Kinetics and mechanism of the reduction of gold(III) by glycine in acetate buffer

Sen, Pratik; Gani, Nasimul; Midya, Jayanta K.; Pal, Biswajit

doi:10.1007/s11243-007-9019-x

Cited by 19 publications

(38 citation statements)

References 35 publications

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“…, and 298 K, respectively. As with the previous investigations with glycine [22] and alanine [23], a similar retarding effect of Cl − was observed (Fig. 4a).…”

Section: Effect Of Ionic Strengthsupporting

confidence: 91%

“…The involvement of a similar short-lived Au(III) intermediate complex has already been reported in earlier investigations [22,23,42]. (13) where k is the rate constant for the slow ratedetermining step.…”

Section: Discussionsupporting

confidence: 65%

“…The rate was found to be enhanced with increasing ionic strength (Table II), and a plot of log k obs vs. μ 1/2 (Brønsted-Bjerrum plot) was linear (R 2 = 0.95) with a positive slope (0.22). involving the oxidation of glycine [22] and alanine [23] by gold(III), in the present case, with an increase in [H + ] the rate first increases and passes through a maximum and then decreases (Fig. 3).…”

Section: Effect Of Ionic Strengthsupporting

confidence: 50%

“…However, there are only a few reports of reactions of gold(III) with amino acids [19][20][21]. Recently, we have investigated the oxidation of glycine [22] and alanine [23] by gold(III) where both the amino acids were neutral. L-Glutamic acid contains an extra carboxylic acid group in addition to the one adjacent to the NH 2 group.…”

Section: Introductionmentioning

confidence: 99%

“…It is, therefore, interesting to investigate which of the carboxylic center of glutamic acid actually acts as a nucleophile and attacks the gold(III) species. Also, it remains to be studied whether the reaction pattern for the oxidation of acidic amino acid is the same as or different from that of the oxidation of the two neutral amino acids glycine [22] and alanine [23]. Moreover, owing to the presence of an extra CH 2 group in glutamic acid compared to glycine and alanine, there may be some additional effects on the redox reaction.…”

Section: Introductionmentioning

confidence: 99%

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

Sen

Gani

Midya

et al. 2012

Int J of Chemical Kinetics

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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.

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“…, and 298 K, respectively. As with the previous investigations with glycine [22] and alanine [23], a similar retarding effect of Cl − was observed (Fig. 4a).…”

Section: Effect Of Ionic Strengthsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 65%

Section: Effect Of Ionic Strengthsupporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Sen

Gani

Midya

et al. 2012

Int J of Chemical Kinetics

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A Computational Mechanistic Investigation into Reduction of Gold(III) Complexes by Amino Acid Glycine: A New Variant for Amine Oxidation

Chipman

Gouranourimi

Farshadfar

et al. 2018

Chemistry A European J

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Density functional theory (DFT) was utilized to explore the reduction of gold(III) complexes by the amino acid glycine (Gly). Interestingly, when the nitrogen atom of Gly coordinates to the gold(III) center, its C -hydrogen atom becomes so acidic that it can be easily deprotonated by a mild base like water. The deprotonation converts the amino acid into a potent reductant by which gold(III) is reduced to gold(I) with a moderate activation energy. To our knowledge, this is the first contribution suggesting that primary amines are oxidized to imines via direct α-carbon deprotonation. This finding may provide new insights into the mechanistic interpretation of amine oxidations catalyzed/mediated by a center with high cathodic reduction potential. This work also provides a rationalization behind why gold(III) complexes with amine-based polydentate ligands are reluctant to undergo a redox process. Gold(III) reduction occurs most efficiently if the C proton leaves in the plane of the C , N and Au atoms. Chelation prevents this alignment, resulting in the gold(III) complex being unreactive toward reduction. It has been experimentally found that gold(III) is capable of oxidizing Gly to glyoxylic acid (GA) as the initial product. The latter, in the presence of another gold(III) complex, has been reported to undergo oxidative decarboxylation to afford CO and HCOOH. This process is found to be mediated by formation of a geminal diol intermediate produced by reaction of water with the aldehyde functional group of the coordinated GA.

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Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processes

Sen

Gani

Midya

et al. 2009

Int J of Chemical Kinetics

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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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Kinetics and mechanism of the reduction of gold(III) by glycine in acetate buffer

Cited by 19 publications

References 35 publications

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

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

A Computational Mechanistic Investigation into Reduction of Gold(III) Complexes by Amino Acid Glycine: A New Variant for Amine Oxidation

Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processes

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