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Effect of microheterogeneous environments of CTAB, Triton X‐100, and Tween 20 on the oxidative degradation of d ‐fructose by nanoparticles of MnO 2
Author(s) -
Midya Jayanta K.,
Ghosh Dinesh C.,
Pal Biswajit,
Sen Pratik K.
Publication year - 2019
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.21239
Subject(s) - chemistry , micelle , inorganic chemistry , fructose , aqueous solution , nanoparticle , ammonium bromide , chemical engineering , pulmonary surfactant , organic chemistry , engineering , biochemistry
The kinetics of the oxidative degradation of d ‐fructose by nanoparticles of MnO 2 has been studied in dilute sulfuric acid medium and also in the presence of surfactants of cetyl trimethyl ammonium bromide (CTAB), Triton X‐100 (TX‐100), and Tween 20. Amorphous nanoparticles of MnO 2 in the form of spherical particulates of size 50–200 nm, as detected by a transmission electron microscope, have been found to exist, supported on two‐dimensional gum acacia sheets. The reaction is first order in MnO 2 but complex order with respect to fructose and H + . The reaction is inhibited due to adsorption of reaction products on the surface of MnO 2 nanoparticles. The reaction takes place through an intermediate complex formation between β‐ d ‐fructopyranose and protonated MnO 2 . A one‐step two‐electron transfer reaction ultimately leads to the formation of an aldonic acid and formic acid. The entropy of activation plays the key role for the reaction in the absence of surfactants. In the surfactant‐mediated reaction, partitioning of both the reactants takes place between the aqueous and micellar pseudophases and reaction occurs following Berezin's model. Binding of fructose with the surfactants in the Stern/palisade layer takes place through the ion–dipole interaction and H‐bonding while protonated MnO 2 remains at the outer side of the Stern/palisade layer within the micelle. Both the enthalpy and entropy changes associated with the fructose–water interaction, fructose–micelle interaction, and micelle–water interaction finally control the fructose–micelle binding.