An inactive premicellar/micellar {Surfactant-MnO 4-} aggregate has been found to inhibit the rate of oxidation of disaccharides viz. maltose and lactose by alkaline KMnO 4. The order of reaction in oxidant is unity while that in Substrate and alkali has been found to decrease from unity at higher [Substrate] and [OH-], respectively. The observed rate constants were in order of k aq > k NaLS > k Tx-100 > k CTAB , which has been explained in terms of electrostatic and hydrophobic forces.
ABSTRACT. Anionic (sodium lauryl sulphate, NaLS) cationic (cetyl ammonium bromide, CTAB) and non-ionic (Tween-80) surfactants have been found to inhibit the rate of oxiadation L-proline and L-methionine by alkaline KMnO4. A first order dependence of rate of oxidation was observed with respect to MnO4 − . The order of reaction in substrate and alkali was found to be fractional nearby 0.65 and 0.55 in Aminoacid and OH − , respectively. An aggregation/association between MnO4 − and surfactant has been confirmed spectrophotometrically. A mechanism, involving kinetically inactive [MnO4 − surfactant] aggregate and consistent with kinetic data, has been proposed. The effect of surfactants has been discussed in terms of hydrophobic and electrostatic interactions.
The kinetics of oxidation of reducing sugars viz. D glucose and D fructose by alkaline KMnO 4 in microemulsion media was investigated. The aqueous, cationic microemulsion was prepared from cetyl trim ethyl ammonium bromide, n butanol, n hexane and water, whereas n decane, aerosol OT and water were used to prepare the anionic microemulsion. The order of reaction in oxidant was always found to be unity, while that in substrate and alkali was decreased from unity to zero at higher concentrations substrate and alka lirespectively. On decreasing [H 2 O]/[Surfactant] ratio (increasing surfactant content) in microemulsion, the observed rates constants of oxidation (k obs ) were decreased. The inhibition effect on the rate of oxidation was greater in cationic microemulsion. A mechanism consistent with kinetic data is proposed.
Micro-Raman studies were performed on ion-irradiated oxidized silicon surfaces with different ion energies, ion fluences and subsequent hydrogenation to determine the efficacy and sensitivity for obtaining information on the degree of ion beam-induced damage in very thin (ca. 100 A) layers of silicon subsurface and the top oxide. The variations in the Raman spectra were interpreted in terms of the degree of amorphization produced in the silicon subsurface by the ion beam and depolymerization of the top SO, layer.
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