Peroxyesters As Precursors to Peroxyl Radical Clocks

The reactions of peroxyl radicals are at the center of the oxidative degradation of essentially all petroleum-derived hydrocarbons and biological lipids and consequently, the inhibition of these processes by radical-trapping antioxidants. Recently described peroxyl radical clocks offer a simple, convenient, and inexpensive method of determining rate constants for H-atom transfer reactions to peroxyl radicals, greatly enabling the kinetic and mechanistic characterization of compounds with antioxidant properties. We follow up our preliminary communication on the development of a methodology utilizing <i>tert</i>-butyl styrylperacetate as a precursor to a versatile peroxyl radical clock with the present paper, wherein we describe a novel naphthyl analogue, which provides for much improved product resolution for analysis, and provide the complete details associated with its development and application. Using this new precursor, and with consideration of the expanded set of reaction products, inhibition rate constants were measured for a variety of representative phenolic and diarylamine radical-trapping antioxidants. We also provide details for the use of this methodology for the determination of mechanistic information, such as kinetic solvent effects, Arrhenius parameters, and kinetic isotope effects