Effects of nonionic micellar aggregates on the electron transfer reaction between l‐glutamic acid and gold(III) complexes

Abstract

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.

Evidence of co-operativity in the pre-micellar region in the hydrolytic cleavage of phenyl salicylate in the presence of cationic surfactants of CTAB, TTAB and CPC

“…[1][2][3]. Micelles can act as microreactors where the reactants are partitioned by means of electrostatic and/or hydrophobic interactions and thus modify the reaction rates and equilibria [4][5][6][7][8][9]. Micellar catalyzed reactions may be compared to those catalyzed by enzymes since the hydrophobic interactions within the micelle have some similarities with the complex reactions occurring in biological assemblies [10,11].…”

Oxidative Degradation ofl-Isoleucine by Au3+Complexes in Weakly Acid Medium: A Kinetic and Mechanistic Investigation

“…This electrostriction phenomenon is another factor responsible for highly negative Δ S # . In several earlier reports involving the oxidation of amino acids such highly negative ΔS # were also noted.…”

Evidence of formation of dye–surfactant ion pair micelle in the anionic surfactant mediated alkaline fading of methyl violet carbocation

“…Surfactant molecules are amphiphilic in nature consisting water‐soluble or insoluble moiety, which interacts as monomer 34,35 or micelles 36,37 through electrostatic or hydrophobic interactions and thus catalyze or inhibit the rate of different chemical reactions. Anionic surfactant monomers often interact with the carbocation dye and influence the rate of the fading reaction even in submicellar concentrations 18 .…”