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Publication Type
Journal Article
Author, Analytic
Sadler-McKnight, N.,; Dixon, D.; Dasgupta, Tara, P
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Article Title
Oxidation of biological substrates by chromium (VI) Part 1.: Mechanism of the oxidation of L-ascorbic acid in aqueous solution
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Journal Title
Journal of the Chemical Society. Dalton Transactions
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Reprint Status
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Date of Publication
1993
Volume ID
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Issue ID
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Page(s)
3489-3495
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Location/URL
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ISSN
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Notes
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Abstract
The kinetics of oxidation of L-ascorbic acid (H2A) by potassium chromate has been studied under aerobic and anaerobic conditions over the range 0.002 [A]T 0.040 mol dm-3, 3.50 pH 8.70, 17.8 T 35.1C, 0.06 I 0.50 mol dm-3 (NaC1O4) and 0.05 [O2] 0.12 mmol dm-3. The experimental rate constant obtained in the presence of oxygen are about 10 times smaller than those obtained in its absence. A mechanism involving the formation of a chromium (VI)-ascorbate-oxygen intermediate is discussed in an attempt to explain this. The disappearance of chromium (VI) under aerobic conditions follows the rat law (i) where kt = (k1Ka1[H+] + k2Ka1Kc + k3[H+]2)/(Ka1 + [H+]) (Kc + [H+]). -d[CrVI]/dt = kf[A]T[CrVI]T At 25C and I = 0.50 mol dm-3 (NaC1O4), k1 = 59.4 0.5, k2 = 0.10 0.02 and k2 = 115 dm3 mol-1 s-1....
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