ESR and pulse radiolysis studies of the acid-base properties of the m-benzosemiquinone radical anion

摘要: The 3-hydroxyphenoxyl radical, the conjugate acid of m-benzosemiquinone radical anion, examined by in situ radiolysis-ESR methods at pH 4.0 exhibits a difference between hyperfine constants protons C/sub 4/ and 6/ positions, 11.21 G vs. 8.69 G, respectively. This is not manifest studies more acidic solutions where are averaged as result proton exchange. While total unpaired spin population on ring similar to that for phenoxyl there an appreciable shift away from OH group. In near neutral, exchange basic forms slow contributions both anion apparent. pK/sub a/ dissociation this found be 6.43 +/- 0.05 ESR optical absorption dependence relative its forms. 3 units below lowest radical's parent compound, resorcinol. Phosphate can used catalyze equilibration so above 0.1 M phosphate only singlemore » spectrum representing weighted average observed.« less