KINETICS AND MECHANISM OF OXIDATION OF D-GLUCOPYRANOSE 6-PHOSPHATE AND D-RIBOFURANOSE 5-PHOSPHATE BY VANADIUM(V) IN PERCHLORIC ACID MEDIA
The second-order rate constants for the oxidations of D-glucopyranose 6-phosphate and D-ribofuranose 5-phosphate by vanadium(V) in perchloric acid media have been measured spectrophotometrically in the visible region.The order with respect to +> is less than unity for each reaction.The enthalpy and entropy of activations of the reactions are higher than those for the corresponding two-electron oxidations by chromium(VI).The oxidations involve free-radical intermediates.
Gupta, Kalyan Kali Sen,Gupta, Shipra Sen,Mandal, Subrata Kumar,Basu, Samarendra Nath
Reactivity of some sugars and sugar phosphates towards gold(III) in sodium acetate-acetic acid buffer medium
The kinetics of the oxidation of some aldoses and aldose phosphates have been studied spectrophotometrically in sodium acetate-acetic acid buffer medium at different temperatures. The reactions are first order with respect to [Au(III)] and [substrate]. Both H+ and Cl- ions retard the reaction. The reactions appear to involve different gold(III) species, viz. AuCl4/-, AuCl3(OH2) and AuCl3(OH)-. The results are interpreted in terms of the probable intermediate formation of free radicals and Au(II). Aldoses react with gold(III) in the order: triose > tetrose > pentose > hexose. The sugar phosphates react with gold(III) at a faster rate than the parent sugars except glucose-1-phosphate, which reacts at slower rates than glucose. A tentative reaction mechanism leading to the formation of products has been suggested.
Sen Gupta, Kalyan Kali,Pal, Biswajit,Begum, Bilkis Ara
p. 115 - 123
(2007/10/03)
Reactivities of some sugar phosphates towards permanganate in perchloric acid medium and mechanism of the oxidation processes
The reactivities of some sugar phosphates towards permanganate have been examined in perchloric acid medium. The reactions are first order in [sugar phosphate] and [MnO4-]. The rate increases with increase in [H+]. The reactivities follow the order: erythrose 4-phosphate> ribose 5-phosphate> fructose 1,6-diphosphate> glucose 6-phosphate> glucose 1-phosphate. The mechanism of the reactions is discussed.
Sen Gupta, Kalyan Kali,Tribedi, Partha Sarathi,Sen Gupta, Shipra
p. 427 - 430
(2007/10/03)
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