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Holder Alvin A. Brown Ross F. G. Marshall Sophia C. Payne Vince C. R. Cozier Maria D. Alleyne Walter A. Bovell Christopher O. 《Transition Metal Chemistry》2000,25(5):605-611
A detailed investigation of the oxidation of L-ascorbic acid (H2A) by the title complex has been carried out using conventional spectrophotometry at 510 nm, over the ranges: 0.010 [ascorbate]
T
0.045 mol dm–3, 3.62 pH 5.34, and 12.0 30.0 °C, 0.50 I 1.00 mol dm–3, and at ionic strength 0.60 mol dm–3 (NaClO4). The main reaction products are the bis(pyridine-2,6-dicarboxylate)cobaltate(II) ion and l-dehydroascorbic acid. The reaction rate is dependent on pH and the total ascorbate concentration in a complex manner, i.e., k
obs = (k
1
K
1)[ascorbate]
T
/(K
1 + [H+]). The second order rate constant, k
1 [rate constant for the reaction of the cobalt(III) complex and HA–] at 25.0 °C is 2.31 ± 0.13 mol–1 dm3 s–1. H
= 30 ± 4 kJ mol–1 and S
= –138 ± 13 J mol–1 K–1. K
1, the dissociation constant for H2A, was determined as 1.58 × 10–4 mol dm–3 at an ionic strength of 0.60 mol dm–3, while the self exchange rate constant, k
11 for the title complex, was determined as 1.28 × 10–5 dm3 mol–1 s–1. An outer-sphere electron transfer mechanism has been proposed. 相似文献
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