✍ Scribed by Wei-Lin Chen; Wei-Shuen Li; Ping-Jou Fu; Andrew Yeh
No coin nor oath required. For personal study only.
A kinetic study of the reduction of pyrocatechol and catechin by dpph^•^ radical has been carried out in various ratios of CH~3~OH/H~2~O mixed solvent at pH 5.5–7.5, μ = 0.10 M [(n‐Bu)~4~N]ClO~4~, and T = 25°C. The rate constants of oxidation in aqueous solvent, k, were obtained from the extrapolation of the linear plots of the specific rate constants k vs. % H~2~O plots at each pH value. A linear relationship between k and 1/[H^+^] was observed for both flavonoids with k = k~1~K~a1~/[H^+^], where K~a1~ was the first acid dissociation constant on the catechol ring and k~1~ is the rate constant of the oxidation of the mononegative species HX^−^. The values of k~1~ obtained from the slopes of the plots are (8.2 ± 0.2) × 10^5^ and (6.1 ± 0.1) × 10^5^ M^−1^ s^−1^ for pyrocatechol and catechin, respectively. The analysis of the reaction on the basis of Marcus theory for an outer‐sphere electron transfer reaction yielded a value of 3.7 × 10^3^ M^−1^ s^−1^ for the self‐exchange rate constant of dpph^•^/dpphH couple. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 147–153, 2011
📜 SIMILAR VOLUMES
Selective protection of the catechol ring of catechin has been achieved. From this key compound, catechin analogues protected either on the catechol or the resorcinol rings were synthesized. From these analogues, phenoxyl radicals on the catechol or on the resorcinol rings were produced by photo-oxi