Modeling antioxidant properties of polyphenols by the TEMPO-initiated reaction of 3,5-di-tert-butylcatechol with dioxygen

The oxidation reaction of 3,5-di-tert-butylcatechol (dbcatH2) with dioxygen to 3,5-di-tert-butyl-o-benzoquinone (dbq) initiated by 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) has been investigated in methanol and CCl4 at ambient temperature. The oxidation of dbcatH2 was followed by electron spectroscopy and the rate constants were determined according to the rate law −d[dbcatH2]/dt = kobs [dbcatH2][TEMPO][O2]. The rate constant, activation enthalpy and entropy at 323 K are as follows: kobs (M−2 s−1) = 1.58 ± 0.03, ΔH‡ = 51 ± 10 kJ mol−1 and ΔS‡ = −84 ± 32 J mol−1 K−1.