We have observed that the debutylation reaction can readily occur when 2,5-di-t-butyl-p-dimethoxybenzene (1) was mixed with perfluorocarboxylic acids or with AlCl 3 CH 2 Cl 2 system, but did not occur with aqueous HI or HBF 4 or absolute trichloroacetic acid. EPR observation shows that radical intermediates were generated in the former systems, but not in the latter case. Kinetic study indicates that the reaction of substrate 1 with trifluoroacetic acid behaves third-order kinetics, second in 1 and first in the acid. All the results reveal that an intrinsic relation may exist between the debutylation and the formation of the radical intermediates.