The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc-AcOH buffer in the pH range 3.73-4.77. The reaction is first order with respect to both Au(III) and glycine. Both H + and Cl -ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium. AuCl 4 -and AuCl 3 (OH) -are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product by 1 H NMR spectroscopy.

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by 1 H NMR spectroscopy. Under the experimental conditions, AuCl − 4 and AuCl 3 (OH) − are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H + and Cl − on the secondorder rate constant k 2 have been analyzed, and accordingly the rate law has been deduced:. Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed.

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The effect of nonionic micelles of Triton X-100 on the oxidative decarboxylation of L-glutamic acid by chloroaurate(III) complexes has been investigated in acetate buffer medium. The reaction is first order with respect to Au(III), but a complex order with respect to glutamate. H + ion has both accelerating and retarding effects in the pH range 3.72-4.80, whereas a Cl − ion has an inhibiting effect in the range 0.02-0.56 mol dm −3 . Under the experimental conditions, AuCl − 4 and AuCl 3 (OH) − are the predominant and effective oxidizing species, whereas the zwitterion (H 2 A) and mononegative anion (HA − ) are the predominant reducing species of the amino acid. The reaction involves a one-step two-electron transfer process and passes through the intermediate formation of iminic cation. In the presence of surfactant, the reaction passes through a maximum and it appears to follow Berezin's model, where both the oxidant and the substrate are partitioned between the aqueous and the micellar phase and then react. The binding constants between the reactants and the surfactant have been evaluated at different temperatures. Compensation between substrate-water interaction and substrate-micelle interaction plays an important role in such redox reactions in the presence of a surfactant.

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 -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.