Abstract A study was carried out on the kinetics of free-radical chain oxidation of 1-isopropyl- 4-methoxybenzene (1a) and 1-ethyl-4-methoxybenzene (1b) with oxygen in the liquid phase to yield 1-methyl-1-(4-methoxyphenyl) ethyl hydroperoxide (2a) and 1-(4-methoxyphenyl) ethyl hydroperoxide (2b). The oxidizability of 1a and 1b was studied over the temperature range 50–100 C. Long-term oxidations of 1a and 1b to the corresponding hydroperoxides ...