic characteristics and the kinetic parameters associated with the transients formed on one-electron oxidation of quinizarin (1,4-dihydroxy-9, 10-anthraquinone), quinizarin 2- and 6-sulfonates, 1,5-dihydroxy-9, 10-anthraquinone and 1,8-dihydroxy-9, 10-anthraquinone have been studied by pulse radiolysis and kinetic spectrophotometric techniques, using OH, O•-, N3, Br and CH2CHO as the oxidising radicals. The pKa and the disproportionation equilibria of the semi-oxidised quinones have been studied for the water-soluble sulfonates. In contrast to the complex decay of the semi-oxidised naphthazarin (5,8-dihydroxy-1,4-naphtho-quinone), the semi-oxidised anthraquinone derivatives decay by simple second-order kinetics. The pKa values of the latter are also much higher (ca. 8) compared to the former (ca. <4). The differences observed are attributed to the loss in symmetry in the free radical structures of the semi-oxidised anthraquinone derivatives.

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