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Kinetics and mechanism of formation and decay of 2,2′‐azinobis‐(3‐ethylbenzothiazole‐6‐sulphonate) radical cation in aqueous solution by inorganic peroxides
Author(s) -
Venkatasubramanian Lakshmanan,
Maruthamuthu Pichai
Publication year - 1989
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550210604
Subject(s) - chemistry , abts , hydrogen peroxide , dication , kinetics , radical ion , aqueous solution , peroxide , photochemistry , medicinal chemistry , inorganic chemistry , organic chemistry , ion , antioxidant , dpph , physics , quantum mechanics
The kinetics of oxidation of 2,2′‐azinobis‐(3‐ethylbenzothiazole‐6‐sulphonate) (ABTS) by the inorganic peroxides, peroxomonosulphate, peroxodisulphate, peroxodiphosphate, and hydrogen peroxide were investigated in aqueous solution. The kinetics of formation of the radical cation, ABTS .+ , on one‐electron abstraction by these peroxides and the further reaction of ABTS .+ with higher concentrations of these peroxides at longer time scale were studied by following the growth and decay of the radical cation, ABTS .+ at 417 nm. The rate of formation of ABTS .+ was found to obey a total second‐order, first‐order each in [ABTS] and [peroxide], except for H 2 O 2 , which reacted through Michaelis‐Menten kinetics. All the peroxides investigated were found to react with ABTS .+ ; however peroxodisulphate alone oxidized ABTS .+ to the dication (ABTS ++ ), the other peroxides reacted via ionic mechanism, probably forming sulphoxide and sulphone as products. The kinetics of decay of the radical cation, ABTS .+ , was also found to follow a total second‐order, first‐order each in [ABTS .+ ] and [peroxide], except peroxodiphosphate the reaction of which obeyed Michaelis‐Menten kinetics. The effect of pH and temperature were also investigated in all the systems and the kinetic and thermodynamic parameters were evaluated and discussed with suitable reaction mechanisms.