Peroxyl radical clocks

A series of peroxyl radical clocks has been developed and calibrated based on the competition between the unimolecular beta-fragmentation (kbeta) of a peroxyl radical and its bimolecular reaction with a hydrogen atom donor (kH). These clocks are based on either methyl linoleate or allylbenzene and were calibrated directly with alpha-tocopherol or methyl linoleate, which have well-established rate constants for reaction with peroxyl radicals (kH-tocopherol: 3.5 x 106 M-1 s-1, kH-linoleate: 62 M-1 s-1). This peroxyl radical clock methodology has been successfully applied to determine inhibition and propagation rate constants ranging from 100 to 107 M-1 s-1.