The oxidation of thymol and carvacrol to thymoquinone with potassium peroxymonosulfate (KHSO5) catalyzed by iron phthalocyanine tetrasulfonate (FePcTS) in a methanol (4.0 mL)-water (0.5 mL) mixture has been carried out. In a typical reaction, the amounts of the substrate, oxidant, and catalyst were 0.300, 0.600, and 1 x 10(-3) millimoles, respectively. Ninety-nine percent conversions of thymol in 1 h and of carvacrol in 30 min were achieved at ambient temperature. The major product of both oxidation reactions was thymoquinone (2-isopropyl-5-methylbenzoquinone, TQ) and the reactions also yielded polymeric products poly(2-isopropyl-5-methyl-1,4-phenylene oxide) and poly(5-isopropyl-2-methyl-1,3-phenylene oxide). These polymers are novel and not reported before. When H2O2 or Bu (t) OOH was used as the oxidant, the yield of TQ was < 1 %.