Pulse Radiolysis Studies of the Oxidation of Phenols by ⋅SO 4 - and Br 2 - in Aqueous Solutions

Publisher Website
Google Scholar
Abstract
The reactions of .**GRAPHIC**. and .**GRAPHIC**. with phenol, o-, m- and p-cresol, and tyrosine were studied by pulse radiolysis methods using optical absorption and conductometric detectors. The reaction of .**GRAPHIC**. with the undissociated phenols was very rapid; in the case of tyrosine the rate constant was measured to be (3.0 .+-. 0.2) .times. 109 M-1 s-1. With tyrosine, formation of the phenoxyl radical was complementary to the disappearance of .**GRAPHIC**. with no intermediate having a lifetime > 0.1 .mu.s being possible. The reaction proceeds most probably by a direct oxidative electron transfer from the phenol. Reaction of Br2- with the phenoxide ions gave similar spectra. Calculated extinction coefficients based on reaction of .**GRAPHIC**. and .**GRAPHIC**. agreed to within the experimental error of .+-. 5%. Conductometric experiments (SO4- reaction) showed identical behavior for all phenols in near neutral solution with exactly the same yield of strong acid produced as when .**GRAPHIC**. abstracts from CH3OH. Thus, quantitative direct oxidation to a phenoxyl radical must occur in each case.

This publication has 1 reference indexed in Scilit: