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

摘要

The oxidation reaction of 3,5-di-tert-butylcatechol (dbcatH_2) 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 CCl_4 at ambient temperature. The oxidation of dbcatH_2 was followed by electron spectroscopy and the rate constants were determined according to the rate law -d[dbcatH_2]/dt = k_(obs) [dbcatH_2][TEMPO][O_2]. The rate constant, activation enthalpy and entropy at 323 K are as follows: k_(obs)(M~(-2) s~(-1)) = 1.58 ± 0.03, ΔH = 51 ± 10 kJ mol~(-1) and ΔS = -84 ± 32 J mol~(-1) K~(-1).