| Summary: | 碩士 === 東海大學 === 化學系 === 96 === The reactions of catechin and rutin with Ru(NH3)5L3+ (L = pyrazine, pz; isonicotinamide, isn) complexes underwent a two electron oxidation. 1H-NMR spectra further suggested that oxidation went to the B ring (catechol ring) of the flavonoids with the formation of quinone products. The kinetics of the oxidation carried out at pH = 4.0 – 7.6 suggested that the reaction proceeded through an one electron oxidation of flavonoids in the form of HX- (k1) and X2- (k2) by Ru(NH3)5L3+ complexes to form the corresponding semiguinone radicals, followed by the rapid scavenge of the radicals by Ru(NH3)5L3+ complexes to form the final products. The specific rate constants were measured and the results are – catechin: k1 = 1.62 × 107 M-1s-1 (L = pz) and k1 = 2.26 × 106 M-1s-1, k2 = 1.5 × 1011 M-1s-1 (L = isn); for the oxidation of rutin are: k1 = 7.32 × 106 M-1s-1, k2 = 7.47 × 1010 M-1s-1 (L = pz) and k1 = 1.26 × 106 M-1s-1, k2 = 4.7 × 1010 M-1s-1 (L = isn), at μ = 1.0 M LiClO4, T = 25 °C. After the correction of rate constants for the contribution of equilibrium barrier (kncorr = kn /√K , n = 1, 2), the intrinsic reactivities of both catechin and rutin were found to be greater than those of the ascorbic acid by more than an order of magnitude for the two forms of reductants.
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