Natural phenolic compounds in the reaction with a nitrogen-centered radical in an aprotic solvent

Kinetics and mechanism of the reaction of vegetable phenols (PhOH) with 2,2'-diphenyl-1-picrylhydrazyl radical (DPPHaEuro cent) in a polar aprotic solvent, dimethyl sulfoxide, were studied. The reaction of natural phenols with DPPHaEuro cent in dimethyl sulfoxide occurs in two stages. In the first stage, a proton-coupled electron transfer (PCET) occurs from a PhOH molecule to DPPHaEuro cent to give primary transformation products, phenoxyl radicals (PhOaEuro cent) and diphenyl hydrazine (DPPH-H), and in the second, the hydrazyl radical is consumed in the reaction with PhOaEuro cent transformation products, enolized dimers, which is confirmed by NMR spectroscopy. A relationship was revealed between the antiradical activity of phenols in the reaction with DPPHaEuro cent (ln k) and the ionization potential of the phenolates being formed.