Studies on electron transfer reactions: reduction of heteropoly 11-tungstophosphovanadate(V) by l-cysteine and thioglycolic acid in aqueous acid medium

The rates of the electron transfer reaction of l -cysteine and thioglycolic acid with the polyoxometalate, [PV V W 11 O 40 ] 4− , have been measured spectrophotometrically in aqueous acid medium. The polyoxometalate oxidizes cysteine to cystine and thioglycolic acid to dithioglycolic acid and gets r...

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Bibliographic Details
Published in:Transition metal chemistry (Weinheim) 2009-10, Vol.34 (7), p.733-737
Main Authors: Sami, Ponnusamy, Venkateshwari, Kandasamy, Mariselvi, Natarajan, Sarathi, Arunachalam, Rajasekaran, Kasi
Format: Article
Language:English
Subjects:
Acids
Catalysis
Chemistry
Chemistry and Materials Science
Electron transfer
Electron transfer reactions
Inorganic Chemistry
Organometallic Chemistry
Physical Chemistry
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Summary:The rates of the electron transfer reaction of l -cysteine and thioglycolic acid with the polyoxometalate, [PV V W 11 O 40 ] 4− , have been measured spectrophotometrically in aqueous acid medium. The polyoxometalate oxidizes cysteine to cystine and thioglycolic acid to dithioglycolic acid and gets reduced to heteropoly blue, [PV IV W 11 O 40 ] 5− . The order of the reaction with respect to oxidant is one, whereas the reaction shows second order dependence on the substrates. The rate–pH profile shows that both the unionized and ionized thiol groups of the substrates are active species involved in electron transfer. A suitable mechanism has been proposed for the title reaction based on the results of kinetic studies.
ISSN:0340-4285
1572-901X
DOI:10.1007/s11243-009-9255-3