Kinetic and mechanistic studies on the reactions of peroxynitrite with estrone and phenols

Reaction of peroxynitrite with estrone, a female sex hormone, was carried out in tetrahydrofuran (THF)/H₂O (8: 2) basic solutions. The major products are the corresponding o-quinone, nitroestrone and 2,2′-biphenol. The reaction of phenols with peroxynitrite under the same conditions leads also to the formation of quinones, nitrophenols and biphenols. The major mechanistic pathways take place via a one-electron oxidation of the phenolic group leading to the formation of a phenoxyl radical intermediate which is further oxidized by peroxynitrite (or by intermediates generated from peroxynitrite) to give the final products. A Hammett correlation of the rate constants for the oxidation of meta substituted phenols support a radical mechanism. The kinetic isotope factors rule out the involvement of a C-H bond cleavage in the rate-determining step. A multistep mechanism showing major intermediates involved in the reaction and the final products has been proposed. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 1, pp. 96–105. The article is published in the original.