Publication Type
Journal Article
UWI Author(s)
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
Medium Designator
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Connective Phrase
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Journal Title
Journal of the Chemical Society. Dalton Transactions
Translated Title
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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
Language
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Connective Phrase
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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 £ 35.1°C, 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 25°C 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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Keywords
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